rear suspension option

[race81]

anyone running a 4-bar left,spring clamped, rh z-link spring on tube,with a fifth arm and spring with shock mounted on it? thinking of trying this combo next year and wondering if its worth the effort?

[mbaker76]

Not that somebody isnt doing it but i personally dont know anybody running a lift arm in a mod. Im not sure it would work very well on slick with the small tires, especially with the LR clamped up. I would like to try it though, just to see what its like. I think the pullbar helps pull the car up on the bars and creates the instant traction needed to help get the car going in the middle of the corner, whereas the late models have a big enough tire they dont need it. Although with the shallow angles i see on pullbars lately, im not sure they are much different than a lift arm would be.

[profab00]

Beg to differ but I have been on a torque arm for 8 years and would not consider anything else unless I could not afford anything other than straight numbered shocks.

[shocks]

you might get away with the fifth arm w/ coilover setup on a momentum track that doesn't go to complete dust in the features, but I don't personally see that setup being able to produce traction as quickly and efficiently as a pullbar setup. Pretty much all chassis builders agree to this as they are all(at least 99%) using pullbars to help build traction on the throttle. The ones that are using a fifth arm are using it for a braking device, which in my opinion is just unneccessary unsprung weight to the car.

I could be wrong, and odds are that somewhere, somebody is making a fifth arm setup work, but they're definitely in the minority, and I've yet to see such a setup anywhere near the front of a big show (ex. USMTS event).

But again, I think the effectiveness of a pullbar on modified tires is pretty obvious to anybody who looks at any of the top chassis builders' cars.

[profab00]

Chassis such as Mastersbilt, Rocket, Warrior, GRT, Bloomquist Chassis, Barry Wright all race on momentum tracks? It's no big deal to me, I hope all mods continue to run a jerk rod.

[shocks]

Chassis such as Mastersbilt, Rocket, Warrior, GRT, Bloomquist Chassis, Barry Wright all race on momentum tracks? It's no big deal to me, I hope all mods continue to run a jerk rod.

can you please show me where I said anything about late model chassis with lift bars only being good on momentum tracks?

[shocks]

What I do know is that TRE, Hughes, Dirt Works, Pierce, Skyrocket, Shaw, GRT, Allen, Hoffman, D&M, etc, etc, etc, all use pullbars over lift bars when it comes to aborbing torque from being on the throttle.

If lift bars were that great on mods, then some of those guys would be using them as those cars make up the majority of the modified market. We've ran tons of USMTS shows, NCRA shows, etc....never seen anyone running a lift bar that was at the front of the pack in one of these shows. Nor have we ever been outran locally by anyone on a lift bar setup.

I know from the LR spring location thread that you feel mods and late models are the same, however I disagree completely. The companies that build both modifieds and late models obviously disagree as well, judging by their current offerings. In my OPINION, saying that they are the same because they're 4 link is like saying all front suspensions are the same because they have ball joints.

so, respectfully (as I can tell from reading your other posts that your not an idiot), we'll stick with a pullbar on a modified until we're allowed to run as much rubber (amongst other things) as a late model. If a lift bar works for you that's great. But I would appreciate it if you will refrain from twisting what I say to try to make me look wrong.

[profab00]

First and foremost, I didn't mean to step on your toes. If your interpretation is that I attempted to twist your opinion to something it wasn't then I apoligize. I didn't mean it to come across that way. My statement was intended to address the racer questioning the torque arm and whether it would work. It does. I build my own chassis and have ran both and the torque arm actually gives up nothing and might actually be faster on most surfaces. It however is not as forgiving on some types of conditions and the driving style used is somewhat different with the torque arm to get the most out of it. This is why in my opinion the chassis manufacturers opt for the jerk rod.

[shocks]

no hard feelings here. I'm here to learn and share information just like yourself i'm sure. I'd be interested to see what it takes to make the 5th arm work, as our endeavors at making it work weren't very successful. It was awesome on big, heavy tracks, but we didn't care for it on dry slick stop and go's. Where we normally have an abundance of forward bite, very quickly, we were not successful in getting the lift bar to build bite quickly. The 5th arm did give some positive results on corner entry on dry slick, but we couldn't build the bite coming out to justify ditching the pullbar setup.

I respect anyone who takes the time to learn about, design, and build their own chassis. Especially with as technical as modified chassis have become. I'm working on a somewhat "home made" chassis of my own right now. Some of the things that i'm doing are some what "out of the box" so we'll see how it works in time. Most of the changes I'm making to the original design are in the front suspension, as I feel that is where modifieds are most lacking. It may be a complete flop, but i'm not really out anything other than some time if such is the case.

[profab00]

Will be at PIR the rest of this month and then to KLMS next month. Hope you can make it down and I'm not hard to find based off my moniker. Come see me and we'll talk.

[profab00]

By the way, much like a late model, when it is as long as it needs to be and shocked correctly and sprung correctly with the adjustment to wedge it mandates, it only gives up on the "day time powder". On "black ice" it actually has more bite. When you figure that one out, please let me know.

[shocks]

I concur that it was better on black than on powder. Our bar was 36" from centerline of heims at rear end mounting point to center of shock/spring. We had a double adjustable shock on it (wasn't legal, but wasn't concerned with getting that particular item teched) and tried 350, 400, and 450lb springs, with the latter being what we were fastest with. The shock seemed best at 4 compression, 5 rebound with 130lbs gas pressure if I'm reading my old notes right.

I do remember that it was much better with the LR floated behind than with the LR clamped in front. Our RR suspension is pretty unique, and I never messed with it during testing the lift bar.

Our conclusion was pretty much what I said in our original post. I'm sure that it can be made to work, and i'm sure someone (yourself in this case) is having good success with it. It was just one of those things for us where we knew what we had with the pullbar, and we couldn't continue trying other things at the time as we weren't winning while we were experimenting.

It might be one of the things we play around with again next season when the local tracks start having "play days".

have a good one

Shocks

[KTM-Lew]

Thought you both might like to see this?

[race81]

theres no need to get in a pissing match, i appreciate everyones opinion and ideas. my car is heavier than most, just wondering if there was any benifit to this setup with my heavy car, compared to a pullbar and heavy car. ive experimented with pullbar lengths(long, short, left to right) and never noticed a substantial change. we even mounted the pullbar short and hooked to a bracket right at the drivers right shoulder but lowerered. i just havent found the light at the end of tunnel so to speak. but ill keep on experimenting! thanks for the replies!

[shocks]

no pissing match here, just some two way clarifications. That's one of the things about communicating through text. It can be hard to tell how to take what someone is saying.

[KTM-Lew]

I was just trying to lighten the mood...:D

[race81]

Works For Me....

[billetbirdcage]

Profab00 isn't the only person to make it work. I know of another guy that won alot of races against most pretty good competition with a torque arm. It took him a little while to figure it out, but after that he went on a terrror.

I have said for years that I feel the torque arm deal would be better overall, but very few have tried it or will take the time to work with it.

Just my opinion

[mbaker76]

Billet,

What do you think it would take to make it work on a mod. I would like to try it, just havent had the time to get it done yet. We have done the brake chain deal, so we have everything ready to bolt in just need to work on the 5th coil setup. Have been trying to figure out whether to run 5th coil with a chain or find something like a 2 way pullbar where you can use 1 spring for 5th and 6th coil.

[race81]

i think im going to try this deal next year, im always trying something different anyway. my first car in 1996 was a mono-leaf-with coil springs and sliders. 5th arm w/slider w/spring and a 90-10- shck mounted at the front. i believe it may work with the right spring combination. back then i was under powered and didnt have much of an understanding on how to drive these things.

[billetbirdcage]

I think the major thing that is going to make this difficult is the large diameter springs you have to use. This will likely make the 5th coil need to be too far to the right of the driveshaft (just for clearance) and will likely cause the RF to slide under throttle.

My personal opinion is a 2 way pullbar has NO place on any racecar but an asphalt car. Anytime the brake and decell forces are transfered thru the pulbar (downward angle to the frame) it will try to lift the rear end and make the car looser on entry. If that is a common problem for you then one may help. The car would be more consistant without it because you always don't or can't use the same amount of engine or brake braking throughout the race (lap traffic or whatnot). With a torque arm and a bushing/spring to control the engine decell or barke forces the car will be tighter on entry and more constistant over the different stages of a race (leading, following, or lapping cars).

Second thing is a torque arm (for the most part) is lifting on the chassis and not transferring forces to the rear end that is pushing forward or backwards on the rear end, like a pull bar does. A pull bar is pulling on the devise but because it is running forward it also tries to shove the rearend forward as the pullbar get flatter. That force is very strong, so you now have alot more force on the 4-link bars then a torque arm will. This make it alot easier to climb the bars and is most of the reseason you see less bar angle ran on a car will a pull bar car then a toque arm car. A rayburn would likely not hike up if it wasn't for the pullbar as it doens't have enought angle in the LR swing arm to climb the bars just by the excelleration forces alone, it needs the extra force from the pullbar to make this happen consistantly. If you are using a swing arm or 2 link type set up you need a pullbar but on a 4-link (much steeper angles) you (my opinion) would be better off with a torque arm and on the hook. I do believe the reason alot of MOD are clamped in front instead of on the hook is because of the pull bar.

These are my opinions and should be taken as such OPINIONS!

[profab00]

Hey-hey! Thanks for getting me off the hook. I thought all day about how to post an answer without posting over the internet my set-up.....which I will not. Shocks, your numbers aren't that far off. You got to think like you are setting up a late model and not a mod when you use a torque arm. Meaning, you was probably off in other areas......like wedge? I agree on a pull bar with Billet which is why I build my own chassis, but still, on the super dry slick like a daytime event where the track goes to powder.....I haven't found the right combo yet. But overall, I don't lack for forward bite. In fact, my rf shock takes forward bite out....like some late models.

[mbaker76]

what do you mean Rf shock takes forward bite out? ARe you talking like an easy down or tie down shockon the RF?

Years ago we had a car that had a lift arm in it, but it was swingarm zlink both sides. I know it wasnt a great combintaion but we were just getting started and we didnt know any better. Anyway I cant remember how everything was fitted or whether it had a chain or anything. I know it had a slider with the 5th coil (cant remember rate either) and then the shock. Not sure if there was a chain for the brake side or if the shock was the stop.

Couple years ago we ran a brake chain on the arm with a pullbar in our 4bar mod. I didnt like having the chain slam tight on braking and was going to try and put the damper shock on the arm and do away with the 90/10 but there wasnt enough travel to make that work. We have all the pieces and I still think about doing it but cant find much info on it, nobody i know of has even tried it to ask about it so any help would be great. In my mind I knew what shock and spring i wanted to try on the 5th coil but never did figure out what to do with the brake/6th coil side, or how long to make the arm.

[profab00]

Exactly, the rf has a stiffer rebound than the compression.

[billetbirdcage]

what do you mean Rf shock takes forward bite out? ARe you talking like an easy down or tie down shockon the RF?

Years ago we had a car that had a lift arm in it, but it was swingarm zlink both sides. I know it wasnt a great combintaion but we were just getting started and we didnt know any better. Anyway I cant remember how everything was fitted or whether it had a chain or anything. I know it had a slider with the 5th coil (cant remember rate either) and then the shock. Not sure if there was a chain for the brake side or if the shock was the stop.

Couple years ago we ran a brake chain on the arm with a pullbar in our 4bar mod. I didnt like having the chain slam tight on braking and was going to try and put the damper shock on the arm and do away with the 90/10 but there wasnt enough travel to make that work. We have all the pieces and I still think about doing it but cant find much info on it, nobody i know of has even tried it to ask about it so any help would be great. In my mind I knew what shock and spring i wanted to try on the 5th coil but never did figure out what to do with the brake/6th coil side, or how long to make the arm.



If you brakes are attached to the axle tube you need some sort of dampner on the torque arm (I.E. a 6th coil or some sort of rubber bushing). If your brakes are floated on the cages or seperate floater then you can get away with a solid chain.

I have went as far as using a pullbar and a 5th coil at the same time. I used the rate of the 5th arm to control when it transitioned between the two. Some guys have used a stiff 5th coil and left it with a fair amount of slop so it used the pullbar for the first couple of inches and then split the force between the two. I had fair success with it, but was playing with it when we first got on the hook so we all had several other things to figure out at the same time. I just never went back to it to sort it out later on.

If you really want to get trick. Talk to some polevault manufacturers about their products, I know they could make me anything I wanted. You would use that for a torque arm with no spring as the arm itself would be the spring (similar to a rease bar). You would conform to the rules by not having extra springs and would have plenty of room. I had this all figured out at one point (for a LM) except the rate would be a trail and error deal, as they can make the poles progressive or degressive and in about any rate.

[Timmay]

My opinion is THERE IS NO PERFECT SET UP. You can get anything to work if you take time to understand it. I have seen the stupidest setups go out and mop A$$.

My brother had a 4-bar mod a few years back that had a 5th arm with a solid chain. He ran no shocks on the 5th-arm, just a spring on a coil slider. Then he ran a 90/10 on top of the axle. He floated the RR spring and clamped the LR spring. That car ran like a striped-A$$ Ape (tacky or dry), and won a lot of races.

Forget all the trick stuff, and stick with a basic setup. 5th arms work, and so do pull bars. I would choose whatever gets you on the track with the least time & money.

[shocks]

We bought a reese bar back when we were doing the 5th arm testing, but never got around to trying out the reese bar.

I did not mean that literally, only one person would have the lift bar thing working, probably should have clarified that more. My bad there. My point was simply that for most people a pullbar setup is going to get them into the ballpark quicker as it is the more common way of doing things and has less "mystery" to it's setup and how it works on a mod than does a lift bar. I still feel that way.

Anyhow, my apologies for my opinions being taken wrong. I obviously didn't word things clearly enough as several people seem to have taken what I said differently than intended.

--shocks

I think the major thing that is going to make this difficult is the large diameter springs you have to use. This will likely make the 5th coil need to be too far to the right of the driveshaft (just for clearance) and will likely cause the RF to slide under throttle.

My personal opinion is a 2 way pullbar has NO place on any racecar but an asphalt car. Anytime the brake and decell forces are transfered thru the pulbar (downward angle to the frame) it will try to lift the rear end and make the car looser on entry. If that is a common problem for you then one may help. The car would be more consistant without it because you always don't or can't use the same amount of engine or brake braking throughout the race (lap traffic or whatnot). With a torque arm and a bushing/spring to control the engine decell or barke forces the car will be tighter on entry and more constistant over the different stages of a race (leading, following, or lapping cars).

Second thing is a torque arm (for the most part) is lifting on the chassis and not transferring forces to the rear end that is pushing forward or backwards on the rear end, like a pull bar does. A pull bar is pulling on the devise but because it is running forward it also tries to shove the rearend forward as the pullbar get flatter. That force is very strong, so you now have alot more force on the 4-link bars then a torque arm will. This make it alot easier to climb the bars and is most of the reseason you see less bar angle ran on a car will a pull bar car then a toque arm car. A rayburn would likely not hike up if it wasn't for the pullbar as it doens't have enought angle in the LR swing arm to climb the bars just by the excelleration forces alone, it needs the extra force from the pullbar to make this happen consistantly. If you are using a swing arm or 2 link type set up you need a pullbar but on a 4-link (much steeper angles) you (my opinion) would be better off with a torque arm and on the hook. I do believe the reason alot of MOD are clamped in front instead of on the hook is because of the pull bar.

These are my opinions and should be taken as such OPINIONS!

[mbaker76]

here is a question, driver has said our car with pullbar is really good but there are times on a spotty track where you could be going along floorboard deep come off the corner hit a slick spot and buzz the tires. I told him i didnt know if there was much we could do about that other than foot control. Would a torque arm help with that problem?

The last few years we have been taking angle out of the pullbars, from 18-20 on our 2 link cars down to about 12 on the 4 link cars and car seems to work better. I was doing it thinking that i didnt want the pullbar lifting as much to provide traction i wanted the trailing arms to do that. But now it seems like i may have been going at it backwards, i took all the lift away that the pullbar would add traction with and now it is simply 'pulling' forward getting or keeping the car on the bars. maybe we are missing out on some added traction especially in the middle of the corner by doing that. Maybe thats why it seems like we run a little more bar angle than others, they are running more pullbar angle and that helps them in the middle.

If you were going to run a lift arm on a mod, what length? since the wheelbase is longer should the arm be longer or would it be ok since a mod with more rear % would have teh CG furthur back?

[race81]

mcbaker i dont think thats unusual coming from a drivers standpoint, id buzz my tires off at a high momentum track if i hit dust or a small dip. horsepower to tire size is getting crazy in our classes. billet said our large 5th arm springs could be a downfall, but what is our option now that imca and others are now allowing coil overs? on the rear that is. another question is late models w/5th arm clamping both sides? floating?

[mbaker76]

Here is what im thinking now, see what you guys think and agree/disagree. 4/4 car floated both sides, 350#? 5th coil on coil0ver with 3-7 shock at 32-36" then some sort of rubber bushing in place of a 6th coil unit. How far away should the 6th coil be or does it make that much difference?

[race81]

doesnt sound bad, but being floated on both sides would a fifth arm be enough to get you up on the bars? i dont get the whole 6th arm thing, is it used to take the place of a 90-10 shock? decisions.....decisions, makes you wish you had a track to experiment at all year doesnt it!

[mbaker76]

Thats what I dont know. With a late model it will but its alot more tire. Maybe with a mod you would need more spring to help get the car up on the bars, maybe not.

I hear you on the practice sessions. The problem i am going to have is convincing the driver to take a top5 car and play around with this, even if its just for heat races or something. Thats why if i do it I need to have it close right off the bat to keep him interested. Would be nice to hear from anybody that is making it work.

[race81]

my first mod was a mono-leaf, sliders w/175 springs, 2-link, 5th arm was mounted solid to the axle(no heims) had a 250-275 spring on it with a 90-10 shock. it had no problem with bite going forword, but with mono-leafs i found them to be a little less than consistant. so we scrapped that car. this setup has to be used somewhere. dont blame your driver, id be a little hesitant to make big changes to a top 5 car also. drivers have this thing about the possabiliity of (looking bad on the track) I call it fear!! lol..

[mbaker76]

I dont blame him, its sometimes tough for me to convince myself to try something different as well. But there were many times this year we took chances that paid off and we learned a lot that in years past we maybe wouldnt have done for fear of going backwards. A good personal practice track would be nice......

[billetbirdcage]

We bought a reese bar back when we were doing the 5th arm testing, but never got around to trying out the reese bar.

I did not mean that literally, only one person would have the lift bar thing working, probably should have clarified that more. My bad there. My point was simply that for most people a pullbar setup is going to get them into the ballpark quicker as it is the more common way of doing things and has less "mystery" to it's setup and how it works on a mod than does a lift bar. I still feel that way.

Anyhow, my apologies for my opinions being taken wrong. I obviously didn't word things clearly enough as several people seem to have taken what I said differently than intended.

--shocks


If that was directed to me, I didn't think you meant anything by it. (no harm no foul). I was just stating that I also knew someone that has made it work, so that makes two people for sure. So I'd think there are many more out there somewhere that has done the same.

I would also agree that the pullbar is so common that if you use a torque arm instead you are going to be on your own for the most part and likely struggle for a while before you get better. You may also get worse and never get back to the speed you were before or just end up at the same speed but spent alot of time and money for nothing.

[billetbirdcage]

here is a question, driver has said our car with pullbar is really good but there are times on a spotty track where you could be going along floorboard deep come off the corner hit a slick spot and buzz the tires. I told him i didnt know if there was much we could do about that other than foot control. Would a torque arm help with that problem?

I have very limited MOD experience but I would think you would have this problem with either set-up. although you have alot more pinion movement with a pullbar and therefore the pinion side of the panhard bar is going to move more up and down changing the rake more then a torque arm should. How much is that going to effect the car, hard to say.

The last few years we have been taking angle out of the pullbars, from 18-20 on our 2 link cars down to about 12 on the 4 link cars and car seems to work better. I was doing it thinking that i didnt want the pullbar lifting as much to provide traction i wanted the trailing arms to do that. But now it seems like i may have been going at it backwards, i took all the lift away that the pullbar would add traction with and now it is simply 'pulling' forward getting or keeping the car on the bars. maybe we are missing out on some added traction especially in the middle of the corner by doing that. Maybe thats why it seems like we run a little more bar angle than others, they are running more pullbar angle and that helps them in the middle.

What I see is, theoritially the flatter the pullbar is the more bar angle you will generally run. Also the shorter the pullbar is the quicker it will flatten out which could also come into play.

If you were going to run a lift arm on a mod, what length? since the wheelbase is longer should the arm be longer or would it be ok since a mod with more rear % would have teh CG furthur back?

This is a complete guess! I'd be tempted to mount the torque arm closer to the middle of the pumpkin instead of the right side of the pumpkin. As Profab hinted at (maybe that was a hint) with the torque arm mounted like a LM (to the right of the pumpkin) you will likely need more LR bite as it will not favor the LR tire as much as a pullbar mounted in the middle.

A complete guess?

[race81]

mbaker, looking around and found www.hassychassis.com, they have some good pictures of a setup simular to what your thinking about. just thoght id let you know....

[mbaker76]

race81
thanks for the link.

Billet,
Can you see any advantage to running less pullbar angle. Maybe there isnt an advantage one way or the other, just finding the right combination. One thing we used to fight was brake chatter, since we started taking angle out that went away so maybe that is one plus. The other thing i can see is that less pullbar angle would affect the car less on entry I would think? More angle would tend to loosen the car right?

Your right our lift arm mounts are to the right in order to clear the jbar mount, so there really isnt any way to move them furthur left. So compared to the pullbar which we run at the pinion or just left of pinion the torque arm would be acting at a point almost 6-8" to the right of the pinion. That 8-9" would prob make some difference in loading huh? Are late model rearends offset to the left to counter that effect?

The other thing is when we took angle out we lowered the bar on the rearend. We dont have anymore holes to raise on the frame unless we make something up to do it. But maybe that would be better, keep the same angle and move the whole bar up. I remember seeing somewhere where if you took like a 2 link car and looking at the side of it found the intersection between the lower link and the third link extended forward that was your lift point as if it were a lift arm. Any truth to that? If there is then when we go 4 bar and find the thrust line of the bars and the intersection of the pullbar it gives a effective ift arm length(depending on bar angle) of like 24" vs 33-36 i see in late model sheets. Maybe raising the whole bar would move the lift point furthur forward closer to the 33-36 range. Anything to that line of that? good bad otherwise?

[profab00]

Maybe I am out in left field on some my theories as to why....but here goes. A lift arm takes weight off the right front. My car has to on the right front to be really quick. Billett is right on his guess of wedge and where my torque arm is mounted. MBaker, that spring would be too much spring (torque arm spring) for my chassis. Try a 275 instead. The heavier hooks up harder at times but then the old dreaded middle of the straight comes up, it breaks traction. One last comment, the four bar four bar chassis, I couldn't keep the car down on the right rear. When I gave it gas, it got up on the bars on both sides. The right rear, in my opinion, needs to be down digging on a mod, not up. Careful springing this deal on the left rear also.....don't spring it like you are talking unless your track is really hooked up.

[shocks]

I would also agree that the pullbar is so common that if you use a torque arm instead you are going to be on your own for the most part and likely struggle for a while before you get better. You may also get worse and never get back to the speed you were before or just end up at the same speed but spent alot of time and money for nothing.

That's pretty much why we went back to the pullbar. The torque arm setup was coming around, but for the chassis we use, we didn't foresee it developing into anything any better than our pullbar setup. There simply came a time when we felt that it was in the best interest of our finances to go back to what we knew how to work with.

Once "play-days" start next season i'll throw the torque arm back on and try it out some more. If we can get it to work, and be faster than we are with the pullbar, i'll be the first to admit that I didn't give the setup enough of a chance or enough experimentation time the first go around to make a good evaluation of it's potential.

Again, I'd like to be able to get it to work as I think a person could definitely make the car better on entry with the torque arm than with a two way pullbar. Just gotta convince myself that we can get the drive out of the corners with it.

--shocks

[billetbirdcage]

Billet,
Can you see any advantage to running less pullbar angle. Maybe there isnt an advantage one way or the other, just finding the right combination.

Both probably have their advantages and disadvantages, combo would have more to do with it then anything.

One thing we used to fight was brake chatter, since we started taking angle out that went away so maybe that is one plus. The other thing i can see is that less pullbar angle would affect the car less on entry I would think? More angle would tend to loosen the car right?

I don't have a problem with a pullbar, just a 2 way pull bar. I wouldn't want the engine decell forces going thru the pullbar (downward angle to frame) as it unloads the rear tires and makes hike down problems worse. If you are using one of these the less angle is the lesser of the two evils in MY EYES, but I'm also not a MOD guy. If rules allow I'd use a torque arm for braking purpose and remove any biskits or travel limitations on the pullbar so the pullbar doesn't push on frame during decell (just slides together). Use some sort of spring or bushing (or what not depending on your rules) for a dampner on the chain. This will be tighter on entry and likely more consistant and eliminate wheel hop or brake chatter.

Your right our lift arm mounts are to the right in order to clear the jbar mount, so there really isnt any way to move them furthur left. So compared to the pullbar which we run at the pinion or just left of pinion the torque arm would be acting at a point almost 6-8" to the right of the pinion. That 8-9" would prob make some difference in loading huh? Are late model rearends offset to the left to counter that effect?

You can put it anywhere you want if you will work at it. I have seen them ran on the left side of the centersection on a LM before. You will just have to build one yourself and add extra bracing because it will need to curve under the driveshaft and back over to the right side of the driveshaft. Not that difficult just takes so time to sort out any cleareance issues that may come up.

A LM has typically either a 33/36 rear end or a 34/35 rear end (tubes), so the pumpkin or center section is offset to the left a small amont but sine the torque arms is mounted to the right side of the centersection it is still closer to the RR tire then the LR tire by a inch or two.

The other thing is when we took angle out we lowered the bar on the rearend. We dont have anymore holes to raise on the frame unless we make something up to do it. But maybe that would be better, keep the same angle and move the whole bar up. I remember seeing somewhere where if you took like a 2 link car and looking at the side of it found the intersection between the lower link and the third link extended forward that was your lift point as if it were a lift arm. Any truth to that? If there is then when we go 4 bar and find the thrust line of the bars and the intersection of the pullbar it gives a effective ift arm length(depending on bar angle) of like 24" vs 33-36 i see in late model sheets. Maybe raising the whole bar would move the lift point furthur forward closer to the 33-36 range. Anything to that line of that? good bad otherwise?

Your changing the leverage point of the rear end by moving it up and effectively stiffening the rate by moving it up. Yes it is similar and you can figure it that way, look for some drag racing sites on google or somewhere and you'll should be able to find something that should explain that. It will show the instant center of the rear suspension.

[Timmay]

2-way pullbars work fine on mods. ( as long as you run a 90/10 on top of the axle) You can try to run a ladder bar to take braking, but I think it's unnecessary. Both devices will try to squat the rearend under decel. The more angle in the pullbar, the more it will want to squat. The shorter your 5th arm (or ladder bar) is the more it will squat. I don't think any advantage that running both devices would be worth the additional unsprung weight.

Most mods around my neck of the woods run 2-way pullbars quite successfully. I'm not bad-mouthing 5th arms, because if I already had a car with a 5th arm, I would just tune it to work. If I was building a car from scratch I would probably just use a 2-way pullbar, especially if it was a 2/3-link, swingarm, z-link, or a 4/Z combo. If it was 4-bar both sides, I could go either way, pullbar or 5th arm.

Have fun!

[Timmay]

By the way, when we were pretty successful with the 5th arm on mods we ran:
*solid brake chain out at 40"
*250 to 300lb springs out at 36" with additional mounting holes at 34" and 32".
* no shock on 5th arm
* 90/10 on top of axle

[mbaker76]

BBC,
I guess im am confused as to why a 2 way bar would be worse than a straight pull bar. I understand why it would be unloading the rear under braking, but in my mind a straight 1 way pull bar is going to unload the rear more on the brakes because there is no give on the braking side, whereas with a 2 way bar will give more on the brakes and absorb some more of the braking force before unloading the rear.

I guess maybe it comes down to what you are considering a 2 way bar, I guess technically pretty much all of them are 2 way, because any of them i have seen have at least a rubber bushing on the brake side. It may not give much if any at all so to me i think of that as a 1 way bar vs. the newer AFCO 2 way or BSB or some of those.

I also like the idea of the chain with damper for the brake arm, then leaving the brake side of the pullbar open. I guess you would just leave the preload nut off the front and set preload with the chain? And by using a rubber pull spring, you could put an actual coil spring on the chain and still be within the spring rules, granted it would have to be a 5 "spring but it could be done.

[billetbirdcage]

My statements probably were confusing.

As Timmay pointed out on the two-way with the 90/10 shock.

I'll try this again (I was jumping around).

A straight pullbar (pushes together without transfering braking or decell forces thru the frame) has to have something that stops the downward pinion travel. If this is a 90/10 with a bumper on it and it is mounts level or uphill to the frame, the decell and braking force goes thru this. It will use the shock valving to push downward on the rearend (very temperary but there) and then hits the bumper on the shaft of the shock and pushes thru the shock. If that shock is level or uphill it doesn't try to lift the rear end.

So with this you have to use a 90/10 with some sort of stop (bumper or bottoming out the shock) or use a torque arm with a chain to control these forces. Either way will lift the rearend less then a 2-way pullbar by itself (no 90/10). The torque arm with still lift the rear end but not to the degree of a 2-way with downward angle to the frame will.

With the torque arm you can move the 6th coil forward or back (not common to do this once you fine the right place) to control where it is pulling down on the front end of the car. Using some trail braking or just brakes can make the car pull the front end down and try to help the RF stick or help it turn. There are other thing that this can allow you to do in the cockpit to change the handling of the car. That is why if you don't want to spend the time and money to try a torque arm for the tracion part and what to stay with the tried and true pullbar, I'd use a torque arm for the braking and decell forces. To me it is just more constistant and allow the driver to adapt the car more then other wise.

Like I said this is based of a few guys and manufacturers I help some and opinion. So don't take this as fact, just what I beleive and have seen thru my limited exposure to MODS.

[mbaker76]

thanks Billet that makes sense now, and the more I think about it it gets clearer. I remember hearing somewhere about some cars that you unhooked the pullbar to scale it and set pinion angle with the bumpers on the 90/10, just never thought about it much. I do like the idea though, may have to think about it some more. Would let you keep the pullbar on the left side for bite, and yet get the braking benefits of the torque arm without a lot of work. Maybe be able to get that part of it tuned in then possibly go to a 5th coil setup later. How far is the 6th coil from the rearend, typically? If we are talking 5th coil at 32-36 i assume 6th coil would be around 40-42? Or would it depend on wheelbase, since the mod wheelbase is longer?

[mbaker76]

Billet,

I know somewhere you mentioned you thought a torque arm on a mod might make it push because it would take too much weight off the RF. Do you think a mod could get away with less rear % then, putting more static weight bias on the front which would help the car turn in, then when on the gas the rear would get loaded but still have enough on the front to steer? OR maybe a shorter lift arm (26-30" range), to get more initial traction like a pullbar would.

Maybe thats part of why a pullbar works good on a mod, typically the rear % is higher and at least in my layouts the effective lift point is closer to the rear, so it wouldnt be lifting the RF as much. At the same time the pullbar is lifting more under the center of mass of a high rear% car, wheras the liftarm is likely forward of the center of mass. Therefor the pullbar is trying to lift the entire mass but since its closer to the rear it doesnt affect the front as much, but a liftarm would be lifting forward of the center of mass and would unload the front more, adding to the already heavy rear and overloading the rear with traction.

Kind of a which came first sort of deal, maybe since the cars were typically rear heavy drivers would try a lift arm and it doenst work but a pullbar does, and thus mods have kind of gotten stuck with a pullbar. On the other hand if they would have started with lift arm and low rear% numbers then try to go to a pullbar it wouldnt work either.

[KTM-Lew]

Seems like these guys would be the ones to talk too?

http://www.hassychassis.com/cardevelopment.html

[billetbirdcage]

thanks Billet that makes sense now, and the more I think about it it gets clearer. I remember hearing somewhere about some cars that you unhooked the pullbar to scale it and set pinion angle with the bumpers on the 90/10, just never thought about it much. I do like the idea though, may have to think about it some more. Would let you keep the pullbar on the left side for bite, and yet get the braking benefits of the torque arm without a lot of work. Maybe be able to get that part of it tuned in then possibly go to a 5th coil setup later. How far is the 6th coil from the rearend, typically? If we are talking 5th coil at 32-36 i assume 6th coil would be around 40-42? Or would it depend on wheelbase, since the mod wheelbase is longer?

At the end of the torque arm will generally put the 6th coil about that 40 to 42" with a torque arm that can adjust from 32" to 38". I can't tell you if that would be right for a MOD, but from what others have said that seems on a MOD so that sould be close to start.

Even thought the wheel base may be longer the higher rear wieght of a MOD should move the COG back in the car and therefore probably don't need as long of a torque arm. So with the longer wheel base but the COG farther back should be about a wash and be close to a LM, I would guess.

[billetbirdcage]

Billet,

I know somewhere you mentioned you thought a torque arm on a mod might make it push because it would take too much weight off the RF. Do you think a mod could get away with less rear % then, putting more static weight bias on the front which would help the car turn in, then when on the gas the rear would get loaded but still have enough on the front to steer? OR maybe a shorter lift arm (26-30" range), to get more initial traction like a pullbar would.

Maybe thats part of why a pullbar works good on a mod, typically the rear % is higher and at least in my layouts the effective lift point is closer to the rear, so it wouldnt be lifting the RF as much. At the same time the pullbar is lifting more under the center of mass of a high rear% car, wheras the liftarm is likely forward of the center of mass. Therefor the pullbar is trying to lift the entire mass but since its closer to the rear it doesnt affect the front as much, but a liftarm would be lifting forward of the center of mass and would unload the front more, adding to the already heavy rear and overloading the rear with traction.

Kind of a which came first sort of deal, maybe since the cars were typically rear heavy drivers would try a lift arm and it doenst work but a pullbar does, and thus mods have kind of gotten stuck with a pullbar. On the other hand if they would have started with lift arm and low rear% numbers then try to go to a pullbar it wouldnt work either.


I was refering to that fact that a torque arm with a fifth coil is going to be lifting on the chassis to the right of the driveshaft by a couple of inches (minimun to clear the shaft) where a pullbar is usually mounted inline with the drive shaft. Depending on the offset of the car the pullbar is likely to the left of the center of the car and the torque arm is farther to the right. Just means it is lifting on the chassis closer to the RF tire then the pullbar would or should be.

If you hooked any traction devise to the right frame rail, it will likely slide the RF tire during throttle, I was just pointing out that this could or may happen since a 5th coil on the torque arm would likely be mounted closer the the right side of the car then a typical pullbar set-up. It may cause problems it may not, I'm guessing at this point.

[billetbirdcage]

I just feel it is better to seperate the two forces. Acceleration and Decelleration/braking forces. With a pullbar for Accel, I would use a 90/10 with a bumper or a torque arm. This will help seperate those forces and allow you to adjust one of those items without heavily effecting the other. If you added angle to a 2way pullbar (nothing else to control decel/braking) you will loosen the car on entry or flattening it out will tighten entry. Of course this is going to depend on car attitude and drive to how much if any effect will be had. If you have something else controling decel/braking (I.E. 90/10 w/ bumper or torque arm and chain) you can make a change without effecting the other.

If you wanted to loosen entry you could subtract angle to the 90/10 or stiffen the 6th coil on the torque arm. I just allows for better and finer adjustments without effecting other things you may not want to.

With a 2 way you can't really seperate those forces except the rates on the springs or bushings but can't adjust the angle without effect the other part of the corner.


Edit said backwards

[Rocket Bonehead]

Yee-haw... I hadn't checked out the Mod forum before this, but it definitely looks as if things are hot and heavy in this topic, lol...


I too am not as up to speed on mods as I'd like, simply because I don't get to work hands on with them, but I do feel that many of the same things would still apply (between the two types of cars). I'd kill to get my hands on one of those Hassey cars... I doubt you could get a modified any closer to a Rocket than their cars, unless you converted a Rocket DLM to a modified...


I have had a number of guys contact me for help with their mods. Most are on a pull-bar, but I've got a couple using lift-arms. I tend to agree with Billet that I think a lift arm will work just fine once you get the right length/spring combo figured out for that particular car. Without giving away their setups, the guys I've helped that are using a lift arm are running anywhere from a 250 to 300 between 36" and 32" out. It does seem like their cars work better with the lift arm farther back. I'd have to dig deep thru my emails to find out whether they were using a 6th coil or a just a chain as I don't remember off the top of my head.



RB

[fourbar83]

... I doubt you could get a modified any closer to a Rocket than their cars, unless you converted a Rocket DLM to a modified...RB

A Throw-N-Dirt Chassis is a Rocket Chassis with a Metric front clip.

[race81]

bbc, do you know the correct position left to right for a pullbar or liftbar? if it was possible to mount left of the pinion would it be better, or is a more centered position desired. i myself build my own chassis and im new at it, i believe my center of gravity is alot more left than most chassis. would it be plausible to offset engine, trans and driveshaft to mount a liftbar to the left? and i know this is way out there, but so were lots of ideas now used as the normal years ago................ thanx.

[Timmay]

I ain't BBC, but I'll tell you this.

On a mod, you want to get the 5th arm as close to the drive shaft as you can comfortably get. You also want to side brace the 5th arm to the chassis. If you want a lift bar that's left of the driveshaft, you need to start looking at a reese bar.

If you run a "single pull" pullbar with a braking ladderbar, you want to keep the ladder bar shorter than a regular 5th arm. The reason for this, is that a pullbar wraps up a lot more than a 5th arm would, and if the ladder bar is too long you might start hitting your 6th spring mounts or other parts of the chassis if you're not carefull. I would also suggest side bracing the ladderbar back to the axle housing (not the chassis), because the extra wrap up of the pull bar will start to exceed the upward travel capability of the chassis side brace, and can start lifting the chassis through this side brace.

[race81]

timmay could you explain a reese bar to me, ive never heard of one. also has anyone ever mounted a liftbar directly over the driveshaft, or would it be impossible to brace the rear axle for such a thing.

[Timmay]

Reese bars are way before my time. I think that they were used a lot more back in the 80's. I have, recently, seen some on modifieds, and work quite well. What I do know about them is that the are just a solid bar that's mounted underneath the axle tube. They use some type of collar on the chassis, where they are free to slide in and out of. They come in different rates. They are basically a trailer hitch bar. The couple of mods that I've seen with reese bars, were running them to the left of the chassis, running underneath the cockpit. Maybe some of the old-schoolers on here can shed some more light than I can.

I also remember seeing pictures somewhere of a funky 80's latemodel setup with 2 fiberglass torque-arms mounted on each side of the drive shaft.

If it were me, I'd stick to a 5th arm to the right of the drive shaft, or a pull bar I could put anywhere I want.

Good Luck!

[profab00]

If you brace over to the frame on a torque arm, one needs to heim joint the ends of the torque arm to allow the torque arm movement as the j-bar is working without binding.

[billetbirdcage]

bbc, do you know the correct position left to right for a pullbar or liftbar? if it was possible to mount left of the pinion would it be better, or is a more centered position desired. i myself build my own chassis and im new at it, i believe my center of gravity is alot more left than most chassis. would it be plausible to offset engine, trans and driveshaft to mount a liftbar to the left? and i know this is way out there, but so were lots of ideas now used as the normal years ago................ thanx.

There is no set position for a torque arm or pullbar persay. If it is dead center between the two rear tires it will bias both tires evenly. If it is move left or right it will bais that tire more then the other. If you move it right (rear end only- NOT talking frame) it will bias the RR tire more then the left and should drive the car round the corner (loosening exit), if you move it left it will tighten the exit by biasing the LR tire more then the RR.

Where it mounts on the rear end and where it is pushing on the frame (top of fifth coil) are to seperate items. Mounting point on rear end is bias at rear tires and mounting of the top of the fifth coil is where it lifts on frame (forward, back, left or right).

You could offset everything, but you are going to add Left side wieght also. You can attach the torque arm to the left of the pinion (or anywhere you want) but will likely have to jog the torque arm back over the the right side of the drive shaft to have room of a fifth coil. You CAN do this it just takes some work to get it built right and still be strong so it doesn't break. This is much more plausible if you trying to get more dymanic LR bite upon throttle up, then moving everything to the left and having to start all over as you are changing numberous items that are going to effect the car.

A reese bar is a flat tapered looking piece of spring steel that attaches to the rearend and then goes into a mount on the frame (usually lined with rubber- basically a round hole lined with rubber). it is similar to using the main leaf out of a leaf spring and using it for a torque arm. The arm itself is the spring, so it can be mounted more easily as it doesn't use a fifth coil. They were most commonly used on the Left side of the driveshaft (as Timmay said) and the fornt end mounted on the left side of the driveshaft close to the shifters. The front mount just needs to let the reese bar slide front to back as to not bind up the suspension as the rearend moves forward or backwards.

Read my post about the polevault deal, I was talking about using this in place of a reese bar. Much lighter and they can make any rate you want.

Also if you decide to go the torque arm (for traction, not just braking with the pullbar for traction) you will likely need to run the hook instead of the clamped LR in front. You will lose a fair amount of upward pinion movement with the torque arm and therefore lose some of the effect of the clamp bracker indexing up inot the LR spring upon throttle up. In my eyes to use a torque arm you need to be on the hook as I don't think it will work as will if the spring is clamped on the LR in front.

Again opinions NO testing and limited MOD experience.

[billetbirdcage]

I also remember seeing pictures somewhere of a funky 80's latemodel setup with 2 fiberglass torque-arms mounted on each side of the drive shaft.

Good Luck!

Never saw the 2 set up , but I have used the single one on a LM before. I don't think you can still buy them though. They will scare the H$ll out of you if you saw how far they bowe under throttle. They did have a tendency to break after the aged some though, seemed to work fairly well.

[KTM-Lew]

Never saw the 2 set up , but I have used the single one on a LM before. I don't think you can still buy them though. They will scare the H$ll out of you if you saw how far they bowe under throttle. They did have a tendency to break after the aged some though, seemed to work fairly well.

Looks like Flex-i-flyer still makes them?

http://flex-a-form.com/products.asp

[billetbirdcage]

Yep, thats it. It even shows the mount for a Q/C. I didn't think anyone still made them, I guessed wrong.

[Timmay]

Also if you decide to go the torque arm (for traction, not just braking with the pullbar for traction) you will likely need to run the hook instead of the clamped LR in front. You will lose a fair amount of upward pinion movement with the torque arm and therefore lose some of the effect of the clamp bracker indexing up inot the LR spring upon throttle up. In my eyes to use a torque arm you need to be on the hook as I don't think it will work as will if the spring is clamped on the LR in front.

Again opinions NO testing and limited MOD experience.

Billet,

Actually, one of the fastest mods my brother had was a 4bar/clamped LR/5th arm. We thought the 5th arm worked great with the clamped LR, and the 5th arm seemed to key to tuning the car in. He would do most of the tuning of the car with the 5th arm spring and wedge adjustments. If he needed more forward bite, he would soften up the spring to allow more pinion wrap up. More pinion wrap-up on a clamped LR means more LR drive. He stiffened it up for tacky tracks to minimize pinion wrap up to free the car up. I had a similar car, and I can agree that softening or stiffening the 5th arms spring made a real difference on a clamped car. Conversely, I can't feel hardly any difference when changing the 5th-arm spring rate on a fully floated car. If anything forward bite may actually get a little worse by going softer on the 5th arm for a full-floated car.

[mbaker76]

timmay,

So you have run a 4/4 floated mod a liftarm? what about pllbar? How did the 2 compare?

Any hints you would like to give out for a floated setup W/ liftarm?

You mentioned that softening the spring on a clamped car would allow more pinion wrap and more LR bite. I have thought all along that maybe that is why mods a long time ago 'generally' got stuck with a pullbar. They wanted the pinion wrap to load the LR under acceleration but when you go softer on the 5th coil you might (just guessing) lose some of the initial bite that you can gain back with the pullbar vs. liftarm, plus like you say you get a lot more movement at the end of a 36" arm and could have that thing whipping all over the place. Now on a floated car you dont really need or want a lot ot pinion wrap and even with our pullbar car we are keeping travel at roughly 1" which at the end of the arm would be around 3", seems typical i guess.

[race81]

any of you guys know of a company that offers a coil over dummyshock to mount a small spring for a lift bar like late model guys use. something thats not to over priced.

[mbaker76]

just use a slider

[race81]

yep,your right it would be cheaper, i always had problems with them binding in years past though.

[Timmay]

timmay,

So you have run a 4/4 floated mod a liftarm? what about pllbar? How did the 2 compare?

Any hints you would like to give out for a floated setup W/ liftarm?

You mentioned that softening the spring on a clamped car would allow more pinion wrap and more LR bite. I have thought all along that maybe that is why mods a long time ago 'generally' got stuck with a pullbar. They wanted the pinion wrap to load the LR under acceleration but when you go softer on the 5th coil you might (just guessing) lose some of the initial bite that you can gain back with the pullbar vs. liftarm, plus like you say you get a lot more movement at the end of a 36" arm and could have that thing whipping all over the place. Now on a floated car you dont really need or want a lot ot pinion wrap and even with our pullbar car we are keeping travel at roughly 1" which at the end of the arm would be around 3", seems typical i guess.

mbaker, I have no car now, I'm more or less semi-retired, until my kids are old enough to get in the pits and turn wrenches. (and to take over my household chores) :-D

When we worked with full-floated 4/4 car with 5th arms, we used similar set-ups to late models for the rear suspension, but we used a little softer springs, a little more angle on the LR bars, and a little less angle on the RR bars. We didn't run a huge amount of rake on the j-bar (4 to 5 inches). You basically had to rely on the bar angles to get the bite in the car. This setup was as fast as anything if you nailed the setup. You had to chase the set up a little bit with the LR bars and LR spring when track conditions changed, or when you ran at different tracks.

We had more success with the LR clamped up. The clamped up deal was always more consistent and a lot easier to tune. We rarely had to play with the springs and bar angles. You could also take it to different tracks and always be in the ballpark right off the trailer.

When we played with a pullbar with the 4-bar setup, you had to limit how much angle you had in the pullbar and the angle in the LR bars. Too much angle in either would make the car erratic. You can get it to work, just watch your angles. If you float the LR behind, don't get too soft on the LR spring.

How are you keeping your pullbar to only 1" of travel? Is it a 3 link or a 4-link? Is it a biscuit bar or a spring bar? Do you have to preload it a lot?

[mbaker76]

its 4/4 floated, biscuit bar by Coleman with 'aircraft' rubber biscuits. get about 1 to 1 1/4 on the pull side and 1/2-3/4 on the brake side. no preload really, just enough to keep everything snug. not much angle either, maybe 12-14* on the pullbar.

[race81]

Is There Any Advantage Or Disadvantage To Mounting A 90-10 Over The Rear Axle Or Mounting It On Front Af A Liftbar?

[mbaker76]

you dont want to run an actual 90/10 on the end of a torque arm, its the wrong valving it is an easy out hard in, on the torque arm you want easy in hard out, like a 3-6 or 3-7.

If you generically mean 90/10 as a damper shock then i can see advantages both ways, but im still thinking, in general i think the 90/10 on top the housing tends to hurt sidebite because it kind of binds the car up not letting it roll as easy. You also run the risk of topping it out on acceleration if you get lots of pulbar travel and LR movmement. This can lmit pullbar movement and effectively make it a solid bar, but i think it can break the tires loose when it hits the top of the shock as there is no cushion left in the pullbar.

[billetbirdcage]

Billet,

Actually, one of the fastest mods my brother had was a 4bar/clamped LR/5th arm. We thought the 5th arm worked great with the clamped LR, and the 5th arm seemed to key to tuning the car in. He would do most of the tuning of the car with the 5th arm spring and wedge adjustments. If he needed more forward bite, he would soften up the spring to allow more pinion wrap up. More pinion wrap-up on a clamped LR means more LR drive. He stiffened it up for tacky tracks to minimize pinion wrap up to free the car up. I had a similar car, and I can agree that softening or stiffening the 5th arms spring made a real difference on a clamped car. Conversely, I can't feel hardly any difference when changing the 5th-arm spring rate on a fully floated car. If anything forward bite may actually get a little worse by going softer on the 5th arm for a full-floated car.


When we used to run Clamped LR on LM's, adjusting the fifth coil spring will make a big difference. I don't think alot of guys figured that out. Anytime we ran clamped, we usually softened the torque arm 100# to 150# for the slick. I have no arguement there.

I can just see that a pullbar (depending on the whole arrangement) will rotate the clamp way more then a fifth coil will even with a soft spring. On my LM when I used a pullbar and a torque arm for braking (had a shock on it) it would bottom out the shock (which had about 4.5 of shaft showing). I have to move the shock up on the frame to add more travel (extra 1 1/2") and it would still bottom from time to time if the track had traction. You would have a hard time getting that much travel with a fifth coil unless the spring was very soft and then I could see it not wanting to hook up because the rate was way to soft.

Because the rear end goes forward it induces more pinion angle just because it has to take up this slack.

I just see that with a torque arm you will lose alot of upward pinion movement that you won't have with a torque arm. That is why I base my opinion on a torque arm is likely better on the hook then clamped. I'm sure it could be made to work as you did. I just think that over all, you'd be better on the hook then clamped.

[billetbirdcage]

any of you guys know of a company that offers a coil over dummyshock to mount a small spring for a lift bar like late model guys use. something thats not to over priced.


If your rules allow it, I have used a small body coilover set up like a midget or other small cars on the torque arm of a LM. This was to save wieght and run on a 2100# wieght rule.

You could look at Afcoracing.com and look at the small body shocks and springs, I doubt they are legal for you in a Mod as they are aluminum and the spring dia is smaller then a normal LM coilover. Aren't you rules a 5" spring?

[billetbirdcage]

you dont want to run an actual 90/10 on the end of a torque arm, its the wrong valving it is an easy out hard in, on the torque arm you want easy in hard out, like a 3-6 or 3-7.

If you generically mean 90/10 as a damper shock then i can see advantages both ways, but im still thinking, in general i think the 90/10 on top the housing tends to hurt sidebite because it kind of binds the car up not letting it roll as easy. You also run the risk of topping it out on acceleration if you get lots of pulbar travel and LR movmement. This can lmit pullbar movement and effectively make it a solid bar, but i think it can break the tires loose when it hits the top of the shock as there is no cushion left in the pullbar.

If you go with so sort of 90/10 above the rear end I'd use a 9" stroke shock to help eliminate any bottoming or topping out the that shock. I see this happen far to often on the MODS, I can't believe most are still using a 7" stroke shock here. Just one less problem you have to worry about. If you top out that 90/10 you will usually unload the rear tires and light them up on the straight.

[race81]

Bbc, Imca Regulates 4.5 Minimum Spring , Along With Some Tracks Are Ok With Rear Coilovers But Must Use A 4.5 Spring

[mbaker76]

We fought the problem of topping out the 90/10 shock for awhile when we first went onthe hook. Tried movng it around and finally got it to where we have good travel forward and rear. seems like when we got the rear travel good we were short on the front and vice versa. Its amazing how many people have never checked this. The biggest thing was stiffeneing up the pullbar, we would consistently get 2" travel but it was deceiving because the 90/10 was stopping it. Pull the 90/10 and youd get 3 1/2". We originally thought the pullbar spring was stiff enough because it only allowed 2" but we were wrong. Thats why we run the biscuit is because we cant find a spring stiff enough to put in the pullbar and limit travel like we need. Thats originally why i started thinking abuut this. I think clamped cars need the pullbar because they need more travel, to wrap the LR spring up VS. the floated setup where you dont necessarily need as much travel but you need the lifting effect to load the rear. Thats where my 1" travel came in... 3" on the end of the torque arm is about the same as 1" on the pullbar, due to leverage/ratios etc.

[Nascar8n1]

Interesting chat, we run the 4bar/4bar with fifth arm with on-hook setup. I must admit it was more work to figure out ,but we were bored with all the different setups and wanted to try this for change. I always thought the Latemodels are years ahead of mods so why not give it a try. We have 40 shows on this setup but also run IMCA and Wissota tires at 3 different tracks too. Takes more time but we feel it is as good as pullbar setup. You are all on right track go for it. It also does help to get info from RB or anyone willing to lend a ear. After all we all are racers lets stick together. Just a side note we hurt 3 motors with this setup so don't think for a minute she doesn't bite and love HP and torque. Let her buck!!!!!1

[race81]

mbaker, the 90-10 ill use is the same one that i use over my pullbar now. it is an hard in, easy out shock. you dont think this would work on the front of a lift bar? or do you think a more even compression and rebound would be better? we ran a liftbar when i first started racing, but didnt know enough to even think about experimenting with that shock. got a freind that had a 90-10 go bad and bind, you talk about something that can take the forword bite out of a car, just have one of those go bad.

[mbaker76]

Does your 90/10 run forward or backward from the rearend? a 90/10 damper above the pullbar running forward should be hard in/easy out.

[race81]

our 90-10 mounts at the rear axle and goes forword. it is a hard in easy out, sorry about the confusion, im all mixed up. but will it work or do you think a different ratio would be better?

[mbaker76]

you would not want to run it on the torque arm because the forces are opposite. on acceleration you are compressing the shock and on brake you are stretching the shock out, exactly oppostie of when its mounted on top the housing. IF you ran a true 90/10 shock on the lift arm then on acceleration you would be trying to compress the spring and the stiff side of the shock, on braking you would have virtually no damping because you are pulling against the soft side of the shock. You need a 3-5 to 3-7 something in that range not a 90/10.

[fourbar83]

Running a lift arm with 5th coil I run just as mbaker76 said, a 73/7 with out a 90/10 above the rear end. If your going to put the shock on the lift bar instead of above the rear end to dampen for the pull bar, you would need to custom order a 0-14 steel Afco take apart shock.

[race81]

thanx guys i had to run that through my head a couple of extra times to get it in my thick skull. sounds like if i go with this setup i may want to spend a lot of extra time on test and tune day!

[LM14]

I haven't read all of every post but here are a couple thoughts:

LM and Mod differ in 3 main areas. Width of the chassis, tire size and spring diameter.

With the wider stance of the LM, you can get away with a little more left/right location of the torque arm. 2" left or right within the track width of a car is a much higher percentage of movement in a mod than a lm. Might make some diference.

Tire size is (has to be) a factor.

The spring diameter used on mods would make the 5th coil at least 1.5" further to the right. That's a big change.

I still think a 750# Reese bar mounted in a short ladder bar (like a lift arm that's only 18" long) with a rubber bushed contact point was the smoothest torque device we ever had in a race car. If I ran a mod, that is where I would be looking these days.

JMO,
SPark

[mbaker76]

I did some measureing on our car this weekend and what I found was that due to the way the bottom 'X' was constructed it was going to limit the length of the arm anyhow. Until I have time to get into it furthur Im not sure I could fit a 36" or longer bar without making changes to the 'x'. The car has mounts in it to run a 32" brake arm, so all the pieces are there just getting a longer bar to fit is going to be the problem.

As far as the left to right placment. I agree that the narrower mod track is going to make it touchier. I guess you could somewhat help that by going to 2" off wheels all around and even an offset rearend housing to move the center section an allow the torwue arm to be furthur left. But then you run the risk of the driveshaft coming into the cockpit, and also shortens your panhard bar. But I beleive Pierce cars run a left offset housing so it is possible.

[profab00]

I don't know the width or off sets you have built into your car but I might suggest you talk to your frame manufacturer and get his input. I wouldn't change the car that much to do this. Go with the longest arm you can put in and increase the spring rate for the shorter arm........yes, had to think if I was backwards or not there. As far as a reese bar, Sparks speaks loads. On certain types of surfaces with certain types of suspensions, I'd take it anyday over a jerk rod.

[KTM-Lew]

Seems like the fiberglass slapper deal would be easy to adapt?

[mbaker76]

our car is by a local builder, and I had some input on the build, so its partly my fault because at the time we werent planning on ever running a lift arm. I still think it will fit, just gonna take even more than what i originially thought, but thats how it goes. Ive got all winter to mess with it and see what i come up with.

[race81]

mbaker, i know where your coming from on the x-brace deal. our cars brace is made of 3/4 by 2 inch rectangular tubing. im hoping to set ours on a jig and possibly relocate a little. do you think that if your car is front heavy that the further forword you can mount your spring with a longer bar the better? sounds logical, maybe work off of a teeter totter effect to transfer weight under throttle conditions. is there any formula to fugure center of gravity of a car using your current wheel weights? be interesting to try and figure it out.

[mbaker76]

If you know rear % and left % numbers you can find it pretty close.

say you have a track width of 62" and 52% left side weight, that means 52% of 62"=32.25"-31" (half of track width) =1.25" so your center of gravity is roughly 1.25" left of the centerline of your car.

110" wheelbase with 58% rear, 58% of 110=63.8" back from the front wheels or 46.2" forward of the rear wheels.

So your center of gravity is roughly 46" forward from the rear axle and 1" left of center line. Keep in mind thats just kind of a rough estimate because different track widths front and rear and having the rear offset left or right will affect the true centerline of the car. But it will get you in the ballpark.

[Nascar8n1]

Couple quick things we do on this setup is move motor to right and up, to compensate the lifting of RF. The fifth is right next to drive shaft and on our mod the 6th is at 39" and we run 5th at 32" ,change spring from 350 for heavy to 225 for dry we run a bilstein 60/20 and 35/30 for heavy, and yes you need the bars set wide on LR and close on rr we run 275 to 325 spring on LR when tacky and 200 to 250 dry with 150lbs bite to 180lbs max. Its actually fun to play with this, espicially when people look underneath and ask how in the hell do you get this to work. Their is more fine tuning like running 20/60 shock on LR when slick and slow, And last the driver needs to play with his driving habit, like trail braking and smooth driving, a soft shock in RF to hold her down is helpful also. My drive says it feels as if the RF is flat. A good motor!! is a must and just to tell you how good this is we have passed latemodels on test and tune days.