rear suspension option

[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?