bar angle split

[mbaker76]

Is there a general rule for bar angle or limits on how far to split them side to side. Meaning LRU vs RRU. Seems like I see most sheets, or books etc say to start with the LR 1 hole or 5* higher than RR, but is there a limit or range to stick to, is 10* too much or 15* or does it matter as long as it works?

On our car (its a mod) we currently have 24-25 in the LRU and 14-15 in the RRU with driver in the car. The car seems to work really well when its dry but I dont see many others with that much angle in the LR or at least it doesnt look like that much angle anyway. Just wondering if we are missing something and using excess LR bar angle to compensate. We have since tried to take out a little 3-4* LRU angle but it lost bite off the corner and heat out of LR tire. Could it be that with the lower angle on the LRU the car stays on the bars but is loading more through the pullbar, wheras with more angle in the LRU the bars are keeping the car up thus loading that tire more. In other words in example one the pullbar is the main lifting force wheras in 2 its the LR bars? Maybe that is why late models with lift arm coudl run more RRU angle to keep the car freed up? And also why mods with a zlink work well, because the lower loading from the z link is made up for by the pullbar?


here is the rest of our bar setup
LRU 25 RRU15
LRL 2 RRL -3
pullbar at 14* down

[mbaker76]

forgot to mention it is LR behind RR in front 4 bar both sides and also jbar center of pinion 5" split with driver.

if it matters........

[Rocket Bonehead]

The split in angle between the LR bars and RR bars is insignificant, or at least, that is how I view it. What is more important, for each corner, is the split in the angle between the upper bar and the lower bar. Obviously, this would be more important on the LR than the RR (in terms of the car getting on the bars).


I approach each side as a seperate entitiy, and to break it down even further, I approach each BAR seperately as well. BUT, for each car there is a 'sweet spot' (certain bar settings) on each corner that allow the car to be at it's best and most consistent (different settings for different conditions). Obviously these settings will be different for each car and are determined by bar lengths, angles, motion ratio, pull bar or lift arm, PH Bar settings, etc... (many factors).


There are a couple of different 'theories' or 'views' on making bar changes and how they affect the car (I think the main arguments revolve around the RRT and LRB rods). I could tell you how I approach things and how I use the bars, but Billet, JJ, Timmay, etc... could each come on here with a different approach to achieve the same result. So long as you're running consistently and running up front, then whatever approach you are using is the correct one (for your situation).


Anytime you start worrying about 'general rules' in terms of making changes, then you are only serving to handicap yourself from learning about your car (in my opinion). Just because one guy does one thing doesn't mean it will work for you, regardless of whether or not the have the same brand of car. If someone asks me for help, I can only tell them what I know and have seen work based on my experiences, BUT my suggestions might not fit their situation.


It sounds as if you learned something about your car by moving that LRT rod. Sure, the performance wasn't as good, but you did learn that by trying the change. Try some other changes (one at a time), record the results in your notes, and you will find out very quickly where your car likes to be.


Your current angles would fall into the fairly common range for each bar on most 4-link cars, but that doesn't make them the right, or wrong, angles. So long as the car works, it doesn't matter if you're running -3 deg on the LRT bar (strictly an example). All that matters is whether or not the car works.



RB

[mbaker76]

Thats what i hoped to hear, but couldnt convince myslef of it. When we started this year i told myself i wasnt going to worry about what every body else was doing i was only going to worry about our car. I dont know how many times the driver comes to me and says, so and so did this, or has their bars here, or has a weight here, etc etc. I have to remind him that so and so has different car, or different mounts, or different ?? you get the point, but in the back of my head i always think what if there is something to it so and so. There were about 5 or 6 new cars like ours this year and they were all pretty fast early but nobody really seemed to mess with them much, we kept tuning ours little by little then when it dried out there were nights, we were almost as fast on dry as we were on tacky early in the year, where some of the others were fading. Then last week we get a heavy track again and everyone else was fast again but we didnt make the right changes at the right time and our car was setup a little too aggressive and....lets just say it was frustrating to driver and crew. But we learned something and thats what matters.......

quote:
Anytime you start worrying about 'general rules' in terms of making changes, then you are only serving to handicap yourself from learning about your car (in my opinion). Just because one guy does one thing doesn't mean it will work for you, regardless of whether or not the have the same brand of car. If someone asks me for help, I can only tell them what I know and have seen work based on my experiences, BUT my suggestions might not fit their situation.

I am glad you said that because i have found myself thinking more about individual changes and how many things that affects or how it affects our car instead of just typical cover all adjustments that you see in all those adjustment guides out on the net. Half the time i think some of those were written in leaf spring days and 50% doesnt even appply to 4 link cars.

quote:
There are a couple of different 'theories' or 'views' on making bar changes and how they affect the car (I think the main arguments revolve around the RRT and LRB rods). I could tell you how I approach things and how I use the bars, but Billet, JJ, Timmay, etc... could each come on here with a different approach to achieve the same result. So long as you're running consistently and running up front, then whatever approach you are using is the correct one (for your situation).

If you have a chance I would like to hear your theories on those bar changes, it cant hurt to hear somebody elses ideas once in awhile.

[billetbirdcage]

I look at this similar to RB (mainly look at individual bars), but I also look at the entire package together.

Spreading the bars alters the spring rate and can be used to do things not possible other ways.

Example: Raising the RRU bar, this will increase the effective spring rate on that corner. The added bar angle will loosen the car on exit from rollsteer and thrust angle, but I feel it will also tighten entry (added spring rate). While I haven't heard RB say or agree with this, for us it is there. It is something you can think about and will help you understand soem of the things going on, but shouldn't be the only factor you go off of.

So if you wanted to loosen exit but didn't want any tightening of entry you might raise the upper bar and soften the spring some to make the effective spring rate the same on entry but have the added rollsteer and thrust angle off.

[Rocket Bonehead]

Billet's example of the RRT rod is what I was refering to as one of the different views we might have. I know for us, adding angle to the RRT rod does not affect the car on corner entry (at least my driver notices no difference). I am not saying that the effect isn't there, but just that my driver doesn't notice it (or hasn't yet).


I would definitely agree that adding angle to the RRT rod will free the car up from the center out.



RB

[billetbirdcage]

I don't have my guys raise the RR bar on the traction for this reason. It tightens entry which in the traction we don't want, so the RR bar usually stays in one place. You could weld the thing there and I wouldn't have a problem with it.

I can see it easy to miss the entry part as you are usually driving aggressively in the traction and may go un-noticed.

It is just an adjustment we don't use and adjust the car elsewhere.

Whose right? both/neither just different ways to get the job done.

[mbaker76]

lets take 2 different scenarios here
1) the car is tight in middle and continues all the way off the corner,
2) the car is tight in middle but if you get it turned its good coming off


In #1 since it is tight all the way off would an upper bar adjustment like raising the RR or lowering the LR help more than a lower bar adjustment because its a traction bias problem through 50%+ of the corner.

In #2 (which is more common for us) Would raising the LR lower bar be a good adjustment just to take out some intial drive and free the car to turn but not affect coming off as much?
Also have thought about stiffenening LR spring or taking out LR bite to keep the car from rolling up as easy creating more bar angle on its own, to me this seems like more of a timing deal than anything, you are still going to get to the same point your just delaying it a little bit longer into the corner.

We have tried raising the RRU before and it did loosen exit but driver also felt it tightened entry some. When there was good traction i dont think the entry was that noticeable but once it slicked up a little he felt like it was tighter in and once it turned it was loose off and wanted to keep coming around on him. But i coudl see where moving the bar and changing spring rate would work together. In the past 3 years we have only messed with RRU maybe 2-3 times, so its also hard to say if we really gave it a good shakedown either.

[billetbirdcage]

Hard to base exit handling when the car is tight in the middle as usually this will mess up exit one way or the other.

Example: by fixing the tight in the middle you will ususally preceive the forward bite is better just because you aren't busting the car loose or have more monentum thru the middle now.

With #2, I'd be more inclined to go with the LRL bar. But if it is just an instant traction problem in the middle I'd look at the LR rebound and try to increase it and remove this problem. I know that isn't as easy with a mod because of the no ajustable shock rules.

[Timmay]

Middle is a little vague. Is it tight right before you pick up the gas, or is it tight right after you get in the gas?

[mbaker76]

At this point the scenarios were hypthetical but what I was eluding to was a car that is tight when you first get back on the gas like it has too much inital LR drive.

[Timmay]

If I just wanted to loosen up when you picked up the gas initially, I would either:
* move both right side bars up the same amount
or
*move both left side bars down the same amount

Doing either of these will not significantly effect entry or in the middle before the gas.

Both of these will loosen exit, but doing the right side bars will have a little more loosening effect than the LR bars in this case.

Good Luck!

[Rocket Bonehead]

lets take 2 different scenarios here
1) the car is tight in middle and continues all the way off the corner,
2) the car is tight in middle but if you get it turned its good coming off


In #1 since it is tight all the way off would an upper bar adjustment like raising the RR or lowering the LR help more than a lower bar adjustment because its a traction bias problem through 50%+ of the corner.

In #2 (which is more common for us) Would raising the LR lower bar be a good adjustment just to take out some intial drive and free the car to turn but not affect coming off as much?
Also have thought about stiffenening LR spring or taking out LR bite to keep the car from rolling up as easy creating more bar angle on its own, to me this seems like more of a timing deal than anything, you are still going to get to the same point your just delaying it a little bit longer into the corner.

We have tried raising the RRU before and it did loosen exit but driver also felt it tightened entry some. When there was good traction i dont think the entry was that noticeable but once it slicked up a little he felt like it was tighter in and once it turned it was loose off and wanted to keep coming around on him. But i coudl see where moving the bar and changing spring rate would work together. In the past 3 years we have only messed with RRU maybe 2-3 times, so its also hard to say if we really gave it a good shakedown either.


For both, senarios, I would make sure that the car isn't too tight on entry as that will likely also cause you to be tight in the center.


That said, to help the middle in both senarios, I would index the RR. If that isn't enough, then I would either take angle out of the LRT bar or add angle to the LRB bar.



This is all speaking generally of course. Without knowing how the car is on entry, or the rest of the perameters of the setup, it is hard to say if those bar changes would help enough.



RB

[mbaker76]

i dont often hear of many people indexing the RR. I assume you mean on the cage, but what advantage is there over just adding angle to the bar on the frame.


We are heading to a track this weekend (Lakeside Speedway, prob rings a bell with Billet) that is normally heavy and fast with farily wide sweeping turns, compared to our weekly track which is dry, and tight cornered. Unless we make some changes the car is always very very tight with our 'normal' setup and he always comes in and tells me how the things wants to drive him into the wall. I am thinking of raising the jbar 1 hole on the pinion to free all around and then after that i am debating on what to do if its still tight on the gas. At first i thought about he LRL but your barely out of the gas on entry so even if you delay the initial drive your right back on the gas and locked down really early into the corner, so thats why i thought about lowering the LRU to try and take some drive away all the way off. The other thing we have done in a pinch and short on time is move the RR out 1" and stick a spring rubber in the RR spring just because you are on the gas and turning under power so much i dont think it affects the car on entry like it would off the gas rolling in.

[billetbirdcage]

One thing to keep in mind with index on the cage, is the location up or down from the centerline of the axle. If you index down the upper bar (1"), then the upper bar is 1" closer to the center of the axle then the lower bar is (3.5" vs 4.5"). This works just like a brake balance bar, it will put more of the forward pressure of the rearend on the upper bar then the lower bar. Generally, since the upper bar has more angle then the lower is will lift easier.

Obviously as the bar lengthens or shortens (horizontially) from suspension movement, the closer to the centerline of the axle it is the more it will move the top part of the car forward or back.

You could sit down and figure it out and see how much, but on the RR with the same total bar angle but with one indexed an inch down would more the RR back more under roll then the same angle not indexed.

Indexing is fine on the RR, but I would refrain from doing so unless there is traction in the track.

That was a quick reply and no proof reading and a quick read of your post, busy right now will go over later.

[billetbirdcage]

One thing about lowering the LRU bar, if the car is all the way up (to the stop-which is likely at lakeside) then lowering it is only going to lose some rollsteer as it is still lifting the same amount but now the LR isn't going as far forward due to the reduced bar angle.

If that is the case I'd go with Timmay raise both RR bars, to increase rollsteer and drive angle on that side.

[mbaker76]

Thats something I had never really thought about trying. I guess that would free the car all around and not really change the effective spring rate on the RR so it should not mess with entry too much right? Whereas if you only raised the top bar, changing bar split then it would/could affect entry because you are changing the effective rate.

I have heard of some guys who only tune the car with the RR, they set the LR bars and leave them and then tune for the track with the RR. Anything to this? I can see where if your up against the limiter on the LR then about the only thing you can tune would be the RR so maybe there is something to it.

At Lakeside it will be against the limiter all the time, only when you enter and back off just to hit the brakes a little will it come down, then its right back up. I have thought about shortening the chain some to free it up on the bars and keep the car calmer. I have looked at some of the cars there and always amazes me how tight you would think they should be, Bar angle on LR something like 20-25 and level lower, then RR 4 bars pretty shallow, maybe 15* and level lower, The thing that gets me is the z links that are level, or maybe even uphill to the frame on the rear and downhill to the frame on the front.

How much will moving the RR out 1" help free the car all around? I know this puts more left in the car which should help free it in, and also moves the thrust angle to the right which should help free it out some too. I have heard guys using 1/2" spacers to free it up some so I would think 1" should be noticeable.

[mbaker76]

The more I think about it i think we were already adjusting with the RR we maybe jsut didnt realize it. Last year when we were there we had taken some bar angle out of LR before hot laps but didnt have time to make any big changes for the heat race and really needed to loosen it up on the gas so we stuck a spring rubber in the RR. It worked as it freed the car on the throttle and off the corner, and we have since done that on a coupel occasions when the tracks have been really grippy and you can really drive it hard and then stand on the gas. Now thinking back not only were we stiffening the spring which should add drive but also not letting the RR roll as far keeping more anlge in the bars for more drive from RR. Any tightness on entry wasnt noticed because you coudl simply drive past it or through it. Make sense?

It worked for a quick adjustment when we knew the track would only stay heavy through heat races and would go to slick by features. Then we could pull the rubber out and be back to normal. Maybe in a long term scenario though moving the bars would be a better choice and then use spring rate to adjust entry some if needed.

[billetbirdcage]

I have heard of some guys who only tune the car with the RR, they set the LR bars and leave them and then tune for the track with the RR. Anything to this? I can see where if your up against the limiter on the LR then about the only thing you can tune would be the RR so maybe there is something to it.

Some guys maybe, but I think they are in the minority not the majority. We rarely move the RRU.

Even if you against the limiter, bars still affect rollsteer and instant traction. If you limiter is an underrail or chain (not on cage) then you are stopping the rear end in the same place everytime (so many inches of lift). If you added bar angle to the upper you still have the same lift (wedge) but more rollsteer therefore the car will turn better at the part of the track it is against the limiter. Obviously the added bar angle will make the car stay there longer (out the corner or down straight) and get there quicker.



At Lakeside it will be against the limiter all the time, only when you enter and back off just to hit the brakes a little will it come down, then its right back up. I have thought about shortening the chain some to free it up on the bars and keep the car calmer. I have looked at some of the cars there and always amazes me how tight you would think they should be, Bar angle on LR something like 20-25 and level lower, then RR 4 bars pretty shallow, maybe 15* and level lower, The thing that gets me is the z links that are level, or maybe even uphill to the frame on the rear and downhill to the frame on the front.

There can be a fine line here: depending on how far the car is getting up or where it is limited at. Say the car is on the stop and you took chain out of it to reduce the travel, this could loosen the car or tighten the car. If the car was up far enuff that the rollsteer vs lift curve got high enuff to the rollsteer side that if you reduced the lift some you have decreased the rollsteer alot and may tighten exit. The opposite is also true is the car is being stopped before the rollsteer starts overcoming the lift then limiting travel will likely loosen the exit.

For Lakeside it is hard to bow a car up enuff to make it turn in the traction and usually reducing the travel will help lossen exit, but could be different depending on attitude of your car.

Hope that makes sense, may be hard to follow me.


How much will moving the RR out 1" help free the car all around? I know this puts more left in the car which should help free it in, and also moves the thrust angle to the right which should help free it out some too. I have heard guys using 1/2" spacers to free it up some so I would think 1" should be noticeable.

I personally never felt a huge change in a LM with a spacer on the RR it was usually minor and more noticable on the RF, on a mod I have no idea as to how big of a change that would be.

[mbaker76]

the thing is we are against the limiter nearly instantly when you are on the gas and stays until you lift. I think this is where the Late models and mods differ, I can watch the lates and see the car settle back down headed down the straightaway but with a mod and a pullbar it stays up until you lift, or until you lose traction. So once your on the gas 90% of the time your against the limiter until the next corner.

see what you think of this....
In my mind I think thats why lates can get by with more rear steer, dynamic or static, because they dont hold it (or dont hold as much of it) as far around the track. The car steers to get around the corner but then when it settles back down coming off the corner some of the steer is taken out and it drives off straighter. With the mods once your on the gas it steers and stays that way all the way down the straight and with a lot of steer to the outside and the rear getting traction it sometimes pushes the front end up the track and feels pushy, even though the steer helped turn the car in the middle.

[billetbirdcage]

To a degree, yes. We are now doing things to let the cars settle more shortly out of the corner to make the cars drive straighter on the straights and therefore go down the straight better.

I would also think the COG might be higher in a MOD the a LM which is going to add lift to the left side (anytime there is lateral G's in the car) and help hold the car up. Combine this with a pull bar that has angle in it, I would say they are more likely to stay up then a LM.

There are differences between the two, but both are very similar. It just seems like the mod's are about a 1 1/2 years behind as far as tech and set-ups as compaired to a LM. Meaning a typical 4-bar hook mod is similar to what a LM was running a year or two back.

[mbaker76]

I agree on mods being behind. I dont know of any mod builder that really has a good 'hook' setup right now. There are many cars running that way, but i dont know of many builders that have dedicated their cars to being on the hook. Shaw's are pretty good, and Skyrockets now have a hook option but thats about all i know of, or at least know of that are doing decent.

Maybe it wouldnt work but i would like to try a mod with a lift arm instead of pullbar. Maybe with the smaller tires the lift arm just wouldnt work as well, but i'd like to give it a try. I just wonder if the pullbar was a carry over from the 2 link or clamped up days and if its really needed when on the hook. If you look at our car right now it only has about 12-14* pullbar angle in it, as soon as the car starts to go up you lose a bunch and its almost completely flattens out, so its not really doing anything more than apllying forward pressure on the rear housing. But maybe thats why it works better with the small tires, wheras the lates with big tires have enough natural traction they can keep the car loaded themselves.

[BSR12]

The RRT rod, from the top hole to next hole down what effect does it have on car?
should you move the bottom rod down with it or leave in same hole?
What are theries out there?

[Rocket Bonehead]

Removing angle from the RRT rod will take RR drive away from the car, along with loose roll steer, which will make the car tighter from the center out. Some say it will loosen the car up on entry as well, but I haven't had that problem with my driver.


I would suggest making one bar change at a time until you learn what each does and how big of an effect they have on your car. After that you can start to put together multiple changes, with some degree of accuracy, based on that knowledge. Renting a track for testing, or going to a practice night, would be a good way to try individual changes.



RB