Looking for some rear susp tuning help.
10-16-2010, 08:22 PM
#1
Looking for some rear susp tuning help. I have been searching this place all day and the stickies and I still have some questions for you guys that have been at this awhile. Last year we cut a 1.43 60' with the torque arm in the 2nd lowest hole up front (short arm) and the front shocks set at 1 ext and 10 comp. Rear shocks set to 2 ext and 3 comp. It would pull the tires in 1st and 2nd gear after it would hook.
I have since changed the tq arm to the highest hole and the front shock settings to 2 ext and 10 comp with the rear shocks at 2 ext and 8 comp. The car barely lifts the left front tire off the ground but it seems to be spinning out of the hole or unloading the rear tire too quickly only getting us 1.50's 60'.
I thought by raising the tq arm up higher would put more force on the rear tires but from what I am reading this is the opposite?? I need to lower the tq arm back down to put more force on the rear tire?
I am in the process of a ARB and getting the IC stuff figured out just looking for some basic susp info. Thanks.
I have since changed the tq arm to the highest hole and the front shock settings to 2 ext and 10 comp with the rear shocks at 2 ext and 8 comp. The car barely lifts the left front tire off the ground but it seems to be spinning out of the hole or unloading the rear tire too quickly only getting us 1.50's 60'.
I thought by raising the tq arm up higher would put more force on the rear tires but from what I am reading this is the opposite?? I need to lower the tq arm back down to put more force on the rear tire?
I am in the process of a ARB and getting the IC stuff figured out just looking for some basic susp info. Thanks.
10-17-2010, 09:43 AM
#2
Assumming your tire psi is coorect for conditions and shocks r good. More RB is what I would be tinkerin with. I start at 50/50 on the rears, 0/100 on the fronts. I never touch the ta. What bar is out back. Adj roll? I have success loading the pass side a hair more.
If you have a vid on the launch it would help see whats goin on.
If you have a vid on the launch it would help see whats goin on.
10-17-2010, 10:55 AM
#3
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You took a bunch of squat out of the car with what you did - moving the instant center up and tightening the shocks... With a manual, you need some of that squat to absorb the hit of dumping the clutch. What you went to is more towards a setup that would work on an automatic with a stall converter. Put it back to where you were, and make very small changes on the shocks to fine tune it...
10-17-2010, 01:24 PM
#4
I do not have any videos of the runs. I agree with taking squat out of the car. Between the compression being almost full hard and the tq arm up high. Was trying to get the car to force the car forward instead of in the air but I guess there needs to be a happy medium.
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10-17-2010, 05:25 PM
#8
chassis separation forces the rear down and the body up. You want to limit this. Rebound shock tuning will help. When I ran that tire usually started at 10lbs in the sun and 13 when it was cooler. Depends how good the tires are and track conditions. It can be a mind **** at times.
10-17-2010, 09:09 PM
#10
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Good info. We have been playing with our new combo. I just moved my arm up 3 holes. It's an auto. I looked at the rear control arms and they are pointing down towards the front. Time for some relocation mounts. 03 Busa did you check your control arm angles? Oh and tuning shocks is a PITA. We are trying to hook our car up on 18" drag radials. Good Luck.
10-19-2010, 06:51 PM
#11
So let me ask this another way. If I was at the 2nd from bottom hole and it would pull the tires in the first 2 gears then I put to the top hole it would not and I lost 60'. So by putting the arm to the lowest hole and the LCA's to the lowest hole that would plant the tires the hardest? Not that is what is right just trying to figure which way adjustments are working. So by lowering the lca's on a 4 hole setup and having the angle even more does almost the same as lowering the tq arm?
10-19-2010, 08:29 PM
#12
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It has to do with where they intersect. If you were to draw lines from each one where do the lines cross. The closer they are to the center of gravity of the car or even behind it the harder it should hit in theroy. Thats why the short Torque arms work well. Do a search for Baseline Suspensions .com it explains it in detail.
On my car the rear arms are pointing down with the stock mounts they will never intersect the t arm. Thus they are working against each other. I raised my arm the other day thinking it would help Thats what one web site tells you to do. It states that raising the arm forces the rear to plant better. I'm going to put mine back almost level and try to raise the rear arms. I am also going top find the CG of the car.
Your car should hit harder with the arms in the lower postion. If you hit to hard it may unload the rear or over power the tires thus slowing you down.
On my car the rear arms are pointing down with the stock mounts they will never intersect the t arm. Thus they are working against each other. I raised my arm the other day thinking it would help Thats what one web site tells you to do. It states that raising the arm forces the rear to plant better. I'm going to put mine back almost level and try to raise the rear arms. I am also going top find the CG of the car.
Your car should hit harder with the arms in the lower postion. If you hit to hard it may unload the rear or over power the tires thus slowing you down.
10-19-2010, 08:38 PM
#13
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I can find info for 4 link cars like the Fox body stangs etc. The torque arm set up is different. It's not a ladder bar nor a 4 link or a leaf spring with a snubber. What does the arm really do on a drag set up? Does it keep the rear from rotating like the upper bars on a 4 link? I know it adjusts the pinion angle. The shocks are used to control the speed at witch all this happens. they basically fine tune the movment of the suspension. I think.
I think if you put the arm to low it will point down to the ground. Not good again.Then the T arm will be working aginst the rear control arms. Have you checked your pinion angle after adjusting your T arm. It will change.
I think if you put the arm to low it will point down to the ground. Not good again.Then the T arm will be working aginst the rear control arms. Have you checked your pinion angle after adjusting your T arm. It will change.
10-21-2010, 01:37 PM
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I think some of it will. My thinking is that the T-arm acts like your upper arms and then the lowers are the same on both types. I was reading an article in GM High Tech about Mad Man doing a race suspension and they quoted him as saying that the torque arm angle was very important to these cars. I'll post the issue later. You are correct about the T arm being in the lower position. They had this car set up with the arm pointing down like neg 1-2 degrees He also said that the pionion angle wasn't as important as long as the drive shaft wasn't in a bind. They scaled the car on each wheel and talked about having the suspension square and adjusted the shocks to compensate for the weight inbalance.
10-21-2010, 09:12 PM
#17
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http://www.gmhightechperformance.com...uspension.html
Try this link. Or do a search mad man torque arm it should show up.
I'm still confused on the arm angle. I sent an e-mail to UMI to ask them where to measure from. I'm thinking now when you raise the front of the arm up into the drive shaft tunnel you are making the rear of the arm negative and that is the way it should be set up. Mine is at neg 2 or 2 down.
The drive shaft is at neg 2 and the rear is at a pos 1 so my pinion is a neg 1.
I'll live with that. My rear control arms are at a pos 5. That is bad they should be a neg 2-3.
My rear is within a 1/8 '' side to side and 1/8" fore to aft. I'll adjust them when I do the relocation brackets.
Try this link. Or do a search mad man torque arm it should show up.
I'm still confused on the arm angle. I sent an e-mail to UMI to ask them where to measure from. I'm thinking now when you raise the front of the arm up into the drive shaft tunnel you are making the rear of the arm negative and that is the way it should be set up. Mine is at neg 2 or 2 down.
The drive shaft is at neg 2 and the rear is at a pos 1 so my pinion is a neg 1.
I'll live with that. My rear control arms are at a pos 5. That is bad they should be a neg 2-3.
My rear is within a 1/8 '' side to side and 1/8" fore to aft. I'll adjust them when I do the relocation brackets.
