Stiff rear
08-02-2016, 02:23 AM
#1
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Thread Starter
Stiff rear
Hi guys, I have a 2007 ZO6 with ZR1 sway bars front and rear. Have DRM shocks all the way around and the car is lowered all around on sticks bolts. I'm running Toyo R888s and the rear seems real stiff? On most of the road courses if I climb a little elevation as I go over the top the *** end pitchs left and get loose at high speeds. I'm talking speeds of 110 to 130. Any ideas on what could be the problem. I do have a track alignment which is pretty aggressive. Thanks ahead of time for your help., just trying to get those lap times down!
08-02-2016, 10:51 AM
#4
Max G’s
Hi guys, I have a 2007 ZO6 with ZR1 sway bars front and rear. Have DRM shocks all the way around and the car is lowered all around on sticks bolts. I'm running Toyo R888s and the rear seems real stiff? On most of the road courses if I climb a little elevation as I go over the top the *** end pitchs left and get loose at high speeds. I'm talking speeds of 110 to 130. Any ideas on what could be the problem. I do have a track alignment which is pretty aggressive. Thanks ahead of time for your help., just trying to get those lap times down!
08-02-2016, 12:23 PM
#5
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Thread Starter
l98tpi the car is fine on the staights not loose or light at high speeds have a rear spoiler and the car is fine. ran 178 mph at Auto Club Speedway and all was fine. Its just going over a little hill and at the crest it pitches left. DRM shocks are not adjustable.The car has very little rake to the front.It just feels so stiff on the rear like it jumps over the crest of the little hill and pitches left. Could ZR1 sway bar be to stiff? Thanks for the help.
08-02-2016, 01:45 PM
#6
Burning Brakes
You might be experiencing some bump steer given the fact the car is lowered. It probably most noticeable when the car gets light. I'd check the whole alignment and have someone check bump steer. Again....has the car ever been corner balanced?
08-05-2016, 01:51 AM
#8
Tech Contributor
As Hi Volts keeps hinting:
[1] Track cars need an inch or two of chassis rake - down-in-front.
[2] A performance shop can do a corner balance, and the total weights on each side need to be within a couple percentage points of each other. (There are MANY threads here dealing with the subject - search.)
[3] Beside lowering the car, have you done anything to limit air entering under the car? When sudden changes in elevation effect handling, frequently aero is the problem, BUT - simply applying downforce is seldom the remedy.
Until you have a known setting for rake, alignment specs, and corner weights, you'll be chasing your proverbial tail.
Ed
[1] Track cars need an inch or two of chassis rake - down-in-front.
[2] A performance shop can do a corner balance, and the total weights on each side need to be within a couple percentage points of each other. (There are MANY threads here dealing with the subject - search.)
[3] Beside lowering the car, have you done anything to limit air entering under the car? When sudden changes in elevation effect handling, frequently aero is the problem, BUT - simply applying downforce is seldom the remedy.
Until you have a known setting for rake, alignment specs, and corner weights, you'll be chasing your proverbial tail.
Ed
08-06-2016, 03:41 PM
#9
Tech Contributor
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How low did you take the car? You may be running out of suspension travel and bottoming the car on the bump stops. That can cause the backend to move sideways on some bumps that depress the suspension more than others. My C6 Z had this problem and it only showed up on certain bumps. The second turn in the uphill Esses at VIR was particularly nasty since the backend would pitch left if the car speed was over 102 mph or so.
Bill
Bill
08-06-2016, 05:01 PM
#10
Instructor
As Hi Volts keeps hinting:
[1] Track cars need an inch or two of chassis rake - down-in-front.
[2] A performance shop can do a corner balance, and the total weights on each side need to be within a couple percentage points of each other. (There are MANY threads here dealing with the subject - search.)
[3] Beside lowering the car, have you done anything to limit air entering under the car? When sudden changes in elevation effect handling, frequently aero is the problem, BUT - simply applying downforce is seldom the remedy.
Until you have a known setting for rake, alignment specs, and corner weights, you'll be chasing your proverbial tail.
Ed
[1] Track cars need an inch or two of chassis rake - down-in-front.
[2] A performance shop can do a corner balance, and the total weights on each side need to be within a couple percentage points of each other. (There are MANY threads here dealing with the subject - search.)
[3] Beside lowering the car, have you done anything to limit air entering under the car? When sudden changes in elevation effect handling, frequently aero is the problem, BUT - simply applying downforce is seldom the remedy.
Until you have a known setting for rake, alignment specs, and corner weights, you'll be chasing your proverbial tail.
Ed
This. Especially since you indicate it is occurring when you crown a hill at high speed. Spend some time on rake, alignment, and your air dam and splitter. Replace the side pieces on the air dam if they are worn down. If your center dam section folds back easily, mount a couple of L brackets behind it to help hold it vertical at high speed. If your splitter has taken a beating, make sure it is set back in the right position and attached properly. Make sure your brake ducts are attached and allowing air to come in from in front of the dam properly.
Set alignment after rake and weighting of course.
Last edited by CONE RACER; 08-06-2016 at 05:02 PM.
08-12-2016, 02:46 AM
#11
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Thread Starter
I've lowered the car about 2" in front and the same in the rear. It does have a rake front to rear. All the aero on the front is still stock 07 ZO6 and no splitter? I do need to check the air dam center and side pieces as they hit every little bump on the road when I drive it on the street. So you could say I haven't done anything to limit air getting under the car. Alignment is a track setup I had done after I put the R888s on. Thanks guys so much for the help. Bill Dearborn you could be so right! Might have to raise the rear a little.
08-19-2016, 07:56 PM
#12
See if you can measure the toe change in the rear suspension in its full range of travel.It sounds like the rear wheels might be going toe out when the suspension is unloaded.Getting the car really low isnt always the solution to best handling.If the car has no travel left in the shocks it will dart around.
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