Rear end "walks" when accelerating...
Thread Starter
C3 Corvette Enthusiast
Joined: May 2008
Posts: 1,071
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Rear end "walks" when accelerating...
1995 LT1 Coupe, 81,000 miles.
Yesterday I had two new tires installed on the rear of my Vette. After the installation I noticed that if I was at cruising speed and gave the accerator a nudge, the car would slightly aim for the center line and would have to be corrected by steering, the opposite for deceleration (without using the brakes). Also, on the interstate (which has a segmented surface - segments about 20 feet apart) the rear of the car feels like it's "floating". It doesn't do this on smooth roads.
All 4 shocks were replaced last years (about 8,000 miles ago) with KYB units.
So, any ideas of what's making my car feel like a mid-60's car than a Corvette?
Yesterday I had two new tires installed on the rear of my Vette. After the installation I noticed that if I was at cruising speed and gave the accerator a nudge, the car would slightly aim for the center line and would have to be corrected by steering, the opposite for deceleration (without using the brakes). Also, on the interstate (which has a segmented surface - segments about 20 feet apart) the rear of the car feels like it's "floating". It doesn't do this on smooth roads.
All 4 shocks were replaced last years (about 8,000 miles ago) with KYB units.
So, any ideas of what's making my car feel like a mid-60's car than a Corvette?
Drifting
Joined: Dec 2005
Posts: 1,313
Likes: 2
From: High Ridge Missouri
Check all rear suspension bushing (including bat-wing), tie rod ends and wheel bearings. You've got play/someting worn out somewhere. Usually, but not always with that complaint it's a tie rod end.
Thread Starter
C3 Corvette Enthusiast
Joined: May 2008
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Wear bars in the center of both tires showing, more tread on the edges, smooth, even wear on both tires, no different wearing on the sides of either tire, no cupping, etc.
I usually run 32 psi air pressure but the tire guy told me that the Vette is so light in the rear, along with having such a wide tire (285-40ZR17) that I should run 26-28 psi in the rear.
I usually run 32 psi air pressure but the tire guy told me that the Vette is so light in the rear, along with having such a wide tire (285-40ZR17) that I should run 26-28 psi in the rear.
Thread Starter
C3 Corvette Enthusiast
Joined: May 2008
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Really, the "floating" feeling on the interstate is scary - it almost feels like the rear end wants to break free and throw the car out of control.
Team Owner
Joined: Sep 2003
Posts: 20,179
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From: Freedom is never more than one generation away from extinction.
St. Jude '03 thru '24
So you did or did not have an alignment with the new tires?
If so what were the final specs?
Last edited by JrRifleCoach; Jun 18, 2009 at 02:32 AM.
Thread Starter
C3 Corvette Enthusiast
Joined: May 2008
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So anything in particular to have done or ask the technician?
Safety Car
Joined: Nov 2004
Posts: 4,991
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From: The Pines South Jersey
check the footprint of the new tires that recommended pressure they told you is low, your rims are the proper width for the tire - you dont need to compensate the air pressure to get the proper contact patch.
Go with you gut and add to 32psi and heat cycle them a couple times, air is free.
Go with you gut and add to 32psi and heat cycle them a couple times, air is free.
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Team Owner
Joined: Aug 2008
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From: Rochester NY
St. Jude Donor '09 thru '26
The first thing (and easiest) is to go back to the air pressure you previously were running. If it solves the problem fine, if not you have eliminated one possibility at no cost.
Even if it DOES solve the problem, checking for wear as suggested above is a good idea.
Team Owner
Joined: Sep 2003
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From: Freedom is never more than one generation away from extinction.
St. Jude '03 thru '24
I ask the questions because the "rear-steer" phenomena is rather typical of many C4's.
Also, I have replaced EVERY rear suspension component in an attempt to remove this problem. Even called the Corvette Guru himself (GK) who didn't know the answer.
After hearing about this event confirms my suspicion that the rear steer problem is all about "rear toe". Its kinda like camel toe only looking at the back.
No, really......
The rear toe is going to change during acceleration and deceleration. There is too much power and torque to not have a little change in toe or camber. So what is the magic number for toe? This I'm trying to determine. The cost of having a shop do three or four aligments is not in my wallet but if we knew what everyones toe settings are then maybe we can deduct the answer.
Also, I have replaced EVERY rear suspension component in an attempt to remove this problem. Even called the Corvette Guru himself (GK) who didn't know the answer.
After hearing about this event confirms my suspicion that the rear steer problem is all about "rear toe". Its kinda like camel toe only looking at the back.
No, really......
The rear toe is going to change during acceleration and deceleration. There is too much power and torque to not have a little change in toe or camber. So what is the magic number for toe? This I'm trying to determine. The cost of having a shop do three or four aligments is not in my wallet but if we knew what everyones toe settings are then maybe we can deduct the answer.
Thread Starter
C3 Corvette Enthusiast
Joined: May 2008
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The torque steer doesn't concern me as much as the "floating" feeling the rear end has on the interstate. I've had the car 1.5 years and thought the old Cooper tires were responsible. The new Falken tires have less of that feeling but it's there and concerning.
Team Owner
Joined: Sep 2003
Posts: 20,179
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From: Freedom is never more than one generation away from extinction.
St. Jude '03 thru '24
There is a big difference in tires and quality/feel.
I suggest you find another Corvette owner and ask to borrow his wheels to help make a better judgement call. Maybe someone with Goodyears or another hiperformance name brand.
Coopers are for the most part bottom end stuff. Falkins were the hot auto-x tires many many years ago. Not any more.......
I suggest you find another Corvette owner and ask to borrow his wheels to help make a better judgement call. Maybe someone with Goodyears or another hiperformance name brand.
Coopers are for the most part bottom end stuff. Falkins were the hot auto-x tires many many years ago. Not any more.......
Safety Car
Joined: Sep 2006
Posts: 4,129
Likes: 1
From: Pasadena CA
I ask the questions because the "rear-steer" phenomena is rather typical of many C4's.
Also, I have replaced EVERY rear suspension component in an attempt to remove this problem. Even called the Corvette Guru himself (GK) who didn't know the answer.
After hearing about this event confirms my suspicion that the rear steer problem is all about "rear toe". Its kinda like camel toe only looking at the back.
No, really......
The rear toe is going to change during acceleration and deceleration. There is too much power and torque to not have a little change in toe or camber. So what is the magic number for toe? This I'm trying to determine. The cost of having a shop do three or four aligments is not in my wallet but if we knew what everyones toe settings are then maybe we can deduct the answer.
Also, I have replaced EVERY rear suspension component in an attempt to remove this problem. Even called the Corvette Guru himself (GK) who didn't know the answer.
After hearing about this event confirms my suspicion that the rear steer problem is all about "rear toe". Its kinda like camel toe only looking at the back.
No, really......
The rear toe is going to change during acceleration and deceleration. There is too much power and torque to not have a little change in toe or camber. So what is the magic number for toe? This I'm trying to determine. The cost of having a shop do three or four aligments is not in my wallet but if we knew what everyones toe settings are then maybe we can deduct the answer.
I also have this problem - it's very subtle and only noticeable on the freeway, but disconcerting. I have got used to it now. I believe that rear heim joints would solve this and that it's a fundamental flaw in C4 rear suspension.The float I don't know about. I also run 32 all the way around. I would say my car only feels light at the back when the tank is nearing empty. Personally I love this - it's more chuckable
When I fill up it feels much heavier at the back.
Team Owner
Joined: Sep 2003
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From: Freedom is never more than one generation away from extinction.
St. Jude '03 thru '24
Sorry guys.
You may not want to hear this but the problem is not worn parts.
Read the first post; his problem started after replacing the tires.
This is an alignment issue, trust me. I've been chasing this for years.
If your vette is not effected by the problem, what ARE your rear suspension settings?
I'm not looking for troubleshooting advice.
We are looking for data.
Thanks.
You may not want to hear this but the problem is not worn parts.
Read the first post; his problem started after replacing the tires.
This is an alignment issue, trust me. I've been chasing this for years.
If your vette is not effected by the problem, what ARE your rear suspension settings?
I'm not looking for troubleshooting advice.
We are looking for data.
Thanks.
Drifting
Joined: Dec 2004
Posts: 1,834
Likes: 2
From: Doylestown PA
When I was auto crossing my 87 I had a mild race alignment.
Rear toe -0.07 right, 0.07 left, total toe 0.00
Rear camber -1.2
Rear thrust angle 0.07
With that alignment the car felt very "planted" at highway speeds. Even with worn shocks.
Since I don't auto cross very much any more I changed the alignment back to stock specifications. The tire wear with the race alignment was killing my tires. Since changing back to stock the Vette still feels good at highway speeds. Nothing gives me the feeling that the car is going to break loose when I change speeds. I drag race my Vette and when I let off the throttle at the finish line I get no noticeable directional change. And that still with worn shocks.
I can't find the print out with the stock specs right now. When I find it I'll post it.
Rear toe -0.07 right, 0.07 left, total toe 0.00
Rear camber -1.2
Rear thrust angle 0.07
With that alignment the car felt very "planted" at highway speeds. Even with worn shocks.
Since I don't auto cross very much any more I changed the alignment back to stock specifications. The tire wear with the race alignment was killing my tires. Since changing back to stock the Vette still feels good at highway speeds. Nothing gives me the feeling that the car is going to break loose when I change speeds. I drag race my Vette and when I let off the throttle at the finish line I get no noticeable directional change. And that still with worn shocks.
I can't find the print out with the stock specs right now. When I find it I'll post it.
Team Owner
Joined: Sep 2003
Posts: 20,179
Likes: 673
From: Freedom is never more than one generation away from extinction.
St. Jude '03 thru '24
Sure thing. Thanks Doug.
I have an 1/8 total toe in on the rear with 1/2 deg neg camber.
It pulls right on acceleration and drifts left when lifting. (C-Beam plates yes)
Most obvious at speed above 50mph.
I have an 1/8 total toe in on the rear with 1/2 deg neg camber.
It pulls right on acceleration and drifts left when lifting. (C-Beam plates yes)
Most obvious at speed above 50mph.
Instructor
Joined: Dec 2005
Posts: 178
Likes: 0
The toe is wrong on one side. You may have 1/8 total but it could all be on one side.
Bushings dont magically degrade when you change tires and tire pressure will probably not make the back feel lose. More camber may help that situation.
Bushings dont magically degrade when you change tires and tire pressure will probably not make the back feel lose. More camber may help that situation.
Team Owner
Joined: Sep 2003
Posts: 20,179
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From: Freedom is never more than one generation away from extinction.
St. Jude '03 thru '24
Burning Brakes
Joined: Oct 2006
Posts: 778
Likes: 0
From: Fort Worth Texas
Could be bushings and such, but yeah, sounds like an alignment issue for sure.
I couldn't be happier with the way my vette drives.
However.......I bought a Miata in January as a dd. That thing almost felt like it was on ice when accelerating on the freeway. One day the interstate was a little wet from a rain shower and the back end decided it wanted to be in the lane next to me (luckily nobody was occupying that space). Hit me all at once that it could be an alignment issue.
I didn't drive it again until after doing a 4 wheel alignment the following weekend. It drives perfectly fine now.
BTW, As of yet, I have had no need for an alignment on the vette. No idea what the settings are.