Weird handling issue
Thread Starter
8th Gear
Joined: Nov 2022
Posts: 8
Likes: 1
From: Georgia
Weird handling issue
My vette spent three months in the shop having the front bumper and passenger fender repaired after hitting a deer. It was fully drivable, and still felt just as solid as ever when I handed it over to be repaired. As part of the repairs, the repair guy mentioned that he did a full four-wheel alignment. When I drove the car home, it felt different. When I drive over an odd bump in the road (an expansion joint, for example), the car feels "wobbly" in the back. Maybe a bit floaty is a better description. When I got home I took a look at the rear wheels and noticed that the whole axle seems off, like it is twisted a couple degrees from perpendicular. The rear passenger side tire is way closer to the front-side fender wall than the driver side, to the point that where you can see that the fender wall is being eaten by the tire when going over bumps. It is easy to conclude that the floaty feeling going over lumps in the road is caused by one rear tire hitting it just oh-so-slightly before the second one.
Could this be the result of the alignment process, or is there something else going on?
Could this be the result of the alignment process, or is there something else going on?
Race Director
Joined: Mar 2010
Posts: 16,012
Likes: 828
My vette spent three months in the shop having the front bumper and passenger fender repaired after hitting a deer. It was fully drivable, and still felt just as solid as ever when I handed it over to be repaired. As part of the repairs, the repair guy mentioned that he did a full four-wheel alignment. When I drove the car home, it felt different. When I drive over an odd bump in the road (an expansion joint, for example), the car feels "wobbly" in the back. Maybe a bit floaty is a better description. When I got home I took a look at the rear wheels and noticed that the whole axle seems off, like it is twisted a couple degrees from perpendicular. The rear passenger side tire is way closer to the front-side fender wall than the driver side, to the point that where you can see that the fender wall is being eaten by the tire when going over bumps. It is easy to conclude that the floaty feeling going over lumps in the road is caused by one rear tire hitting it just oh-so-slightly before the second one.
Could this be the result of the alignment process, or is there something else going on?
Could this be the result of the alignment process, or is there something else going on?
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Tech Contributor
Joined: Oct 1999
Posts: 41,058
Likes: 9,820
From: Charlotte, NC (formerly Endicott, NY)
My vette spent three months in the shop having the front bumper and passenger fender repaired after hitting a deer. It was fully drivable, and still felt just as solid as ever when I handed it over to be repaired. As part of the repairs, the repair guy mentioned that he did a full four-wheel alignment. When I drove the car home, it felt different. When I drive over an odd bump in the road (an expansion joint, for example), the car feels "wobbly" in the back. Maybe a bit floaty is a better description. When I got home I took a look at the rear wheels and noticed that the whole axle seems off, like it is twisted a couple degrees from perpendicular. The rear passenger side tire is way closer to the front-side fender wall than the driver side, to the point that where you can see that the fender wall is being eaten by the tire when going over bumps. It is easy to conclude that the floaty feeling going over lumps in the road is caused by one rear tire hitting it just oh-so-slightly before the second one.
Could this be the result of the alignment process, or is there something else going on?
Could this be the result of the alignment process, or is there something else going on?
For tire mileage set the following:
Front Left Camber set to -0.6, Right Camber set to -0.6 set Cross Camber as close to 0 as possible. Front Left and Right Caster should be set to +7.5 with 0 Cross Caster. Set front toe to 0.0 degrees or maybe a shade toed in at 0.02 deg total toe.
Rear Left Camber set to -0.9 Right Camber set to -0.9 set Cross Camber as close to 0 as possible. Rear Left Caster set to 0.0 +/- 0.02 deg Right Caster set to 0.0 +/- 0.02 deg. Get the cross-caster as close to 0 as possible. Set the rear toe to 0.0 degrees or maybe 0.01 total deg and the thrust angle to 0.0 degrees.
Bill
Burning Brakes
Joined: Jun 2015
Posts: 1,157
Likes: 522
From: Central Jersey
For tire mileage set the following:
Front Left Camber set to -0.6, Right Camber set to -0.6 set Cross Camber as close to 0 as possible. Front Left and Right Caster should be set to +7.5 with 0 Cross Caster. Set front toe to 0.0 degrees or maybe a shade toed in at 0.02 deg total toe.
Rear Left Camber set to -0.9 Right Camber set to -0.9 set Cross Camber as close to 0 as possible. Rear Left Caster set to 0.0 +/- 0.02 deg Right Caster set to 0.0 +/- 0.02 deg. Get the cross-caster as close to 0 as possible. Set the rear toe to 0.0 degrees or maybe 0.01 total deg and the thrust angle to 0.0 degrees.
Bill
Front Left Camber set to -0.6, Right Camber set to -0.6 set Cross Camber as close to 0 as possible. Front Left and Right Caster should be set to +7.5 with 0 Cross Caster. Set front toe to 0.0 degrees or maybe a shade toed in at 0.02 deg total toe.
Rear Left Camber set to -0.9 Right Camber set to -0.9 set Cross Camber as close to 0 as possible. Rear Left Caster set to 0.0 +/- 0.02 deg Right Caster set to 0.0 +/- 0.02 deg. Get the cross-caster as close to 0 as possible. Set the rear toe to 0.0 degrees or maybe 0.01 total deg and the thrust angle to 0.0 degrees.
Bill
At the front I'm running -1.2 camber with 0.0 toe and max caster.
At the rear camber is the same at -1.2 with very small toe in for stability and rear caster set at +0.7. It feels comfortable to me on street and occasional track.
New DSC spec calls for rear castor at 0.0, same as GM spec, but also indicates its for use with their DSC controller. I am stock.
Much more than-1.2 camber would increase tire wear on the street and some rear toe-in, seems to me, has always been the rule for IRS cars.
Question for me is where should i have the shop set the rear caster? +0.7 original spec or +0.0 latest spec?
I respect your opinion/experience and appreciate the knowledge you bring to this forum
Thread Starter
8th Gear
Joined: Nov 2022
Posts: 8
Likes: 1
From: Georgia
Update: I took it to another alignment shop and the consensus is that the rear is aligned dead-on. Everyone is stumped. There is nothing visibly wrong with the cradle or control arms. We spent three hours under it with a tape measure and flashlights to no avail. I guess the next step is to start taking it all apart to see if there's anything cracked or bent that we can't see with everything put together.
Edit: Just saw the camber/caster comments above. I'll make sure to take these numbers back. Thank you.
Edit: Just saw the camber/caster comments above. I'll make sure to take these numbers back. Thank you.
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Thread Starter
8th Gear
Joined: Nov 2022
Posts: 8
Likes: 1
From: Georgia
Update: Problem solved. Took it to a different alignment shop that had a guy with 40 years experience. He fixed it right up. Didn't cost me a penny, either, as the body shop guy felt so bad about the first screw up. Installed new fender wall liners, too, for free.
Heel & Toe
Joined: Jan 2023
Posts: 20
Likes: 9
From: DFW, Texas
Originally Posted by Stingradius;[url=tel:1606344800
1606344800[/url]]Update: Problem solved. Took it to a different alignment shop that had a guy with 40 years experience. He fixed it right up. Didn't cost me a penny, either, as the body shop guy felt so bad about the first screw up. Installed new fender wall liners, too, for free.
Drifting
Joined: Sep 2019
Posts: 1,355
Likes: 635
From: St. Louis
Question for Bill... why do you recommend -0.9 deg camber in the rear and less in the front? My experience has always been that you need a bit more camber in front than rear because front tires need to wear the outer edges due to steering. This is for street driven cars, not track driving.