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Anyone ever crossweight and balance check a Z06 from the factory?
You often hear the statements about the cars shipped at a higher ride height, then dealer does some lowering for pre-delivery. Then some owners don't want it, etc. It just led me to wonder how consistent these cars come out of the factory and if they'd benefit immediately from an actual chassis setup with scales/alignment/etc. I'm betting they would.
I checked some of that. However, I didn't check the cross weight since I didn't have the tools. Front alignment check showed I had -1.0 deg camber on both front wheels with a 1/16 toe in setting. Rear alignment showed I had -1.2 deg camber on both rear wheels with a 1/32 toe out setting.
Z07 front splitter was 5.5 inches off the ground on both the left and right side of the car which is almost high enough because even on my almost level driveway it scrapes if I don't turn the wheel sharply as the front wheels enter the curb dip. Having been under the car I can tell you don't want that carbon fiber splitter rubbing on the ground too many times. It really gets deeply scratched rubbing over concrete.
The height of the side skirts varies from front to rear and from side to side.
Left side front is 5 in while left side rear is 6 5/16 in
Right side front is 5.25 in while right side rear is 6 3/8 in.
Yes I weighed mine bone stock. I tried to dig up a photo of the scale for you, but could not find it. It was within 1% on the cross-weight. I set it perfectly with my weight in the car using the stock lowering bolts. It required very little adjustment to balance perfectly. The alignment was slightly off, but I didn't check it until several thousand miles were on the car. It was not equal side to side on the toe or camber.
I do not believe my dealer did any lowering at delivery. I doubt most people would notice any immediate improvement with a corner balance at delivery, unless they were seasoned track guys or autocrossers. But the alignment change will definitely be noticed, even in street driving.
Checked mine after lowering. All 4 corners were within 30#, near perfect 50/50 weight distribution. Total weight was 3,465#with 3/4 tank of gas (Stage 1 car) and maybe 15# of sound deadening and block-it pad.
My experience with Corvettes starting with the C4 up through the C6 is that the cross weights are pretty good, but the alignment from the factory might be horrible. My first Vette was nearly undriveable, even after the dealer grudgingly performed an alignment under warranty. It took a visit to a Corvette specialty shop to get the handling that I was expecting.
I had mine done today. I don't know how bad it was at first (sent the question), but here's what we came up with. It's set up a bit heavy on the driver side (mostly because I am a bit heavy!!!!) so hopefully I can lose some weight and even it out side to side.
I had mine done today. I don't know how bad it was at first (sent the question), but here's what we came up with. It's set up a bit heavy on the driver side (mostly because I am a bit heavy!!!!) so hopefully I can lose some weight and even it out side to side.
This doesn't look to bad to me. You could raise the right side of the car incrementally using the spring bolts to shift the weight to the right, or lower the left side.
I had mine done today. I don't know how bad it was at first (sent the question), but here's what we came up with. It's set up a bit heavy on the driver side (mostly because I am a bit heavy!!!!) so hopefully I can lose some weight and even it out side to side.
Why -.8 on caster Vs GM's recommended 0 degrees? Also, did they have to remove shims from behind the UCAs to get the camber settings and toe adjustments?
Bill
Last edited by Bill Dearborn; 03-26-2016 at 07:01 PM.
Why -.8 on caster Vs GM's recommended 0 degrees? Also, did they have to remove shims from behind the UCAs to get the camber settings and toe adjustments?
Bill
The toe curve is much better at -0.8 than at 0. At 0 the rear goes in to toe out under compression.
I removed my washers last year for that reason. I've been told you can get to 2.1 in front and 1.6 in the rear without removing washers. Mine are gone though.
Very nice to see that GM has the true outgoing car fairly well set up. I imagine they've got the factory suspension hardware located through a gauge to know exactly where to index everything. I'm surprised to see the results here as good as they are. I expect Porsche or someone to really go that extra mile to insure the car is balanced 100% properly, but with GM I assumed maybe some slack would exist.
Just to be clear, my numbers were not factory numbers. These are post-balance numbers. I'm trying to find out how far I was from the factory, but we probably won't know because we lowered it a bit first and then raised it to get weights correct.
Just to be clear, my numbers were not factory numbers. These are post-balance numbers. I'm trying to find out how far I was from the factory, but we probably won't know because we lowered it a bit first and then raised it to get weights correct.
Adam, your car as supplied to me was 51.8% LR-RF , and 48.2% RR-LF so it was 3.6% out of balance total cross. Which is a fair amount to be out. The gentleman that posted earlier his #'s was much further off.....and when you are talking about small percentages of 3800lbs, that actual number is a fair amount. Actually your numbers were after I lowered the car, so not really sure what it was originally, but I am sure it was close to the stated #'s as I lowered it equally per axle.
As far as shifting weight left to right, you are unable to do this with ride height adjustment in contrast to what was previously said. The only way to correct left-right balance would be to lose weight on the left, or gain weight on the right.
The toe curve is much better at -0.8 than at 0. At 0 the rear goes in to toe out under compression.
I removed my washers last year for that reason. I've been told you can get to 2.1 in front and 1.6 in the rear without removing washers. Mine are gone though.
So when you are quoting -.08 caster in the rear, that would put the top of the spindle further forward?
Just trying to make sure that I understand which way + and - caster are in this scenario.
You do a bump measurement throughout the range of travel
I am assuming.
So when you are quoting -.08 caster in the rear, that would put the top of the spindle further forward?
Just trying to make sure that I understand which way + and - caster are in this scenario.
You do a bump measurement throughout the range of travel
I am assuming.
Yup so lower ball joint forward of the upper ball joint. I haven't done the test but someone I trust very much has and provided the recommendation after a lot of tests and track time.
Yup so lower ball joint forward of the upper ball joint. I haven't done the test but someone I trust very much has and provided the recommendation after a lot of tests and track time.
Ok so now I'm confused. If the lower ball joint is forward of the upper ball joint as it is in the front of the car, I've always understood that to be positive caster. Negative would be where the upper ball joint is forward of the lower according to all that I have seen.
Of course there is always the argument about which way toe in and out is represented by +or - as well.
Ok so now I'm confused. If the lower ball joint is forward of the upper ball joint as it is in the front of the car, I've always understood that to be positive caster. Negative would be where the upper ball joint is forward of the lower according to all that I have seen.
Of course there is always the argument about which way toe in and out is represented by +or - as well.
Yes you are correct, positive rear caster. Sorry for the delay, I wanted to confirm prior to responding. Lower ball joint forward of the upper. Makes a big difference in bump steer.
My buddy is at VIR with this setup today and says the car is handling terrific.
Yes you are correct, positive rear caster. Sorry for the delay, I wanted to confirm prior to responding. Lower ball joint forward of the upper. Makes a big difference in bump steer.
My buddy is at VIR with this setup today and says the car is handling terrific.
Schaibaa, may I beat this horse a bit more? I'm still not clear between your alignment sheet and the responses from you and Fmcokc. I think you are saying the rear of your car is set up with positive 0.8 degrees caster, which has the lower ball joint more towards the front of the car than the upper, right?
Schaibaa, may I beat this horse a bit more? I'm still not clear between your alignment sheet and the responses from you and Fmcokc. I think you are saying the rear of your car is set up with positive 0.8 degrees caster, which has the lower ball joint more towards the front of the car than the upper, right?
His sheet says negative caster but his comments about the lower bj being forward of the upper bj indicate positive caster. Accepting his answer to my question about the toe curve being better at the .8 setting the only issue we have is which direction do we move the lower bj.
For most of us that is presently a moot question since we either don't have the tools to measure the rear caster ourselves or the dealers we can get to don't have them. There is even less liklihood of finding an independent alignment shop with the required equipment.
I have an adapter on order so I can use my Longacre digital caster camber gauge to measure the caster but it fries me to no end that if I want a dealership to adjust the rear caster I have to provide them the tools to do the job.
I really don't want to tow my car for 8 hours to have Raft Racer do the setup but my son who lives in Michigan is talking about the two of use doing a track event at Mid Ohio so maybe it might work out.
Bill
Last edited by Bill Dearborn; 04-08-2016 at 01:14 PM.
03-25-2016, 11:01 AM
Anyone ever crossweight and balance check a Z06 from the factory?
