2ZORNOT2Z

Hi folks,

The thread Yaz started here: https://www.corvetteforum.com/forums...justments.html has a video in it of some snap oversteer at a pretty low speed which made me super nervous with my new Z. I don't want any of that mess as I'm trying to learn the car's idiosyncrasies - I am not pushing it like that guy/gal is on a public road, I need to get some more seat time with the car first. I also saw a ton of posts with tires worn to the cords on the inside by 1500 miles from street use due to the toe being messed up from the factory - this is my main concern since GM will do an alignment for free but won't replace those tires which is much more expensive. So, long story longer... I had them check the alignment so I don't have to replace tires as part of my "free" alignment later, the front toe was out of spec so they fixed it. However, from the sheet they gave me I don't think they even checked the rear caster. The numbers are hard to read on the copy they gave me so here is the info:

Front Left
Camber: -1.0 (before -1.0)
Caster:7.2 (before - 7.2)
Toe: .01 (before .19)

Front Right
Camber: -.08 (before -0.9)
Caster: 7.6 (before 7.6)
Toe: .07 (before 0.16)

Front total:
Cross camber: -0.2 (before -.01)
Cross caster: -0.4 (before -0.04)
Total Toe: 0.08 (before 0.35)

Rear Left:
Camber: -1.3 (before -1.3)
Toe: -.01 (before -0.05)

Rear Right:
Camber: -1.4 (before -1.4)
Toe: 0.0 (before -0.01)

Rear Cross Camber: 0.0 (before 0.01)
Rear Total Toe: -0.01 (before -0.06)
Rear Thrust Angle: 0.00 (before -0.02)

I don't think they looked at the rear caster unfortunately, I see only front caster on the sheet. The car feels planted over seams in the concrete and bumps, tracks straight on the highway at 80, and seems to put power down well. Do I need to go back to have the rear caster checked or am I being too paranoid? Any hints from driving the car that the rear caster is out of whack besides spinning it around a corner? Thanks in advance for the advice!

Mr. Gizmo

Go to pictures on my user profile page. You’ll see the print outs before and after from the dealer alignment I had for street at 500 mile oil change

https://www.corvetteforum.com/forums...and-after.html

2ZORNOT2Z

Thanks @Mr. Gizmo, mine look pretty similar although I have less negative camber than you in the front. Glad I got the toe fixed, that would have worn the front down prematurely. Did you ever end up getting your rear caster checked out? The dealer I went to sells more Corvettes than any other dealer in the area but they didn't check it. There is a highly recommended shop about 30 minutes from me that a lot of the KC folks have used, just not sure if it is something I should be worried about given the car behaves superbly on the road right now. I don't know what I don't know though so that's why I threw it out there. Thanks!

HorsePowerObsessed

Definitely get your rear caster adjusted. It's very important and dealerships typically have no clue how to do it.

rjacobs

If you can feel the rear end wiggle back and forth under hard acceleration when hooked up(3rd gear) then the rear caster is wonky.

Beyond that, IMO, the tech that did your alignment was a bit lazy as they CAN get the measurements perfect, but they didnt, they got it "good enough". Mine was done at a Chevy dealer and the alignment is tight...everything matches side to side. So Chevy dealers CAN get the alignment tight. From the factory my alignment was a disaster.

Bill Dearborn

Your camber numbers look about the same as other cars with the original alignment. Surprised by the amount of front toe in you had although the front tires should still wear well with the reduced toe in (toe in reduces wear from having negative camber, toe out increases wear from having negative camber).

As for rear caster it should be set within GM's specs. However, from what I have seen rear caster will typically fall into those specs when doing a street alignment such as you have as long as the mechanic doesn't mess with the shims behind the UCAs. Rear caster moves out of it's sweet spot when you start pushing rear camber to track settings in the -2.0 or greater range.

I had my car set for a track alignment before I could find a shop that could actually measure rear caster. I ran that way for a year before purchasing the tools myself and finding the rear caster had been set at something like +.4 on the driver's side and -.5 on the passenger's side. I had not noticed any bad handling characteristics while on track with those two readings which are both within GM's 0.0 degrees plus or minus 0.8 degrees specification. Once I was able to measure rear caster I did get it set to +0.7 degrees on each side as DSC recommends.

Since you drive on the street I doubt you need to go on a crusade to get your rear caster measured and set. You are more than likely OK with the settings that you have as rear camber wasn't adjusted and if they didn't touch the camber setting rear caster wouldn't move from whatever the factory set it at.

Bill

Mr. Gizmo

Didn’t have rear caster adjusted. My car was a lot more stable under acceleration with the alignment.

Enjoy your car!

regards,
bill.

2ZORNOT2Z

Thanks, guys. Yes, I thought it was a little sloppy myself when looking at the left and right sides. It does drive well but I don't notice much of a difference from before they aligned it, honestly. I'll have to do a pull in 3rd, rjacobs, and see if I can feel what you describe but I have not felt that doing hard pulls in 2nd once hooked up. Bill, you are saying what I was hoping to hear - that its' probably fine on the rear caster but I was worried about having positive caster on one side and negative on the other since that's really where things seem to get dangerous from what I've read on here. I haven't felt anything squirrely under acceleration really so I'm hoping it's fine where it's at. Thanks again!

rjacobs

If your acceleration doesnt feely squirly in the *** end, then your rear caster is likely fine.

i just said 3rd gear because its easier to hook and put the power down, 2nd works as well.

The factory alignment on my car was really sloppy. I dont know what the rear caster numbers were, but the car was squirrly under hard acceleration. I had the DSC alignment settings done and the car drives well now, I dont feel any odd movement in the rear end on hard acceleration anymore. The dealer tech got everything super tight as well.

I would personally not be happy with the alignment you got...if I had paid for it... but for a free one, you cant really say much because its "in GM's specs" even though its not really tight.

madrob2020

On my ‘16 Z M7 I liked to do WOT runs 1st-3rd with no lift shifts. After the first two times of it trying to dive into the “WEEDS “ I gave up & had the DSC street alignment done paying particular attention to the rear caster. Machine can’t read that measurement. It requires 2 special tools most dealers don’t have but can get thru GM loan a tool program if they are in it. It requires a yearly fee. After alignment, I could do those WOT pulls with dead straight runs laying perfect 20yd marks in 1st & no “wiggle “when banging 2nd/3rd. I’m not telling you that you won’t LOSE it if you try, just that it worked for me. Always try anything like this only on a DESERTED straight/flat road! I have a favorite 1 mile 2 lane with a center turn lane that I line up in. I make 2 runs & then skeedadle!😬

2ZORNOT2Z

Thanks for the advice everyone, I agree it could have been done better but obviously this dealership, or the guy who was on shift that day, only wanted to get it in GM specs. For a free service at least they fixed the toe so I won't have to drop any money on front tires in a couple months. I'm a little frustrated since I asked about the rear caster as my main concern and front toe as second. The SA said, "yeah, we've got all the right tools to check that." Obviously not.

Madrob, I did several 90% or so throttle pulls in 2nd yesterday after getting the tires warm and didn't feel any side to side movement. Actually I was surprised it didn't spin the wheels really, it just laid the power down, man I LOVE this car! Also ran it through a couple round-abouts in 2nd with no other cars around and it felt very stable at around .75G on the meter, accelerating through the last half of the circle. Felt like it was suction-cupped to the pavement. I know that's not a great test but I thought it was decent for the street to give me peace of mind. I think my rear caster is fine for now (hopefully I didn't just jinx it) but since the next alignment is on my dime I'll take it to a specific shop where I know they are familiar with the DSC settings, can check rear caster, and have their own recommendations for the Z06 also.