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"Rear Caster" adjustments

 
Old 06-07-2019, 08:29 AM
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The Yav
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Default "Rear Caster" adjustments

Gents,
II am due for new tires, I asked the corvette mechanic at the dealership about when doing a 4 wheel alignment can he adjust the rear caster. He said there was not adjustment on his alignment machine. What tool is needed to make rear caster adjustments? Is it a separate digital meter...is there a GM part number for the adjustment tool? How can I describe the process to Mr Goodwrench?
v/r
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Old 06-07-2019, 09:10 AM
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The 2 tools needed are Digital Angle Gauge Adapter (CH-47960-10) & Digital Angle Gauge itself (CH-47960). These tools are not normally kept at dealers due to the very high cost & limited use/need. They are ordered by the dealer thru GM Special Tools website thru the Global Connect Link which has a LOAN TOOL button that is accessed once at the Global Connect Link site. The tools are shipped 2 day delivery to dealer & can be kept for I believe 48 hrs at no cost to YOU or dealer, then shipped back. So they should get tool ordered & your appointment co-ordinated to meet these requirements. Just double checked my info on Google. The dealer has to be in the tool loan subscription program (annual fee) & the tool can be kept 5 days.

Last edited by madrob2020; 06-07-2019 at 09:19 AM.
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Old 06-07-2019, 09:32 AM
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If the "corvette mechanic" did not know of the special tools needed for setting rear caster I would think twice about having him do the rear alignment. Rear caster is important handling performance and often found to be out of spec from the factory. I would find someone who has done it before and appreciates how important it is to set it correctly.
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Old 06-07-2019, 10:55 AM
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GM manual
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File Type: pdf
C7 4 Wheel Alignment.pdf (1.36 MB, 25 views)
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Old 06-07-2019, 12:45 PM
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Originally Posted by ZO6 Guy View Post
If the "corvette mechanic" did not know of the special tools needed for setting rear caster I would think twice about having him do the rear alignment. Rear caster is important handling performance and often found to be out of spec from the factory. I would find someone who has done it before and appreciates how important it is to set it correctly.

THIS!!! I was told the same thing AFTER they did my alignment and it was so out of whack afterwards that the car felt EXTREMELY unstable over bumps. I ended up taking it to TPC in Maryland to get the alignment done correctly and they said my rear drivers side caster was +1.7 degrees and the passenger side rear caster was -1 degree. Basically, it was WAYY out. If you have the same luck I did, you won't find a dealership that can do the alignment properly. I called 10 dealerships and NONE of them had the tool or even knew what I was talking about (2 of the dealerships were SPECIFICALLY Corvette dealerships). Check out the video here if you want to hear/see more:

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Old 06-07-2019, 01:34 PM
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The cars are delivered from the factory with the alignments way out of wack and not symmetrical. MANY owners have confirmed they do a **** job on aligning before shipping. For instance, the car/factory "acceptable" specs for discussion purposes for rear caster might be -1.0 degrees to +1.0 degrees. It's not unusual for cars to come with one side positive and one side negative. They get "green" lights as they are within range even though they're cattywhompous left to right. Here's an example of the VERY dangerous snap oversteer you can experience when you have a factory alignment with one side positive and the other side negative. The bad event depicted below was NOT driver error. The snap oversteer occurred at about 64 mph on a road with a posted speed limit of 55 mph! After the incident and with the alignment corrected this same car navigated the same turn at 80+ mph without any issues or drama.


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Old 06-07-2019, 02:06 PM
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Originally Posted by rikhek View Post
The cars are delivered from the factory with the alignments way out of wack and not symmetrical. MANY owners have confirmed they do a **** job on aligning before shipping. For instance, the car/factory "acceptable" specs for discussion purposes for rear caster might be -1.0 degrees to +1.0 degrees. It's not unusual for cars to come with one side positive and one side negative. They get "green" lights as they are within range even though they're cattywhompous left to right. Here's an example of the VERY dangerous snap oversteer you can experience when you have a factory alignment with one side positive and the other side negative. The bad event depicted below was NOT driver error. The snap oversteer occurred at about 64 mph on a road with a posted speed limit of 55 mph! After the incident and with the alignment corrected this same car navigated the same turn at 80+ mph without any issues or drama.

http://youtu.be/1nUzvzH5AjU

That's crazy! I know with how my car felt, over bumps especially, it was definitely unsafe. With a proper alignment it feels completely different. More planted and zero loose rear end feeling.
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Old 06-08-2019, 07:42 PM
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damn! I would have definitely been cursing and would have gotten out of the car and looked around before I drove off.
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Old 06-08-2019, 10:47 PM
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Originally Posted by RegnaR View Post
damn! I would have definitely been cursing and would have gotten out of the car and looked around before I drove off.

lol I thought the same thing. He is oddly silent in the video, there would have had some more colorful language if it had happened to me..
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Old 06-09-2019, 04:43 PM
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Rick I had a similar incident with my car before I got the rear caster set correctly. I made a left 120 degree turn to the left going about 20 and the rear end came all the way around. Weather was also a factor because it was around 35 degrees outside. I was going slow enough that I stayed in the road and in my lane. These cars are totally different animals if the alignment is out.
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Old 06-09-2019, 10:13 PM
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Originally Posted by badhabit_wb View Post
Rick I had a similar incident with my car before I got the rear caster set correctly. I made a left 120 degree turn to the left going about 20 and the rear end came all the way around. Weather was also a factor because it was around 35 degrees outside. I was going slow enough that I stayed in the road and in my lane. These cars are totally different animals if the alignment is out.
Very true. It's unreal how much more planted the car feels with the alignment set correctly.
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Old 06-10-2019, 06:23 AM
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I was cringing on the yellow car video in the first 2 curves he went around...

I feel like he had the nannies off. He was going faster in the curves than he was the straights.

His lines were strange, it's like he was trying to get it to spin the way he would steer and accelerate.

It's scary that people who don't know how to drive go out and buy these cars.

There needs to be a different class license required to own a car over 500hp, and then another for 700hp and so on...

otherwise, all fast cars will be made illegal once enough of these people who can't drive kill enough people... the fast car will be labeled as the problem

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Old 06-10-2019, 10:17 AM
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Originally Posted by bbbvettes.com View Post
I was cringing on the yellow car video in the first 2 curves he went around...

I feel like he had the nannies off. He was going faster in the curves than he was the straights.

His lines were strange, it's like he was trying to get it to spin the way he would steer and accelerate.

It's scary that people who don't know how to drive go out and buy these cars.

There needs to be a different class license required to own a car over 500hp, and then another for 700hp and so on...

otherwise, all fast cars will be made illegal once enough of these people who can't drive kill enough people... the fast car will be labeled as the problem
Rick is a lot better driver than most on the forums. His car just broke because of the alignment. On a dry road at that speed it should have never been a problem. You should check out some of his track times. No way is he a bad driver!
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Old 06-10-2019, 01:38 PM
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I did not realize we knew the guy, I thought it was a video off the net someone found.

I would say he is used to having warmer stickier tires then, to contend with such driving, and also, the rear caster was off... which was the original point, I get it.
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Old 06-10-2019, 02:08 PM
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When mine did it I was taking my son to school. If someone had told me the rear end would come around like that, without acceleration, at 20mph or so I would have called them a liar. I caught it but it's because I was going so slow. That's when I decided to learn to do my own alignments.
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Old 06-11-2019, 04:06 PM
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That video and badhabit's story make me extremely nervous with my new Z! I've not noticed any instability around corners but also am not pressing it with a new car either. Do most Chevy dealers have issues checking the alignment to see if it's out of whack and just can't adjust it or can they neither check the rear caster nor adjust it? I'll ask about having my alignment checked at least when I go for the 500 mile oil change. This is great information!
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Old 06-11-2019, 04:16 PM
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Originally Posted by 2ZORNOT2Z View Post
That video and badhabit's story make me extremely nervous with my new Z! I've not noticed any instability around corners but also am not pressing it with a new car either. Do most Chevy dealers have issues checking the alignment to see if it's out of whack and just can't adjust it or can they neither check the rear caster nor adjust it? I'll ask about having my alignment checked at least when I go for the 500 mile oil change. This is great information!
I actually made a video of my trip to DSC in Maryland and the biggest reason I made the trip? To get an alignment done CORRECTLY. The previous place to do the alignment on my car was a GM dealership and they really messed it up. A good quality alignment shop that can adjust the rear caster is definitely important...

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Old 06-11-2019, 04:38 PM
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Originally Posted by JAYNO20 View Post
I actually made a video of my trip to DSC in Maryland and the biggest reason I made the trip? To get an alignment done CORRECTLY. The previous place to do the alignment on my car was a GM dealership and they really messed it up. A good quality alignment shop that can adjust the rear caster is definitely important...

https://www.youtube.com/watch?v=qjdt4O4JCiE&t=120s
Thanks for the info, wish I was in Maryland, those guys sound excellent! Any KC area people have a good alignment shop recommendation?
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