I have read that rear wheel caster is important on the Z06 and many times factory setting is off. I am taking my 2017 non-Z07 in for first alignment today. New tires, 29,000m. I asked the alignment shop if they had the tools and know-how to adjust rear caster on my vette and they told me yes. Based on what I have read, I am a bit skeptical. Two questions:
1. Is the only way to correctly and precisely adjust the rear caster is by using the tool (either GM or similarly fabricated) that attaches to the control arm using the two pins for alignment or is there another tool/way to do the caster measurement correctly?
2. When I get to the shop, what do I ask the technician or watch for to verify that the caster measurement is being done correctly?

Thanks for any advice.
John

 

Very few shops have the correct tools to set the C7 Caster because very few cars on the road have an adjustable rear Caster. It isn't rocket science, you can build your own tool like I did for a few bucks. There are several threads on the forum about this.

Enjoy the ride.

 

https://www.corvetteforum.com/forums...er-tool-2.html

https://www.corvetteforum.com/forums...sues-rant.html

 

First thing is most of the people that answer the phone in a shop really don't know. When they hear the word caster they automatically think front caster as all the other cars they work on only have front caster. So you need to make sure they know you are talking about rear caster and that means talking to them face to face through masks while watching their eyes. If they state their machine measures rear caster they have no clue. If their eyes look confused when you emphasize rear caster, they have no clue. If they say yes, we have the adapter and a gauge to measure rear caster they know what they are talking about.

GM only defines the adapter as an essential tool. They let the shops decide what gauge to use, although the GM gauge is recommended.

A couple of 3/16 carriage style bolts with the threaded ends cut off will fit in the holes and let somebody put an angle gauge across the two bolts to measure rear caster. Some people have placed the thin edges of their smart phones against the two bolts and used an angle app to measure the caster angle.

If they do adjust the rear caster have them set it at 0 on each side. GM has a plus or minus 0.8 degree tolerance on the rear caster with no cross caster requirement. Theoretically you could have the left rear wheel caster set at +0.8 degrees and the right rear wheel set -0.8 degrees and rear caster would be considered good. I suspect with most street alignments rear caster easily falls into the +0.4 to -0.4 degree range. If you have a gauge that only has plus or minus 0.2 degrees of accuracy that means you aren't going to get much better of an adjustment. As Jim Mero said in another forum post rear caster was put in place so they could keep the caster as close to zero as possible through a range of rear camber adjustments.

Bill

Bill

 

Thanks for the reply. As I expected, and as Bill wisely stated, when I got to the shop and asked the alignment technician if he could adjust rear caster, his first words were "That car does not have adjustable rear caster." This was the same tech the owner (for 35 years) asked when I called and explicitly asked if they could measure and adjust rear caster on a 2017 Corvette Z06. Needless to say, before I left I had a short discussion with the owner over this SNAFU.

I asked the tech if he could do the caster adjustment if I brought the tools needed and he said yes. I will make a tool from bolts and square steel tubing and buy an angle gauge with mag base. Will try to find one with +/-0.1 degree accuracy. Wixey WR3200 Type 1 is not available, but WR300 Type 2 is. Anyone have any recommendations for angle gauge?

 

You do not need the adapter to measure rear caster. There is an edge machined into the knuckle arm that you can place a digital torpedo level up against and take your measurements. Of course, the torpedo level will not stay attached to the suspension, so you have to adjust and re-measure until you get it right. But that is pretty much how suspension alignment is done anyway.

I suspect the tech will hate you before he gets it right. As you adjust camber, the caster changes and vice versa. So he will have to keep checking back and forth until he gets both where they need to be. Way more difficult than just setting camber like the old days.

 

Since you're in CA, the absolute "go to" place is West End Alignment....18008 S Vermont Ave, Gardena, CA 90248

A bit pricey but worth every penny. I use him for track alignments on my 2019 as do many other local Corvette track rats. He'll set the alignment dead on to your specs or he can recommend specs based on how you drive the car...street, track, mix, auto-x, etc. This is the only shop I have confidence in regarding rear caster.

 

Slightly off subject but since we’re talking alignments. Can you still get one free alignment on a new C7 Corvettte? Any restrictions?

 

I asked my dealer to check the alignment went I went in for my first oil change at 500 miles. I stated that it feels like it is "possibly" pulling to the left. They checked it out as within the warranty period at no charge. It was fine by the way.
So I am assuming that if you have them check it out soon after you buy the car it is free. Don't know if that goes up to 36,000 miles.

 

Whenever someone says "That car does not have adjustable rear caster" that is your cue to leave. Do NOT let that person adjust your rear caster, take it to someone who knows the car.

 

They need this tool and a angle gauge !!!

 

Thanks for the info. I did that for the C6. Then I did a “by the way, while he is doing the alignment can he take the GrandSport aggressive alignment out of it”. And they did. Didn’t know if they still did that or not. That’s what I want to do with the new GS.

 

Got appointment with West End Alignment for next week. Thanks so much for the referral. A bit pricey at $180, but the tools to do the rear caster would have cost me close to $100 and I would need those for the local guy to do rear caster, plus hope he knows what he is doing and doesn't make things worse.

 

I'm not sure why people seem to think you can just rig something up and expect quality results. Gm designed a tool to make this adjustment for a reason. The window your after for "gm specs" is literally 3 tenths of ONE degree. Iv talked to people who gave run 0 all the way up to positive one and they have said a small amount of adjustment makes a huge difference on how the car acts.

 

Because this:
Mona Lisa: If you will look in the manual, you will see that this particular model faucet requires a range of 10-16 foot pounds of torque. I routinely twist the maximum allowable torquage.
Vinny: How can you be sure you used 16 foot pounds of torque?
Mona Lisa: Because I used a Craftsman model 1019 Laboratory edition, signature series torque wrench. The kind used by Cal Tech High Energy physicists, and NASA engineers.
Vinny: In that case, how can you be sure THAT'S accurate?
Mona Lisa: Because a split second before the torque wrench was applied to the faucet handle, it had been calibrated by top members of the state and federal Departments of Weights and Measures, to be dead-on ***** accurate. Here's the certificate of validation!
Vinny: "Dead-on ***** accurate"?
Mona Lisa: It's an industry term.

 

If your dealer is like mine, they charge extra for a "custom alignment" which is what they call it if they have to go find the rear caster equipment. I asked my dealer how much for an alignment including rear caster and he said $350 and it would take them half a day. I took it to an indy shop that does a lot of cars on Friday to race on Saturday and then sets them back Monday for their owners and he took 1 hour, charged me $150 but spend 30 minutes beforehand talking with me about how I use the car, how would I like the car to perform, etc... then told me how he'd set it up. It pretty much matched the DSC specs so I knew I was in the right place. He got it right on the mark too. I don't think $180 is a high price at all for a quality alignment, your dealer will charge you double that and still get it wrong most likely.

 

I have just gone through this as a DIY, making my own caster tool. All I will say is, if you can get it done for $180 by a guy who cares, do it. I have to do mine on a ramp made of 2x10s, and using a floor jack to take the weight off the wheels to make the adjustments. I have, on other cars, had bad luck relying on the eccentrics when the car has it's weight on the wheels. Getting the rear caster right along w/ the camber, getting both sides equal, required jacking the rear of the car up, adjust, drop it down and then roll it back and forth to settle the suspension, measure, 10 cycles. And then I did the toe. And the next day I did the front.

 

I did the same thing and had him put it in a street alignment bias. Brilliant minds think alike.

 

Craig,
It sounds like you did it right! It is a real pain to get it perfect, which is why most shops will get it "close enough" and call it a day.

I have a suggestion for you to make it quicker next time. Rather than making some adjustments blind and then lowering / settling the car to see if you may have gotten it close, if you have a digital level, you can take original measurements and figure out how much each alignment axis needs to move. Then, with the car jacked up, you can use your digital level to measure and adjust each axis by the amount it needs to move. What I mean by that is if you determine you need 0.5 degrees more camber and 0.2 degrees more caster (for example), once you have the car jacked up, measure and reference the hanging values and adjust them by that much. The angles will be way off when you have the suspension hanging, but you go from there and adjust those by the amount you have determined you need from your sitting on the ground measurements.

That won't be perfect because the suspension is hanging down, but it gets it pretty close and then you can lower the car and settle the suspension and measure how close you came. Probably one more adjustment cycle and you will have it where you want it. It might take three cycles total to get it perfect, unless you do what I did and go the wrong way when it is up in the air..... It is easy to get confused with all the measurements so take good notes for each step.

 

West End Alignment is not a dealer. They are a shop whose primary business is alignments....ie they're not a tire shop or a general repair shop that does alignments on the side. They are very popular with local racers and track rates and it is not unusual to see high-end cars...Ferrari, McClaren, etc... in their shop. As I mentioned above, they'll align to your specs or can recommend specs. Same price. If desired, they'll let you sit in the car (or they can simulate your weight) during the alignment. After the alignment, they have the driver take the car for test drive. If the car doesn't feel right or the steering wheel is not centered to the customer's expectations, they'll adjust and have the driver retest until it is right. They charge a flat rate. If they get the alignment done in 15 minutes, good for them. If it takes 3 hours, it is what it is. At my last alignment, we spent about 90 minutes.