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First off, I had the wheels off last weekend to replace the brake pads and noticed that the front tires had significantly more wear on the inside edges. So, I instantly knew an alignment was in order.
I'll admit that I'm pretty darn particular and I took my GS to be aligned by a shop that I've been doing business with for over 20 years. I printed out the "PFADT performance street" numbers which I realize after the fact have some generous tolerances. The caster seems like the least important number but it still bugs me that they didnt make it closer to perfect(or at least close to the other side). Of course it's a burden to take the car back and leave it with them. Am I being overly particular?
I'm hoping some folks will help me feel better about this..... but I'm not very optimistic and suspect I'll get encouragement to let the shop know and possibly take it back. Haha.
PFADT Performance Street:
front camber -.7 min -.9 max
front caster 7.5 min 8.5 max
Take it back. Caster is not correct, out of pfadt spec on both sides and in the red on the left. Toe will need to be redone after fixing caster.
Are you sure that's the final numbers?
Hard to believe they would send it out like that unless something is causing it and can't be adjusted to spec.
Usually they will give you a printout of it.
Take it back. Caster is not correct, out of pfadt spec on both sides and in the red on the left. Toe will need to be redone after fixing caster.
Are you sure that's the final numbers?
Hard to believe they would send it out like that unless something is causing it and can't be adjusted to spec.
Usually they will give you a printout of it.
2nd two photos are before. The second two photos are after. So it seems to me the only thing that is out is the caster on one side. I'll edit the original post to make it more clear.
They are not set up to do printouts which is why I asked for a photo. I was curious what it was before they adjustment.... which helps me understand the front tire wear.
2nd two photos are before. The second two photos are after. So it seems to me the only thing that is out is the caster on one side. I'll edit the original post to make it more clear.
They are not set up to do printouts which is why I asked for a photo. I was curious what it was before they adjustment.... which helps me understand the front tire wear.
The middle number is the difference between the two sides, out of spec too. Even if they can't get the caster to the correct spec, they should get the difference as close to zero as possible. This is something you will feel as wandering and unstable at higher speeds.
The middle number is the difference between the two sides, out of spec too. Even if they can't get the caster to the correct spec, they should get the difference as close to zero as possible. This is something you will feel as wandering and unstable at higher speeds.
Ah, OK. I appreciate the explanation. I overlooked the middle number but it did bother me that the two sides were so different.
The before settings had the front caster pretty even, so I'd wonder why it was so off after the alignment. I recently did an alignment on my GS and went for a little more rear camber. As you mention the PFADT specs have a range and I went with the higher end of the range.
I'm old school when it comes to alignment, the tech does the alignment with me in the car, foot on the brake and I center the wheel. It comes from autox days with light weight sports cars. Works well in my vette (not every shop will let you do this.) I take it to performance shops with race experience. I can watch the screen and usually have a greater appreciation of the work that a tech does. When I leave my steering wheel is centered perfectly.
Its a pita for most shops to re-do an alignment and front wheel caster is important. I hope that you are able to get closer to your specs.
The PFADT alignment settings were updated following the information that you are using. The best setting is now exact. I have attached the updated document for your use. I had a local automotive shop perform this on my 2013 GS following new tires and although the alignment tech stated he had to override the machine to do so, he was able to arrive at the exact alignment settings. The tech was also a Corvette enthusiast, so that may have helped to motivate him to get the settings right.
My car tracks straight & true and tire wear is even across the tread pattern on all tires. As an FYI, my original front tires were worn down to the belts on the inside of both tires running on the factory settings.
The PFADT alignment settings were updated following the information that you are using. The best setting is now exact. I have attached the updated document for your use. I had a local automotive shop perform this on my 2013 GS following new tires and although the alignment tech stated he had to override the machine to do so, he was able to arrive at the exact alignment settings. The tech was also a Corvette enthusiast, so that may have helped to motivate him to get the settings right.
My car tracks straight & true and tire wear is even across the tread pattern on all tires. As an FYI, my original front tires were worn down to the belts on the inside of both tires running on the factory settings.
GD
I am going to have my car aligned in the next couple of weeks and have the old PFADT settings document. So the new document you attached removes the gap for tolerance and these are the exact settings that should be used? I assume these settings apply to all C6 models?
I took it back today and got the caster on both sides right around 7 deg. He said he actually moved it a little closer but forgot to snap a pic. He said he likes to have more caster on the one side(the way he had it set) due to the slope in the hwys. He also told me if I didn't like the looseness of the low caster setting that he could move it closer to to upper end. I wish I had the exact numbers but it will be close to this.
2020 Corvette of the Year Finalist (performance mods)
C4 of Year Winner (performance mods) 2019
I've been running this for the last year on my ZR1 and have been very happy with it. Handles just as well on the street (including mountain roads) as when I was running -1.4 camber. Your caster numbers seem a little low, but are probably fine for street. Like you, mine is slightly lower left to right for caster.
I've been running this for the last year on my ZR1 and have been very happy with it. Handles just as well on the street (including mountain roads) as when I was running -1.4 camber. Your caster numbers seem a little low, but are probably fine for street. Like you, mine is slightly lower left to right for caster.
Good to hear. If I understand it correctly, the higher caster would help the car go straight easier(would have more resistance in the steering wheel at speed; the steering would feel heavier.
Originally Posted by Let It Ride
Why is the machine set for a FE-4 suspension? You have a FE-3 with RPO XFA.
Hmmm, I don't know. I know there's a difference between the Z06 and GS but from a suspension and stand standpoint, what would be the difference?
2020 Corvette of the Year Finalist (performance mods)
C4 of Year Winner (performance mods) 2019
Effects of caster:
Increasing the amount of positive caster will increase steering effort and straight line tracking, as well as improve high speed stability and cornering effectiveness. Positive caster also increases tire lean when cornering (almost like having more negative camber) as the steering angle is increased.
C6 steering is boosted enough that it's not going to feel heavy even if you max the caster out.
As to the machine being set for FE-4, that's just going to tell the tech if it's in spec for that car or not. They can still adjust it to any setting.
C6 steering is boosted enough that it's not going to feel heavy even if you max the caster out.
As to the machine being set for FE-4, that's just going to tell the tech if it's in spec for that car or not. They can still adjust it to any setting.
So if you go in with your own specs then you don't even have to tell the machine what kind of car you are aligning? Or in other words tell the machine you have a 2005 Lincoln Town Car just to get the green boxes on the screen and adjust as you see fit?
2020 Corvette of the Year Finalist (performance mods)
C4 of Year Winner (performance mods) 2019
I'd guess you probably have to select some car make/model/year for the machine to allow you to proceed, but from there the tech can set the specs wherever you want. Or maybe there's a way to set it for "custom" and the tech doing the OPs alignment was just to lazy to do that.
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Is this street alignment acceptable?
