Sorry to beat a dead horse with another alignment thread but I'm curious what you all think about this alignment that I just received.

They are a shop that specializes in road racing and have great reviews, so I gave them PFADT specs and told them to do something between street and mild track specs. They talked me into the toe and I'm not sure how I feel about it. They said that amount will help it track straight without wearing the tires. I'm not an alignment expert nor did I want to debate a shop I'm trying to build rapport with.

For example, does ".03in" for the rear toe mean it's positive .03 inches, is it .03mm inward toe, or something else?

Car felt a lot more stable on the way home, I was experiencing issues with the front feeling washy before the alignment and new tie rod ends, but it had also just rained so I couldn't push it very far.

 

It means toe-in on that side. The sum of the rear toe measurements is the total rear toe. 0.03" + 0.03" = 0.06". Note that for toe, Pfadt uses the opposite sign convention than almost everyone else. Pfadt denotes toe-in with negative numbers, but the prevailing convention is to denote toe-in with positive numbers.

 

Looks good to me! You could try a little more toe in for the rear and or a little toe out for the front.

 

Awesome, thanks for giving me confidence in the alignment and for the info about the way PFADT shows their toe specs.

 

Looks OK to me too!
A little more toe in at the rear will help with stability, if you feel like it needs it.
From memory, spec on the F toe is somewhere around zero, so .01 is OK either in or out.
I usually use just a little more in...
That reading is probably in inches. Other readings in degrees are marked as such, and .01 mm is probably too small for the machine to measure.

Some people will recommend a small amount of toe out for track cars, to help with turn-in.
If it's a dual purpose car, I always recommend against that.
The minimal gain on the track with be paid for with a ridiculous amount of inner edge wear on the street.
If it is dual purpose, you can get away with a lot more negative camber. Tires are more forgiving of that than they are of toe.

 

Yeah this is a street car so I'd rather err on the side of that than the track.

I noticed today when turning a little aggressively onto an on-ramp that the car wanted to slide wide. Almost like oversteer but not something I've really experienced or could explain. My tires were warm and up to 37 psi at that point so I think I just need to let a few psi out. Tires are good. It oversteered on the way home from the alignment too but I chocked that up to the road being damp. Will keep an eye on it and be careful until in used to it again.

 

So after driving this for the past week I am actually a little scared of the alignment, the rear end really wants to let go in turns and it does so very suddenly.

I've had the car for over 2 years and never had this issue so I am thinking it's alignment related.

Was my alignment before too tame? Is that just the nature of the C6 with these specs or is something wrong?

I setup an appointment to go back and re-check the specs, but they can't get me in until July 31st so until then I just have to be careful. Totally killed the fun I've been having with the car because I'm afraid it's going to slide out from under me. I am an avid moto rider and have done track days, so I know not to be aggressive with applying or letting off of the throttle or brake in turns, but this still happens, which is what makes me so nervous with it.

 

I was going to say it might tend towards over steer but there are so many parts combo. I have run an alignment like that and found it to be pretty balanced. If I were you I would get an adjustable rear sway bar or new rear tires or try different air pressure. I’m not sure the age type or condition of the tires.

 

Crawl under the back of the car and add two flats of tow-in to the rear and see how it responds. You should be able to do this with the car on the ground.

 

I measured the tire PSI with an analog gauge instead of using the DIC. Fronts and rears both read 37. I dropped the fronts to 35 and the rears to 32, so we'll start there and see how that feels tomorrow.

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​​​​​​Is 3mm of toe in too much for a street car? I just watched a series this guy made about adjusting suspension and he says at about 9:50 in this video that our cars love to toe out and adding toe in helps prevent the rear end from kicking out in tight turns. That's exactly what my car is doing... Kicking out in tight turns.



If the machine is reading .03" for my car, that's only .762mm, so 3mm is a lot more inward toe.

When you say "add two flats" what does that mean? I gather I'll be loosening the jam nut on rear tie rods where they meet the outer tie rod ends, then spinning the rod itself toward the front of the car, but that's all I can gather.

 

There are six flats on the toe link, like a hex nut, that you use to turn the rod itself. Move it two flats. It is very easy to get disoriented laying backwards on the car, so double check that you’re pushing the rear of the tire out/front of the tire in. Also, you’re looking for actual movement of the threaded rod into the rod end. Since the rod end will rotate around the ball joint, pay attention to what movement you’re seeing.

IIRC, each flat is about 1/32”, so you’re adding about 1/16” per side. Drive it and see the results. If you like it, you have an idea of what it needs when you go back to the alignment shop at the end of the month.

 

Great, thank you. I'm learning this new terminology. The green arrow is pointing to a flat, correct?




So if there are 6 of them like a nut has 6 sides, then I just need to rotate the tie rod 1/6th of a turn so the flats move to the next position. And then one more time to say I moved it two flats?

 

Exactly.

 

2nd on the idea of adding 2 flats of toe in at the rear.
Make sure to mark your starting position! It's way too easy to lose reference otherwise.

 

.09" in will be a lot yes but a good test and easy enough to switch in less if you find it goes well. (.03 plus your new add .06)

 

I am back with updates. I took it back to the shop and asked them to turn it two flats to see how the toe changed. In a nice way, they basically laughed at the term "flats" as a means of adjustment but humored me.

When they got it back on the rack, the alignment specs were slightly different than when it came off the rack for the first alignment, but told me it was within a normal tolerance.

When they adjusted one "flat", it changed the toe .06. So for example, the left rear was .03in and one turn of the flat moved it to .09in.

Also, according to the front desk guy, turning the right rear tie rod toward the front of the car adds toe in while turning the left rear tie rod toward the rear is what adds toe in.

Here is how the original alignment turned out:



How it measured when I pulled onto the rack today:



And how I left today:



With just that small amount of toe in added, it made all the difference. The rear end really wanted to walk out in tight turns but now it's much better. They said .10 total toe was the max within OEM spec and even then the .05 on the left rear was teetering on out of spec (as it is red). I wish the camber was a little more even but all in all I am happy. The main thing is that it feels planted again.

Thanks for the advice, hopefully someone else can find this thread and solve their issue if they experience the same as me.

 

That looks great! Is your car lowered at all?

 

Slightly compared to the OEM ride height chart but still on the stock bolts. Came with lowering bolts when I bought it and hated them so I switched them out.

Front is even at 26.5" from ground to fender, rear is even at 27.5" with 3/4 tank of gas. The rear end does squat a bit with a full tank vs empty.

 

Just my opinion, but 35 psi cold is too much. The door placard says 30 psi, and I have found that to be a really good number. I will let it get down to 28 before I add air.

 

suggest using the 30psi cold as per the placard. it works well for street/normal usage and tires wear nicely. Mine only gain 2~4psi when warm (again, 'street/highway')