MobyDickDog

Are the Performance Street alignment specs within GM's alignment spec numbers?

JoesC5

yes except for the rear camber. The low side of the Pfadt is slightly under factory specs.

R50THC5

Just had mine adjusted to rid myself of the slow turn thump thump. Had a copy of the Pfadt specfics (multiple settings) and went for best tire wear. Tech said they are pretty close to GM's specs..The front right was way out and so was the right rear when put on the machine. Why it left Bowling Green this bad is odd. Unfortunately, due to the large tire size, the thump thump sliding still occurs (1100 miles). Almost worse than before. Will have it checked again next summer or if tire start to show a bad wear pattern. We shall see.

terradriller

I had my 427 60th annivesary aligned when it had about 1,100 miles on it. I had it done to the PFADT street spec's so I can get the maximum life out of the tires and to improve the overall handling of the car. The car was extremely twitchy on the road, every crack or tar strip it hit would jerk the car from one side to the other.

The PFADT alignment helped alot, took out about 80 to 90% of the twitchyness, but it still has some in it. Wondering if you had the same issue with your car.....

I do love the 427 vert...

427

raysk

I don't think the thump thump goes away with an alignment? I received a notice at my dealer that it's normal. stated fix is to turn the care 1/4 turn less of the steering wheel.

Knob Jockey

IMHO there is too much allowance for variation in the GM specs.

The key is to have the alignment done to tight tolerances, not just in the ballpark.

I had mine done to the PFADT street/track specs and the car tracks a bit looser now.

I also had the car corner balanced.

A good shop/tech can make all the difference.

08redvette

yes my 08 Z51 does same thing right front worn out after 10600 rest look good

terradriller

What is corner balanced??

FiremanC7

Corner balancing is usually done to cars equipped with coilover adjustable suspension. It involves placing each tire on a weight scale and then adjusting each coilover to equalize the weight at each wheel.
Enhances handling and balance of the vehicle.

terradriller

Thanks .. So any thoughts on the twitchy handling of my car??

427

v1 rot8

interested

SG4206

Can be accomplished with factory springs. Wonder why each corner has an adjustment bolt. This is not just for ride height.
My car from the factory was 110 lbs. heavy on the left front with out me in the car .

Gearhead Jim

The Pfadt specs allow, but do not require, a slight amount of toe-IN both front and rear. Their numbers show it as a " - " (minus), but every alignment machine around here uses " - " as toe-OUT.

You could talk to your alignment guy and verify that you have some slight toe-IN on both ends. When we went from 0 toe to slight toe-in, the car became more stable on the highway and over bumps. Steering response will be slightly less in theory, but i couldn't see any degradation there.

Bill Dearborn

There doesn't seem to be any real standard on whether toe in is positive or negative. GM specs use positive while the Pfadt specs use negative. Same goes for alignment machines. Have seen it done both ways. Best thing to do is to write down any specs you want and use the words "Toe In" or "Toe Out" instead of trusting that using positive or negative symbols will get what you want.

The GM alignment specs are shown in the top PDF file and the Pfadt specs are shown in the bottom PDF file. FE1 and FE2 are for base, FE3 is for Z51, FE4 is for Z06 and FE5 is for ZR1. My manuals only go to 2009 so I don't have the GS specs but they are probably similar to the FE3/Z51 specs. Check your RPO sticker in the glove box to see which FE code is listed if you have a GS.

Bill

terradriller

When I get time I'll post the actual alignment numbers before and after...

Thanks


427

terradriller

Hi Bill, here are my before and after numbers on my 2013, 427 annivesary vert ....


Front: Left Front: Right

After Before Range After Before Range
-0.8* -0.7* -0.9 -.07 Camber -0.8* -1.0* -0.9 -0.7*
7.7* 7.1* 7.5 8.5* Caster 7.8* 7.1* 7.5 8.5*
-0.06* -0.19 -0.08* 0.00* Toe -0.05* -0.35* -0.08* 0.00

Rear: Left Rear: Right

After Before Range After Before Range
-0.4* -0.40* -0.6* -0.4* Camber -0.4* -1.0* -0.6 -0.4*
-0.03* +0.59* -0.08* 0.00* Toe -0.02* -0.08* -0.08* 0.00*

As I said before the alignment took out a lot of the tightness (twitchy) feel of the car, but it still wants to track over some cracks and tar strips in the road....

Thanks for the look and your thoughts


427