firebirdStud

Hi all.

I have a daily driver bird, 95, full weight. I have Goodyear Eagle GSD2 rubber, 275/30zr18's up front and 295/35zr18's out back. They are on Vette chromed out Z06 wheels.

I put the rubber on about 7xxx miles ago, and did an alignment myself at the time. (I work at a Chevy dealership) I did the alignment to stock specs.

I have had the tires set at 32 to 34 psi since they were put on. (I say that because I looked at my log, and the first summer was 32, the second summer was 34... not sure why I changed, but I did.)

I checked tread depth, and the rears are at 9/32nds all the way acrossed the face. The fronts are at 9/32nds in the middle, and the outsides are at 5/32nds and the insides are at 6/32nds.

Anyways, looking at the car now, the outsides of the front tires are worn down more than the middle or the inside. The car tracks fine, but Im wondering if I need to adjust the alignment to specs other then stock. I have a built motor in it, with a Dana 60 and a viper conversion t-56... I drive it hard. I like to take corners fast as well... Is this why the front tires are wearing so quickly on the outsides??

What tire pressures work well to help combat this, and should I re-align it to some other spec??

I am trying to get a feel for what other people have experienced and have learned what works well for these cars.

I do want to stress, this is a daily driver. I will be taking it on a 9 hr road trip this thursday for a family wedding, so I dont want really agressive alignments where the inside of the tires will wear from agressive camber... trying to find a happy medium I guess..

Many thanks!!!
Cody

dangalla

you could have posted 3 words and a picture and explained this so much better

that would usually indicate to me low tire pressure, what does your manual list as the spec though?

firebirdStud

Here is the outside measurement


Here is the middle measurement


Here is the inside measurement

firebirdStud

The owners manual lists tire pressure for the stock size tires... these are far from stock. That was my dilema...

dangalla

personally i would be running a minimum of 35 on the street, out of curiosity have you checked the pressure with a different gauge

that is a pretty drastic wear issue and 9/10 times that would be caused by underinflation

firebirdStud

35 minimum, huh? I will try pumping them up then. I also swung by a goodyear dealer here and they said to use a tire crayon and draw a line across the entire face, drive it for a bit, and look to see how it is wearing to see if the pressure should be adjusted...

I never thought to use a different gauge, that is a good idea too!

bluz28

Yeah, it sounds like you need a little more tire pressure up front!

Injuneer

Edge wear, on both edges of the front is normal, particularly if you corner hard (although it may be worsened by under-inflation). At 7,000 miles you would typically rotate the tires, but therein lies the problems of a staggered fitment - no way to "rotate".

firebirdStud

I just got back from the road trip to the Black Hills. I was too busy before I left, but here are the readings from the alignment:
BEFORE:
Caster
left 4.9
right 5.0
Camber
left .3
right .2
Toe
left .25
right .2
total .45

AFTER
Caster
left 4.3
right 4.4
Camber
left -.2
right -.2
Toe
right 0
left 0
total 0

Im a little perplexed by how far off the alignment was. I guess two years of daily driving will throw things out of whack?
I checked the ball joints and tie rod ends and everything was snug before I did the alignment.

Driving out to the Black Hills and back (1500+ miles total) was like a dream. The car tracked straight, rolled into corners nicely and held the path firmly. Im very glad I checked the alignment and corrected it. I also pumped up the tires to 35psi.

I haven't had a chance to re-evaluate the tires yet, hopefully tomorrow.

So that is the update so far!

firebirdStud

I know, not being able to rotate the tires will kill the front ones... ugh. But I just cant see rollin 295's up front.

I guess Im just trying to minimize the wearing of the front as much as possible...

Injuneer

Did the tires start with a uniform tread depth across the full face of the tread? I know the factory Goodyear GS-C's had less tread depth on the "outer" side of the tread than the rest of the tire. It always caused problems with people thinking there was premature wear. But the tires were made that way.

firebirdStud

you know, Im not sure. I guess I never checked before I put them on, and never cared until I found this problem.. Hindsight is always 20/20. damn. I guess this might be something to look into. How would I go about figuring that out?

firebirdStud

I think you are on to something!

I did a quick measurement of all four tires, and this is what I found:
------------------outside--middle---inside
Front Drivers------5--------9--------5
Front Passengers--5--------9--------5
Rear Drivers-------6--------8--------6
Rear Passengers---6--------8--------6

Looks like maybe the tires came as you described... less tread on the outsides of the tires.

I also measured some high speed tires at work, brand new, and the outsides were 3/32nds less tread then the middles. This makes sense, and now that the alignment is correct, I will just keep an eye on them to see how they wear from here on out.

Again, thank you everyone for your input!
Cody

firebirdStud

WTF, the spacing didn't hold up. I made a little table for the tread depths, and that didn't stay put.

Injuneer

You can't set up a table using spaces. The system only recognizes the first one in a series. You have to use periods or dashes.