I removed my from wheels today to clean them and noticed the inside edge of both front tires were "scalloped" (I think that is the correct term). The outside edge looked perfectly round and the inside edge looked like a 50 sided polygon with each side about 2" long. Before I take my car to the alignment shop, what type of alignment problem is this? Is this a common condition with Vettes and could running the tires with ~26 lbs of air pressure for a couple of months cause this condition?

Thanks in advance for the help.

 

pdm, thats normal wear characteristics for the C5. The 26# of pressure didn's cause the problem, but it probably contributed to the wear. The wear you describe is really from normal street driving on the neg. camber settings GM has on the car for better cornering performance. You can align for more even tire wear if you are not so concerned about having max. cornering ability.

 

Hey Alan,
What settings are recommended for the most even tire wear. I am not so concerned about maximum cornering ability, just even tire wear! I have the OEM specs and my alignment guy will set it to whatever I want.

Mike

 

Mike, here's one of my old posts on the subject and the settings I'm still running.

Here's my thoughts on alignment. I too had tire wear problems and was running on my third set of front tires by the time I acquired enough information about the C5 alignment to get things figured out, (I think). I set my own alignment in my home shop so I can try lots of settings with little expense.
First off, keep this in mind, you're driving a high performance car and a little aggressive tire wear is not out of line for a performance car.
According to GM document #776629 which gives alignment specs for the C5 & Z06, the (Preferred Front Camber is -.20 degree) for the FE1 & FE3 suspension. The (Camber Tolerance is +/- .50 degree). So if your front camber is anywhere between (-.70 degree to +.30 degree), you are within GM specs. You hardly need an alignment machine to get camber within that tolerance, that's almost in eyeball range.
The Good Year run flat tires have a wide square shoulder tread and very hard sidewall which will put much more pressure on the edges of the tread, due to a small camber angle, and will result in what seems to be aggressive tread wear on the edges of the tread, usually the inside. Non-runflat tires have a much softer more compliant sidewall and is part of the reason the Z06 camber is more negative.
The more square (0 degree camber) you set the runflat tire with the road, the less abnormal tread wear you will see.
I think it would be a wise move for GM to provide a set of "performance specifications" for aggressive driving, and another set of "touring specifications" for normal highway driving. They would need to provide a brief pro & con statement of the two specs and let the driver decide which way he wants his car set up.
So, back to the question as to what to use for good tire wear. Following is what I am currently running and with 8000 miles on the Stone RFT’s , there is no measurable or visible wear variation in the tread.

Front
Camber: 0.0 degree, (error to the pos. side less than .10 degree if not exactly 0)
Caster: 5.0 degree, (steers a little easier and not nearly as important for street as it is for performance)
Total Toe: 0.1 degree pos.
Rear
Camber: 0.0 degree, (error to the neg. side less than .10 degree if not exactly 0)
Total Toe: 0.0 degree to neg. 0.1 degree

 

I am a very agressive driver and I have no wear on the front inside of the EMT's. I thing that the C5 alignment is very straight and you should not have negative camber wear on the stock alignment.

You can get a road course or Z06 alignment and it might affect your tire wear but for a stock C5 your should not be getting negative camber wear.

I used to have 928's before I got the C5 and it was next to impossible to prevent negative camber wear. 15-29k miles were tops for tire wear.

My C5 street tires wear very evenly.

As a side note my dealer just told me they bought a very high-tech alignment machine that measures with cameras and mirrors (he probably ment camera's and lasers, he is most likely use't to the smoke and mirrors technique)

 

I just got my 99 Coupe aligned this past Friday. At 10,000, I was seeing some cupping on the inner edges of the tires. I was told that, front tire cupping is commom on the C5's. :chevy


[Modified by Tom/99, 7:16 AM 10/22/2001]