A while back my front tires went completely bald on the inside tread. then soon after, the outside tread went bald to. I replaced the stock runflats and had an alignment done...now the new tires are doing the same damn thing..I crawled under the car and cant see any damage or anything bent, but who knows what what is supposed to look like. What should I do here? I'm week's away from new rims and tires...
Any help is appreciated

 

You didn't say where or who did the alignment. It could be worn bushings or some bent parts, bad tie rod ends, etc. The car should have an alignment(4-wheel computer laser) by someone qualified to check all the suspension components.

 

When you had your alignment done, what were the new alignment settings? Then we can help you.

 

Inside and outside wear at the same time is caused by two things
1. under inflation (add a few pounds of air)
2, hard cornering

now since the inside is wearing a bit faster I suspect it needs a bit of toe in also. usually for street use you want a bit of toe in so the wheels point straight ahead when rolling down the road. on the track or auto cross most people use a bit of toe out for quicker turn in.
You'll need a sympathetic and good alignment guy to get it just right for you. Depending on your driving habits and how many miles your tires are lasting your wear mignt be pretty close to correct.

 

I'd be taking a hard look at the CAMBER setting.
Inside edge wear is usually caused by too much negative camber.
Outside edge too much positive camber.

If the rear tires are wearing evenly, take a sighting from the rear of the car and compare the tilt of the front tire/wheel with the rear one.Set the steering straight ahead when you do this and get a few feet behind the car.
Sight down the profile of the rear tire and compare the front to the rear for 'tilt' or 'lean'.

Enough camber to cause wear on the tire edge is easy to see with the 'nekkid' eye.

You can also use a short level to compare the tilt front to rear.

If alignment is correct the tires 'should' be wearing fairly evenly.
Har cornering will normally roll the tire under and cause more outside edge wear.
The uneven suspension arms try to compensate for this by adding negative camber as the chassis loads up but won't stop all of it.

Oh, here's what negative and positive mean:
Negative Camber = Top of tire/wheel leans toward the center of the vehicle.
Positive Camber = Top of wheel/tire leans away from the center of the vehicle.
Zero Camber = Wheel/Tire is straight up, no tilting in or out.

Incorrect toe settings should cause mostly even wear as the entire tire drags across the driving surface.
Incorrect caster evenly distributed shouldn't cause just edge wear.
Cross Caster will cause the car to pull to one side or the other and you will have to constantly apply corrective pressure to the steering wheel.

Eyeball the CAMBER and if you see anything out of the ordinary, go have the suspension checked for bad components then have a FOUR WHEEL ALIGNMENT done on it.

BTW.... LOW TIRE PRESSURE will cause the edges to wear more than the rest of the tire.
HIGH TIRE PRESSURE will cause the center of the tire to wear excessively.

 

FWIW, I have 2 degrees negative camber in front and zero toe and wear tires pretty evenly across tread. There might be 1/32" or less difference from inside to outside of the tire when it is worn out.

Negative camber will wear inside a little more, but if it is coupled with too much toe-in or toe-out, the wear will be dramatic.

You can see 2 degrees negative. It's about 7/8" of an inch at the top of the tire when measured with a carpenter's level and a tape measure!

Beware of someone saying the alignment is within factory specs. You should know the numbers.

Verify your toe in numbers.

 

know where I can get those numbers?

 

thank you for all the info. Last time this happened, They said all the suspension parts were ok. This was at my local dealer

 

Good Stock street settings:

Front
-1.0* camber
Max but equal caster
1/16 to out

Rear

-0.5* camber
1/16 to in


No cross cambers or total numbers

must be EQUAL ON BOTH SIDES, no ranges.

make sure air pressure is equal on both sides.

Once the car is driven on to the rack, bounce it up and down a few times.

 

will this make the tires wear evenly? I swear when i had it aligned a couple months ago it was perfect. now im eating up more front tires

 

No tires ware evenly. you could reduce the camber to -0.5* front and -.25* rear. That should help some.

Rember roads are not perfeclty flat, pot holes, cracks running the direction of the road. bumps curbs and kinds of thing happen.

 

If you continue to use runflats, even 1/4 degree of negative camber will wear the insides of the tires. To get even wear you need to go to 0 degree camber. When my car was new it had 1/4degree negative camber and I got GM to replace two sets of front tires before it became general knowledge that 1/4 degree negative camber would wear the inside edges of runflats if you just do normal street driving. Needless to say, they don't replace tires for this problem anymore. I've been running 0 degree camber for about 6 years now.

 

How are your wheel bearings?? Have you had them checked out??

 

sounds like the rack tech may have used Z06 specs

how's the alignment printout compare to the specs in the shop manual?

what kind of rack? Hunter DSP400 is very common

 

thank you for that info. Im gonna take it to the dealer and have them take it to 0 degrees. Im switching tires in less than a month to non runflats, but id still like to keep these in good shape. they only have 1000 miles on them.