docsout

On 20" Goodyear runflats at 27K miles, I had a pressure failure in the right rear. At dealer, tread looked good, no foreign object, outside looked good. But, on the inside, i.e., facing the differential there was tread failure with wires showing. I asked what's the deal here. Response was rear wheels are at a camber, (forgive me but, I don't know the technical term) tilting outward away from the center of the car. And, there is no adjustment for this in the rear wheels. My question is, why is there an outward cant? Why not have the rear tires roll flat or true?

insame1

http://bfy.tw/8lwJ

Mitch Alsup

A tire with a small amount of camber produces a stabilizing force as the car drives down the road. This helps make the car drive straight with your hands off the wheel on crowned roads.

The mystifying thing is the shredding of the tire wall on the inside edge. In any event it is easy to put the car on the lift and investigate what in the rear suspension could be close enough to make contact with the tire.

Shadow5501

Actually, what you have is negative camber - the top of the tire tilts in towards the center of the car. This is normal and quite intentional. Link to a wiki article on camber if you are really interested: https://en.wikipedia.org/wiki/Camber_angle. Typical road cars have perhaps -1.5 degrees of camber.


The tire didn't fail, it just wore out and you did not notice. Things that contribute to it are wider than stock wheels/tires, driving cars with adjustable suspension in the low setting, hard acceleration, coarse road surfaces, and of course bad luck. The E55 AMG guys have this same problem, for these same reasons.


What can be done about it? Have the alignment checked to insure it is within specification. If out of specification, repair it. If within, keep closer tabs on inside rear tire wear...

hyperion667

27K seems pretty good

docsout

Thank you all for the education. It's physics and calculus. Rather interesting. Again, merci.

lsdreem

I agree, 27k from any set of tires on a car this heavy is more than reasonable.

docsout

I appreciate every one's comments.
I was not complaining of getting 27K miles out of the tires.
What I was surprised about was the wear down to the wires on the inside of the tire due to the camber yet, no visible excess wear on the tread or the 'monitoring bars in the tread grooves. I wasn't expecting that. I was thinking foreign body. To me, it was just interesting and for me, unexpected.

swaynesworld

Shadow5501 gave you an excellent post on your "Tire Failure" post. All I would add is that your tires did not fail nor did they wear in a way that gave evidence to a tire defect. Be careful putting that many miles on this car as a blown tire could prove disastrous. I got 17K out of my Pireeli RF's which is really good especially with the hard driving I do.

Nice Ride

Normally I replace my tires before they get too low on the ware indicators (Monitoring Bars). Tires are still good for most, but rain / snow will do better with more rubber... Also, if you don't drive the car much, tires will and do start to dry rot especially if out in the sun. Age is also a factor on tires.

Good luck with your new tires and make sure you get MB alignment. It is not a simple one to do on any rack.