I have an '04 MCS, with about 86,000 miles on it. I have Bridgestone G019 tires mounted all around. These tires have a 50,000 mile warranty if I get them rotated annually.

Last year, there were no problems and the tires were wearing evenly. This year, both rear tires showed even wear across the face of the tire (that is, no cupping, no feathering), but there were regular dips and valleys on the tire. I could almost describe it as the circle was developing into an octagon. It only happened on the rears, not on the fronts, and it was on the rears symmetrically. It's noticeable if you run your hand around the circumference of the tire, but not noticeable enough to cause noise or vibration. The depth of wear is not different from the fronts (the tires have been rotated regularly).

Firestone pointed this out to me, and agreed to honor the warranty on the remaining life of the tire. However, if it is a suspension problem, I need to look into that.

The suspension seems fine, and the Firestone people didn't see anything obvious. Struts seem fine, but they are original and maybe getting a little old, but there is no obvious visible problem. The alignment is spot on.

Has anyone had this problem? I did a search, but nothing like this appeared.

Is it possible that I have two defective tires conveniently on the same axle? What gives?

 

Do you do a lot of intense turning that results in understeer? When you understeer, your back tires are essentially dragging sideways on the ground behind you, and that can lead to wear patterns like that. It happened on my friend's GSR.

 

You mean oversteer. But that does not necessarily cause cupping as described. Could be you need a toe adjustments or bad shocks.

Understeer causes the front tires to wear prematurely.

 

It could be bad shocks, I suppose, since I don't generally perform skidding turns. I just have a hard time picturing how the wear I described could occur. The rear end doesn't oscillate, and all the suspension elements seem tight.

A puzzle.

 

My first guess is failed rear shocks. The only way to check them is to pull them off and remove the spring.

 

The tires could be out of balance a bit, it's a cheap thing to check out.

Dave

 

Dave - I had them balanced on the same visit. They were not perfect, but close.

onasled - Shocks seem to be the only answer, but how does the shock action cause this kind of wear. I'm not a mechanical newbie, but this is new to me.

 

The shocks are not controlling the springs, so your tires start to bounce. Any tire irregularity will be enhanced as as it's now free to bounce over and over again, unnoticeable at first, until this pattern that you describe is shaped. Tire rotates, bounces due to irregularity, and the tire patch just behind that irregularity now has less force on it as the tire is becoming unweighted thus wearing away slower. Tire then rebounds with added force to the pavement and that patch is now worn away faster. Over and over again, until the tire becomes the shape you are finding on your rear tires.

 

I see. So I need to replace the shocks before I take Bridgestone's generous offer to honor the warranty.

Separately, I put on these G019's to replace the original runflats, and (other than the wear discussed in this thread) they have been terrific daily drivers, and good in the snow.

Thanks to all.

 

My front and rear Michelin Pilot Sport A/S have done the same thing. When I remove them, they will not even roll down the driveway without wobbling back and forth!

Notice the darker sections of the inside...

 

Based on your description and the picture SidSwift posted, it sounds like the tires starting to cup.

This happened to me before, and eventually I started to hear it. I let it go for awhile and the noise became too loud to bear, so I went to the local tire shop and they said it's probably happening because the alignment is off. They did a four wheel alignment and I put on a brand new set of tires and I figured I was good.. until a couple months later the noise started coming back. I took my car to the MINI dealer and they said the alignment was way off (way to go Tire Express), did it to MINI standards, and haven't had a problem since (2 years). FYI, it only happened on my rear tires as well. Unfortunately since I rotated frequently I ruined all 4 tires...

I would get an alignment as a precautionary measure before they start cupping bad enough to make noise.

 

My alignment is pretty new, and I was hovering around so much when they did it, that they invoked the "authorized persons only" clause. But I did see the right specs on the machine.

But I appreciate all the suggestions and will let you all know what I finally find out.

Thanks.