What's going on with my tire wear- rears are wearing out in the middle?

[JavX5]

I have staggered 20's and I'm about to buy a new set of Toyo Proxes STII's for my 4.8is. Before I flip the bill, I want to make sure my new tires won't wear like my old ones.

I've read many threads about uneven tire wear, and camber settings, but most of them talk about the tires wearing out on the sides, not the middle. I bought the car a year ago and the old tires had the same type of wear in the rears. I bought some used rear ones to get me through this year, but they have worn out the same way. I had it realigned to specs by a good BMW shop before I put on the most recent replacements.

Any suggestions on what I need to do to make sure the new ones wear out evenly?

[franikk]

What psi are you running? That would be my first thought.

[duboy]

possibly overinflation? what PSI are you running back there?

[X5one]

I run my rears at 36psi and they wear somewhat even.

[JavX5]

I've always let the BMW shop figure out my PSI, but I'll check it now...

[Jordo]

It looks like text book over-inflation. That's my bet.

[Naz24]

definitely overinflation

[JavX5]

I'm at 35 PSI in the back, any suggestions...

[Jordo]

Ok, this is an old motorcycle trick.......

If you can SLOWLY drive/push your X through VERY SMALL/THIN sheet of water, when you come out of it, onto the dry concrete (concrete works better then asphalt) you will be able to see the contact patch of your tires.

My guess is the two outside areas of the tire will not make contact with the water or transfer the print to the dry area. Still tho, if this is the case I would not suggest lowering the tire pressure.

[JavX5]

Interesting experiment, but I don't see what I can do with it, look below...