Overinflation

[cpadpl]

I just arrived back from the dealer for inspection service today (14k), had significant and identical center rear tire wear (about 4/32 left in the center) even though I am vigilant about inflating to the doorjam pressure and monitoring thereafter. My suggestion for the rear tire center wear was as follows: I live in Florida and almost anytime I drive, it is on the interstate going at least 70, and perhaps the "standard" recommended tire pressure for the rear is just too high for the 100+ summer temperatures coupled with the heat that is produced from prolonged high speed driving. My service advisor readily dismissed my theory, and is adamant that the wear in the center of the rears is solely due to "the specialized suspension" on my 05 M3, he said he sees it all the time with the M3s and the 3 series in general (guess they have the same specialized suspension?).

Giving my service advisor the benefit of the doubt, my question is - is there something particular about the suspension that could cause the rears to wear in the center? I know that caster has little effect on tire wear (and affects the front only??), camber obviously does, but what could cause identical center wear on the rears? To me, I can't see how it isn't overinflation, it's identical on both tires, and is obviously the result of the side tread not contacting the road while the center tread is. What kind of "specialized suspension" component could cause road contact with the center tread but not side tread, maybe excessive toe?

Anyone else have a similar problem?

 

[Kirby]

I can't explain why it happens, but I have seen it. I did some major upgrades on my E36 recently, and I noticed that the CENTER of both of the rear PZero Neros were worn slightly more than the edges.

 

[gpoints]

I had excessive wear on my passenger side rear a while back. This was because I was intentionally over inflating that side due to a slow leak it had. The thing I've noticed is the M is very sensitive to changes in tire pressure; a few psi +/- and my car would tend to "pull" and wander.

FWIW, I was only over-inflating my tire by maybe 3psi (@43 - 45 psi) and I was seeing tire wear like you're describing.

 

[andreyiv]

If its right in the center of a tire then it is over inflation and nothing else. What the mechanic was referring to was uneven wear due to negative camber in the rear but it wouldn't be in the center of the tire, there would be more wear on the side of the thread that is closer to the center of the car since the tires contact the ground at an angle (instead of _ car _ it is more like \ car / of course no where near that extreme). If you experience over inflation, just deflate the tires a little. There is a way to find the proper pressure you need in your tires (involves chalk and rolling the car on a level surface), the door jamb figures are just guidelines, just a starting point.

Hope this helps.

 

[cpadpl]

Thanks for the responses, I figured it had to be overinflation. It wasn't the mechanic but the service advisor, and he told me that tires should last 1/2 of their normal life on a BMW, not sure if that is true.

The door jamb figures on my M3 are WAY too high, listed as 41 front and 48 rear. The owner's manual, however, says 33 front and 35 rear up to 4 passengers (the 41/48 is fully loaded - don't know why that would be on the door jam). Since it is usually just me in the car, a keep it at the lower number. Even with 35 in the rear, I got under 15k on the tires and clear signs of overinflation, and so I'm going to drop down to 33 or 34 in the rear.

 

[gpoints]

Just as a point of reference, I'm running right at 38psi on all 4 corners (oem 19's).

 

[cpadpl]

Thanks for the info, I've gleaned enough from the info on the Internet about the M3 and the Michelin PS that proper inflation really is something determined by a whole host of factors. With 33 front and 35 rear, I got even front tire wear, but overinflation wear on the rears (not bad, but more overinflation wear than I was comfortable with). Based on my owner's manual, it says 33 front and 35 rear for UP to 4 people. Thus, I believe if 35 is suggested for the rear for all climates and all speeds for up to 4 people, it certainly should be tweaked lower for hot climates at high speeds with 1 person. I plan on running 33/34 until the dog days of summer, then when it gets to 100+, I may go to 33 all around.

The thing I appreciate from you guys here is corroboration that what I saw was indeed overinflation. I tend to err on the side of me being wrong, since it has been a good 15+ years since I even messed with a vehicle (they just got too darn complicated with computers). When I have a service advisor telling me that what I see really isn't the result of overinflation, but special suspension component wear, I feel like I may as well be an uninformed soccer mom....

It's funny how nowadays just common sense and basic knowledge seems to result in being correct over those who purportedly are experts in an area...scary! These forums are invaluable...e.g. I had the infamous right rear spring "boing" on right turns that, had it not been for fellow M3 owners on the Internet, I would still be chasing down to this day.....