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  #31  
Old 01-09-2014, 09:48 PM
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Quote:
Originally Posted by ard View Post
truck..truck...truck???

Hmmm...

Oh, you mean the X5?!?!?? Its not a truck.
I hear you...but I thought BMW chose to have the feds classify the X5 as a truck. Or perhaps we mistakenly call it a truck given that it replaced a 15 year old Explorer that we always called "the truck" :-)
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  #32  
Old 01-09-2014, 09:56 PM
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Quote:
Originally Posted by conedoctor View Post
This is all assuming you have the correct width wheels, some of the aftermarket stuff is narrower than OEM.
I do have a different set of wheels for the winter tires, different design, but genuine BMW (but wrong model year) and the correct size and offset. And I was seeing the same wear on the summer tires, and they are mounted on the original wheels installed at the factory.
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  #33  
Old 01-10-2014, 12:26 PM
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Lets see a picture of the wear and I will be able to give you an idea why it is wearing.
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  #34  
Old 01-10-2014, 02:02 PM
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Originally Posted by conedoctor View Post
Lets see a picture of the wear and I will be able to give you an idea why it is wearing.
This the right front (winter) tire. Has about 14k miles on it, and it's in its 3rd season.

A bit difficult to see, but the worst wear is on the outside, and there is some wear on the inside too, but to a lesser extent. The left front tire is wearing similarly. But it looks to me like they will still be good for at least one more season after the current one. And the summer front tires have worn in a similar manner, but even more so, but they look like they should be good for at least one more season too.

I assume the fact that the inside and outside are BOTH showing wear would tend to indicate underinflation, but I check the pressures at least monthly. And I assume the fact that the outside is wearing the most on both the left and right tires would tend to be interpreted as cornering too hard (of course it could be alignment, but my gut tells me not).

Like I said, I think I noticed that when I took the pressure up to 42 from the door jamb spec of 33, the uneven wear (on the fronts) stopped.

I noticed that all 4 rear tires (winter and summer) have worn slightly more on the inside edge versus the outside edge, and if I recall correctly, that's what other owners with 20 inch wheels have reported. But when I added the 9 pounds to the winter rears to match the 9 pounds added to summer rears (to match the 100 mph sticker on the door jamb, it looks like I quickly wore the centers nearly down to the wear bars. So those two tires will clearly be toast at the end of this winter season. The summer rears (with about 16k miles on them now) look like they will be ok for one more season.
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  #35  
Old 01-10-2014, 02:51 PM
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First the picture does not help a ton but here we go.

Are there little rubber flaps on the back edge of all the outside tread blocks?

That would be a tow out issue, raising the pressure way up may have stopped it because it out pull the outside edge of the tire up a bit as the center of the tire gets rounder, sort of solving your wear issue but not fixing the problem. If you are turning too hard you will get the corner of the tread getting round and not square and this will not happen on the inside, if you are wearing the two outside edges on the shoulder of the tread the tire is flat not under inflated so I don't think that is your problem.

You could also have a failed bushing that shifts the alignment under load but not both sides.


The rears are wearing due to camber, buy adding air I think you pushed the center out reducing the contact patch so stopped wear but not a good way to do it. Every BMW I see has tons of negative rear camber, with such a wide tire I think they could get away with less camber in the back.
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  #36  
Old 01-10-2014, 06:39 PM
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Quote:
Originally Posted by conedoctor View Post
The rears are wearing due to camber, buy adding air I think you pushed the center out reducing the contact patch so stopped wear but not a good way to do it. Every BMW I see has tons of negative rear camber, with such a wide tire I think they could get away with less camber in the back.
No, I think the rears wore more quickly due to overinflation. It was worse (more rapid wear) with overinflation. Classic centre-tread wear.

The rear camber is very unfairly blamed for most rear tire wear. In fact rapid rear tire wear on the edges is largely due to excess rear toe, not the camber. The camber compounds it, which is why if you have a toe problem the inner wears more than the outer, but it starts with toe. Fix the toe and the camber is largely irrelevant. And improves handling, as designed.
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  #37  
Old 01-10-2014, 06:48 PM
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Thanks again. From what you described, it seems like a combination of cornering too fast and underinflation. But I really don't push the truck that hard in the curves and corners often at all, and I'm very good about checking the pressures.

Since running the fronts at 42 but keeping the rears at 36 does not seem to have upset the handling balance (I was out on snow covered roads as well as wet roads today here) I'm going to go with that for a while and see how the tires wear. Will let you know the results.
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  #38  
Old 01-10-2014, 09:09 PM
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I will agree to disagree on the rear wear, years of driving an AutoX car back and forth to events has eaten a fair share of inside tire edges, I do agree toe will make it worse. Now if the wear is nice and just worn then I would say camber but if you see cupping or feathering then toe, but toe wont usually wear the shoulder or edge of the tread more the face.

The over inflation hands down caused the center tread wear, but a higher pressure stopped the inside edge wear and if toe was the issue it would start wearing a strip out of the tire tread. I may have an old tire I can show it on.

I use lots of toe and camber and have seen all sorts of odd wear patterns.

I don't think the front is underinflated, if they were so low you were wearing the edges the TPMS would have told you, that said the 275/40 on a 10" wheel could use the higher end of the pressure range to help the center fill out. I think you have a toe issue, like too much in if you are getting feathered outer edges.
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  #39  
Old 01-10-2014, 11:47 PM
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Originally Posted by conedoctor View Post
....toe wont usually wear the shoulder or edge of the tread more the face.
It has been shown to do so on the rear of the X5, when equipped with oversized rear tires, ie 20". Adjusting toe to the minimum of the published (wide) range has greatly extended tire life with respect to premature inner edge wear.
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