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[Lotus99]

I've got a 535 XI wagon with 245/40/18 Goodyear NCT5 RFT's all around. I've got an RFT in the front that has a bubble on the sidewall, and is at 6/32. A new tire has 10/32 tread. So if I get it replaced under warranty, I'll have one on the front that's 6/32 and another that's 10/32.

Does BMW publish how much difference on the same axle is ok?

1 - Is 4/32 difference ok?
2 - If it is ok, I'm thinking of putting it on the rear and bringing the rear up, so I'll have one 9/32 and one 6/32 on the front, and a 10/32 and 9/32 in the back. Does it matter which side in the front gets the 9/32? (i.e. is it better on driver's or passenger)
3 - If 4/32 is too much, should I get it shaved, and to what tread depth? It seems like a waste to shave it to 6/32? The rears are only at 9/32 (all four of my tires are the same - non staggered)
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I found this article on Tire Rack:

And some mfr specific info:

Audi As published in their vehicle owner's manual, "rolling radius of all 4 tires must remain the same" or within 4/32-inch of each other in remaining tread depth.

Porsche Cayenne within 30% of the other tire on the same axle's remaining treadwear.

Subaru Within 1/4-inch of tire circumference or about 2/32-inch of each other in remaining tread depth.

Replacing Pairs of Tires or Individual Tires

There are several suggestions that have been offered to drivers who are replacing pairs or individual tires on their four-wheel drive and all-wheel drive vehicles. Some vehicle manufacturers recommend that all tires maintain the same rolling radius and circumference, while others suggest that all tire circumferences remain within 1/4- to 1/2-inch of each other.

Other vehicle manufacturers recommend that all four tires remain within 2/32-, 3/32- or 4/32-inch of each other, or within 30% of each other in relative remaining tread depth.

http://www.tirerack.com/tires/tirete....jsp?techid=18
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[Lotus99]

PS While I'm at it, just curious, what would you do? Get a new tire for half price or so (there's a prorated warranty on these), in which case I'd have two at 9/32, one at 10/32, and one at 6/32?

Or get a used one (let's assume) around 6/32 where I'd end up with two at 9/32 and two at 6/32. Then my fronts would run out and I'd have two on the rear still at 5/32 (assume even wear).

Maybe I'm better off getting a new one now, and then when the one remaining "old" front wears down, hope I can find a used one that matches the other 3 that might be around 5/32 then, so I can get full use out of them?

This sucks.