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[DylPickle85]

I'm getting ready to change out my OEM RFT's on my 2008 135i. Currently, I have 19,000 miles on the car.

I had some questions before getting into it. I measured the tread depth on each tire with a pair of calipers, and found the following tread depth for each tire:

Front Right: 6/32" (ranged from 0.175" - 0.19")
Front Left: 6/32" (ranged from 0.18" - 0.21")
Rear Right: 3/32" (ranged from 0.08" - 0.09")
Rear Left: 5/32" (ranged from 0.14" - 0.16")

As you can see, the rears are about due for a change. Also, there's a fair amount of difference in tread depth between adjacent tires, especially the rears. Any comments as to why the tread would wear differently on one side than the other? PSI discrepancy between tires, or something?

I want to at least swap out the rears at this time. This is my first time ever really going through this process on a car of swapping half of the tire set. Is it ok to mix and match like this running the OEM RFT's up front, and new tires in the back of a potentially different brand?

[Tom K.]

If you run your tires down to the wear bars, then your fronts are just about half worn at this point. As it's not a good idea to mix different tire construction types, or even different tread patterns due to possible unstable handling, I'd either replace just the rears with OEM RFTs, or buy 4 new tires.

I had this problem when the OEM tires were not readily available for my 128i, so I went with 4 Conti DWS non run flats for less than the cost of 2 OEM tires.

Tom

[Gary@TireRack]

It is best to keep the tires matched in sets. If that can't happen you should, at the very least, put two similar run flat tires on the back (same performance category.)

[DylPickle85]

thanks for the advice guys. I think I'll wear down the rears to the tread-bar as you mentioned, and then just swap out all 4 tires.

[Nifty]

Originally Posted by DylPickle85

thanks for the advice guys. I think I'll wear down the rears to the tread-bar as you mentioned, and then just swap out all 4 tires.

You're not leasing by any chance are you? If so you will wan't to take the tires off with at least 3/32" of tread left so you can put them back on at lease end.

Actually now that I think about it, I have my stock runflats sitting my garage that have about 800 miles on them. Perhaps there is a deal to be made here...

[aerobod]

Originally Posted by DylPickle85

As you can see, the rears are about due for a change. Also, there's a fair amount of difference in tread depth between adjacent tires, especially the rears. Any comments as to why the tread would wear differently on one side than the other? PSI discrepancy between tires, or something?

All RWD cars that are driven on the right side of the road will tend to wear the right rear tyre more quickly than the left. Various factors cause the right rear tyre to break traction before the left, hence having a higher wear, such as:

1. More sharp turns to the right than the left when driving on the right side of the road.
2. When the car only has a driver as occupant, more weight is placed on the left tyres than right tyres.
3. Coupling differences between the driveshaft and the right and left wheels in an open differential on a BMW - the left wheel is directly coupled to the ring and pinion in the differential, the right wheel is driven indirectly by the spider gears.