PLEASE HELP! 18'' 20'' 21'' TIRERS! SENSORS...
 

TIRES:

I'd figure I ask the experts here on the forum so I don't mess my SAV up for lack of knowledge. I have a 2008 X5 3.0si that came stock with Style 210 18" wheels and Bridgestone Dueler HL 255/55r18 tires all around. This past summer I came across a good deal on a set of 21" Style 215 wheels with no tires. Searched online and found out that from factory they come with Dunlop Sportmaxx SP "325/30/R21 REAR" and "285/35/R21 FRONT". So I purchased the tires and mounted them and all fitted and drove nicely. But a friend raised a concern when he mentioned that the overall diameter should be same all around due to the car being AWD or I'd be looking at a damaged differential. So is tire size setup I have on the 21"s incorrect? And I recently got a set of 20" Y spoke style 214 wheels to replace the 18"s on the winter. Tire setup again is different rears from the front. 315/35R20 REAR and 275/40R20 FRONT. So is it ok to run these configurations on my X5, or will it cause any damage? Idea is to have the big 21"s during summer and the nice 20"s during winter.


TPM SENSORS:

As far as TPM sensors, another whole dilemma I'm having. The 21"s came with some BMW TPM sensor that the guy I bought the wheels from said they would work fine with my X5. Fact is the tire pressure yellow light and warning popped on the dash and wouldn't reset. My mechanic tried to configure it with his SnapOn tool with no luck. Is this something that only the BMW dealer can program/configure? Soon as I swapped back to the stock 18"s the car recognized and reset the light and was all good. Should I swap out the TPM sensors from my stock 18"s to the 20"s & 21"s when I swap wheels?

Staggered width is fine...Staggered diameter is not, most of the larger BMW wheels come staggered with, even for the X5

The E70 uses two different TPMS sensors depending on production date.

I believe you will get a ABS and DSC warning if the tire diameter is different enough to be detected. Last year with 1 worn rear tire and 1 brand new I was getting DSC activation under hard acceleration.
There are 2 or 3 type of TPMS sensors for X5 E70. I can tell you what to buy to program 4 sensors for your car or i can have a set programmed for you.

tires are fine.
rolling diameter needs to be within 1%. those tire sizes are that.
you need tpms from a 2008- early 2011, the tpms you have must be from a late 2011-2013

This is fine, revs per mile are 723 front and 728 rear, under 1% difference.


You dont list a tire model but a continental DWS these are BOTH 724 revs per mile, so perfectly matched.

You will note I dont discuss diameter- the revs per mile is MUCH MORE PRECISE.