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      11-28-2021, 08:14 AM   #1
Justin850
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I wanted to go with 22" wheels all around for my 2021 X5M Competition. So I purchased the new wheels, used the existing rear tires and got a new set of 295/35/22 for up front. The new tire size is about 3% larger than stock and it seems to give the computer for the transmission fits in manual driving; doesn't at all in assisted driving mode. I was told that as long as the new front set was within 5% of stock there shouldn't be an issue. Has anyone else run into this and is there a way to adjust the computer for the size difference?
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      11-28-2021, 02:53 PM   #2
nZtiZia
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Originally Posted by Justin850 View Post
I wanted to go with 22" wheels all around for my 2021 X5M Competition. So I purchased the new wheels, used the existing rear tires and got a new set of 295/35/22 for up front. The new tire size is about 3% larger than stock and it seems to give the computer for the transmission fits in manual driving; doesn't at all in assisted driving mode. I was told that as long as the new front set was within 5% of stock there shouldn't be an issue. Has anyone else run into this and is there a way to adjust the computer for the size difference?
5% is way too high. most manufacturers advise being within 1-3% of original tire specs for AWD, but I'd err closer to 1%, especially on a vehicle of this caliber.

I believe the OEM wheel/tire setup for your MY21 X5MC is 295/35R21 front and 315/30R22 rear, correct? that would make the OEM rear tire circumference 1% larger than the OEM front (1st photo) which is within BMW xDrive tolerance. with 295/35R22, your new front tire circumference is 3.4% larger than the OEM front tire (2nd photo), and since you kept your OEM rear tires, their circumference is now 2.3% smaller than the new front tires (3rd photo). with your new setup, your OEM rear rolling circumference went from 1% larger to 2.3% smaller than the front, so the delta is 3.3%. safe to assume your vehicle isn't new, so your rear tires already have some tread wear while front tires are new which may also account for the rear circumference to be even smaller, making the delta slightly larger.

looking at the 3rd photo, it's obvious how much larger your new front tires are compared to your OEM rear tires and is why your xDrive drivetrain doesn't like it. BOTTOM LINE: the front 295/35R22 you mounted are the wrong size. below are the two front tire sizes that would make the rears ~1% larger than the fronts and bring you close to OEM spec again. the challenge will be finding matching front and rear tire brand/model.
295/30R22 (4th photo)
305/30R22 (5th photo)
**you may have better matching luck with 275/35R22 in the fronts which'll make the OEM rears 0.7% smaller than the front. the delta is 1.7% from OEM-spec.

modifying or adjusting the computer to 'accept' the new tire differences won't take away the underlying mechanical stress you're putting on the drivetrain with your current tire setup. adjusting the computer is merely applying a bandaid on the problem. **best to get new front tires (can still keep the 22" wheels) which is a lot less expensive than a drivetrain repair that will likely not be covered under warranty!
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Last edited by nZtiZia; 11-29-2021 at 01:33 PM..
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