245/35/20 F w/ 275/30/20 R is an OEM sizing for xDrives

Unspec · 05-25-2021, 10:36 AM

Was browsing the owner's manual for tire sizes and noticed that 245/35/20 and 275/30/20 are a listed OEM sizing for xDrives. If you calculate it, it's actually a -1.1% difference, with the fronts being taller than the rears, which breaks the conventional wisdom of "xDrive = <1% difference". Any theories? My personal one is that the front of the car is heavier, which squishes the fronts more and brings it within the 1% tolerance range.

remmib · 05-25-2021, 06:09 PM

Quote:

Originally Posted by Unspec

Was browsing the owner's manual for tire sizes and noticed that 245/35/20 and 275/30/20 are a listed OEM sizing for xDrives. If you calculate it, it's actually a -1.1% difference, with the fronts being taller than the rears, which breaks the conventional wisdom of "xDrive = <1% difference". Any theories? My personal one is that the front of the car is heavier, which squishes the fronts more and brings it within the 1% tolerance range.

OEM wheels are star marked and the front and rear are matched so the diameter is the same.

Hoa · 05-25-2021, 07:52 PM

I've used this setup for about 40K miles before without any issues. I do hear a little more "gear" noise compared to non staggered . I switched to M5 wheels with 255 and 295 later and the noise is less so it does matter a little but won't destroy your drivetrain

Unspec · 05-26-2021, 10:07 AM

Quote:

Originally Posted by remmib

OEM wheels are star marked and the front and rear are matched so the diameter is the same.

But wouldn't the math just not work out for 245/35 and 275/30? Unless they fudge the sidewall height slightly to match them?

05-25-2021, 10:36 AM	#1
Unspec Colonel 1295 Rep 2,587 Posts Drives: 2015 BMW 535xi Join Date: Apr 2019 Location: DMV iTrader: (1)	245/35/20 F w/ 275/30/20 R is an OEM sizing for xDrives Was browsing the owner's manual for tire sizes and noticed that 245/35/20 and 275/30/20 are a listed OEM sizing for xDrives. If you calculate it, it's actually a -1.1% difference, with the fronts being taller than the rears, which breaks the conventional wisdom of "xDrive = <1% difference". Any theories? My personal one is that the front of the car is heavier, which squishes the fronts more and brings it within the 1% tolerance range. Attached Images __________________ 2015 BMW 535xi Bootmod3 Stage 2 \| ER charge pipe \| ER Catted DP \| Remus Exhaust \| Gplus FMIC \| KW V3 \| Turner Monoball thrust arm bushings \| Wallet regrets ISTA VM Setup/Tutorial
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05-25-2021, 07:52 PM	#3
Hoa Major 513 Rep 1,356 Posts Drives: BMW Join Date: May 2010 Location: GA iTrader: (9)	I've used this setup for about 40K miles before without any issues. I do hear a little more "gear" noise compared to non staggered . I switched to M5 wheels with 255 and 295 later and the noise is less so it does matter a little but won't destroy your drivetrain
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