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      01-26-2021, 09:38 AM   #1
Moedee
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275/45/r21vs 275/40/r21 --question . . .

The standard for the 21 rims will be 275/40/R21 in the front

if i wanted more sidewall bumping it to 275/45/R21 - how much of a difference is that really going to make?
has anyone seen less problems going up by 5 ?
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      01-26-2021, 10:06 AM   #2
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you'll have slight speedometer discrepancies (reading about 1-3 miles faster as you increase speed). Maximus2002 is happy running that tire size.
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      01-26-2021, 10:44 PM   #3
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You'll also need to change the rear to an equivalent rolling diameter.

OEM front 275/40R21 = rear 315/35R21 = 29.7" rolling diameter.

275/45R21 = 30.7" with 656 revs per mile which is 3.3% larger in diameter compared to the OEM 315/35R21 rear which will F'up xDrive.

You'll want the front and rear diameters to be within 1%, necessitating rear sizing 315/40R21 which is 652 revs per mile or 0.6% / 0.3mph less than your planned 275/45R21 size change.
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      01-27-2021, 08:20 AM   #4
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I was wondering that, & you answered my question
much appreciated !!
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