[shayzorblade]

Hi folks,

Finalizing a purchase of an F31 with 403m wheels.

I live up north and have an L322 with Nokian WR G4 SUV tires which have served me very well through our winter months. I'd like to fit my new (to me) F31 with Nokia's WR G4 tires as well, and think I have it all figured out.

BMW lists the 403m wheels as 225/40R19 for the front and 255/35R19 for the rear. Nokian makes a matching size for the rear, but they don't make a precise match for the front.

Using a tire size calculator: https://tiresize.com/calculator/

I've calculated that the 225/45R18 is a near perfect match for the 225/40R19 (same width, -0.4% diameter, +14.3% sidewall, -0.4% circumference) and only adds 3 revs per mile (so at 90mph reading it would be 89.7mph actuality).

My concern is this; by having a slightly off front wheel will this cause any issues with the AWD system in my F31? I'd rather not risk it if any issues would arise from this, and am hoping someone here can shed some insight on my decision.

Worst case I go for a full-on winter and swap for summer; but Nokian's all-weather offerings have been fantastic so far and if the above will work without issue then I'm golden.

Thanks for any help anyone can offer!

[chowser51]

You’re going to try and put an 18” tire on a 19” wheel?

I’m confused.

[shayzorblade]

This is what I get for not closely reading the calculator readouts. I could have sworn it say R19 /facepalm.

I'll look at the alternate options they listed; but the overall point still stands. Will I run into AWD system issues by running different diameter front from rears?

[shayzorblade]

Ok, re-calculated with a 255/35R19, also a very near match for the 225/40R19 (1.1" wider, -0.4% diameter, same sidewall, -0.4% circumference) which adds 1 rev per mile (at 90mph reading it would be 89.7mph in actuality).

[J555]

You really don't need to limit yourself to the Nokian, even considering your own good experience. While I respect Nokian as a very solid mid-class manufacturer, there are certainly better tires available in the desired size...

[Th3Walrus]

Originally Posted by shayzorblade

Ok, re-calculated with a 255/35R19, also a very near match for the 225/40R19 (1.1" wider, -0.4% diameter, same sidewall, -0.4% circumference) which adds 1 rev per mile (at 90mph reading it would be 89.7mph in actuality).

That is already the size that will be on the rear, so there would be no difference in diameter/circumference. You'd be running a square 255/35R19 setup, but the fronts would be on an 8" wide rim compared to the 8.5" wide rear.

Stop comparing the current front tire size to the new front tire size.