Why OEM spec 19” front and 20” rear on M3?

[8262S]

Sorry, posted in wrong sub forum. I am reposting this to the G80/G82 forum. Original post is quoted below.

[edylcreyob]

Originally Posted by 8262S

Hello. I just did paperwork for a reservation slot for an M3CX and am hoping for delivery around March.

I intend to buy winter tires over the summer to not run into the availability problem that some here are reporting. Sucks to hear some of you are running into supply problems.

In researching tires, I read somewhere that the front tires was 19” to put more weight on the front tire, but can’t recall the source. Is that true? If not, why is it OEM 19” front and 20” rear?

I ask because I’m looking for a second set of wheels and am trying to figure out if I need to follow that OEM 19”/20” sizing.

I am on the fence of keeping the OEM wheels as summer wheels and getting a less expensive pair of winter wheels. Then the question is what size.

Alternately am debating using the OEM wheels for winter and getting a set of M Performance Frozen Gold Matt 1000 M wheels (20/21" Front/Rear) for summer. They would look incredible on a Dravit Grey M3. But when I looked for those wheels in the BMW individual configuration site it listed the sizes as 20”/21”.

I am happy with 19/20, 20/20, 20/21. Not sure I have a strong preference but know that I want to use the Michelin Pilot *BMW OEM spec tires long term as my summer tire.

I would like to understand why the tires are 19/20, versus 20/20, so I can intelligently make a decision. “It just looks cool” is probably not what the BMW engineers said. LOL. I watched the *BMW video and was amazed at how many tires they tested before arriving at the OEM spec. I would bet they out the same amount of work into wheel size.

And I did do a forum search but didn’t find any helpful threads. Sorry if I missed something relevant.

Thanks.

All I can tell you is 19's won't rub on the front part of inner lining of the guard at full lock but 20's most likely will depending on tyre size etc.

[RugbyBro]

This is a question for the G8X boards but based on the F8X CS, we can probably give some insight. The larger rear wheel theoretically and practically reduces sidewall flex (as there is less of it), and thus, the car's DSC is calibrated around the 20in rear. The car's EDC is calibrated with a staggered setup in mind. Can you run 20/20? Of course, make sure the front rolling diameter is within the acceptable range (as close to stock as possible), but you'll have a noticeably bumpier ride due to the decreased sidewall from the larger rim.

[8262S]

Originally Posted by RugbyBro

This is a question for the G8X boards but based on the F8X CS, we can probably give some insight. The larger rear wheel theoretically and practically reduces sidewall flex (as there is less of it), and thus, the car's DSC is calibrated around the 20in rear. The car's EDC is calibrated with a staggered setup in mind. Can you run 20/20? Of course, make sure the front rolling diameter is within the acceptable range (as close to stock as possible), but you'll have a noticeably bumpier ride due to the decreased sidewall from the larger rim.

Oh crap I put this in the wrong forum.

Can I moderator move it? Otherwise I will try to delete it (if that's possible?) or just repost in G80/82.

Sorry folks.