[F30_328i_uk]

Hi,

Got 19in 403m wheels (225/40 front, 255/35 rear) with run flats, but they're due for a change now. Going to go with go flat mps4s's, so I'm quite excited about the comfort/noise improvement over the eagle F1 run flats.

Going to stick with the same size in the rear but read in quite a few places online that people tend to change the front tyre width/profile to 245/35.

It's now 2024 and the last thread I read on the subject is a year or two old.

Is there a general consensus on whether or not this is a good move?

If it decreases understeer, that's a positive. However, I do not want to sacrifice comfort and road noise.

I'm also slightly worried it'll produce too much forward rake on the geometry and produce too much wheel gap to the arch. I've seen the comparison photo in *this thread* many times but not sure if there's much difference?
Last thing I want is the alloy/wheel looking too small in the wheel arch.
I'm RWD, so xdrive is not a concern.

I'm also concerned if it'll affect the speedo too much - I've read conflicting info stating that speed is taken from an average of all 4 wheels via ABS.
I've also read that it is taken from a single wheel speed sensor in the rear.

Any thoughts and opinions on the subject? I'm not averse to sticking to stock sizes at all but just wanted to put it out there before I commit to purchasing.

[visionaut]

The 245/35-19 fronts are a great improvement all around on the OE 19” staggered wheels. Traction, handling, braking, cruising. The 225s are undersized and were spec’ed for mileage. (3-series have run a 225 front tire width going back multiple generations - but power and weight increases… hmm.)

Being bigger improves comfort.
Road noise is mostly a factor of tire model/tread design.
The diameter is the same (~1% so it also works for AWD) as the 225, so sidewall heights aren’t noticeably different. (Even tho it’s a 35 aspect ratio it’s based on a 20mm wider width, so equates to a 40 aspect 225.)
Speedo will also be same, again since similar diameter.
Facts don’t need to be updated to remain true.

Only negatives might be faster tire wear, slightly less mpg, and increased mileage on the car because you like to drive it more…

[danb1979]

Originally Posted by F30_328i_uk

Hi,

Got 19in 403m wheels (225/40 front, 255/35 rear) with run flats, but they're due for a change now. Going to go with go flat mps4s's, so I'm quite excited about the comfort/noise improvement over the eagle F1 run flats.

Going to stick with the same size in the rear but read in quite a few places online that people tend to change the front tyre width/profile to 245/35.

It's now 2024 and the last thread I read on the subject is a year or two old.

Is there a general consensus on whether or not this is a good move?

If it decreases understeer, that's a positive. However, I do not want to sacrifice comfort and road noise.

I'm also slightly worried it'll produce too much forward rake on the geometry and produce too much wheel gap to the arch. I've seen the comparison photo in *this thread* many times but not sure if there's much difference?
Last thing I want is the alloy/wheel looking too small in the wheel arch.
I'm RWD, so xdrive is not a concern.

I'm also concerned if it'll affect the speedo too much - I've read conflicting info stating that speed is taken from an average of all 4 wheels via ABS.
I've also read that it is taken from a single wheel speed sensor in the rear.

Any thoughts and opinions on the subject? I'm not averse to sticking to stock sizes at all but just wanted to put it out there before I commit to purchasing.

You could go 235/40 and see how they fair; or as you said 245/35

Have you looked at the tyre calc on willtheyfit.com - that's a good tool to see how they compare; also gives you the specs and whether they're in the 2.5% +/- specs etc

It'll be much better on the non RFTs too