Okay folks who have made the switch on the F-platform from 17" wheel to an 18" did your ride quality improve or did it get worse?
I have a F55, 4 door S JCW tuned

I am on the fence as to what size to go with. My goal is to get the best possible ride possible with the stock DDC suspension and 25mm rear sway bar. the car is a daily driver in the Northeast and I don't want to get beat up driving it every day.

Heres what I am thinking for overall tire sizes
215/45/17
225/40/18

Which will yield a more comfortable ride? And I will be going from the OEM run flat to a traditional non-run flat tire, so I will get that improvement right away.

Thanks

 

215/45R17 with the additional sidewall would be the better riding of the 2, if we were comparing the exact same tire in those 2 sizes.

 

Thanks Alex
What are your thoughts on running a 225 wide tire on a 7.5" wide rim? Michelin's spec say the tire will fit a 7.5" to 9" wide rim. I am a little concerned that the 7.5" is at the bottom of the width range. Would I be better off with a 8" wide wheel, that way I am in the middle of the range?

 

I run 215/45-17 on a 17X8" rim.

 

You want tire to match wheel size/width for a perfect fit to get the most out of tire wear and performance/handling.

You compromise when you are at the extremes of what will fit or almost fit but it will still work. An extra wide tire on a narrow rim will force the wide tire to be pinched once mounted resulting in a tire that is less wide due to the constraints of the wheel width. The forces on the sidewalls and tread shoulders will be different than if it were a perfect fit as designed by the tire company. It's not a big deal if you only do street driving and don't push the tires but you might notice additional/uneven wear.

8" wide wheels are wider than OEM for the MINI which is limited to 7" wide wheels or less. This can affect the wheel and tire fitment and reduce clearance and increase risk of rubbing depending on wheel offset and drop in suspension. Wider wheels and wider tires usually weigh and cost more. Your choice. For daily street driving more weight is not that big a deal but less weight will feel more responsive, brake and accelerate better.

Ride quality has to do with the individual tire you choose, some are excellent on ride comfort and street manners. Secondary is always tire size, a bad tire in the right size isn't good. I shop of tires to suit my purpose first then ask if it can come in a size that will fit my car/wheels.

Too many owners look at size first but there can be alternative sizes that will still fit and work well for your requirements.