[BabyMcar16]

What is the widest tire I can fit on the stock wheels of a 2016 M235i? Stock tire size now is 225/40/18. Any help would be great.

[BabyMcar16]

Originally Posted by hwntime

Do you have the OEM staggered set up or squared? Staggered comes in 18x7.5 front and 18x8 rear so it really depends on what set up you have now.

They are 225/40/18 all the way around so I think they are the 18x8

[hwntime]

Originally Posted by BabyMcar16

They are 225/40/18 all the way around so I think they are the 18x8

225 will be a 7.5" wheel. Widest "recommended" is 225 but you can safely go up to 235. OEM 18x8" wheels come with 245/35/18.

[BabyMcar16]

Originally Posted by hwntime

225 will be a 7.5" wheel. Widest "recommended" is 225 but you can safely go up to 235. OEM 18x8" wheels come with 245/35/18.

So 235/40/18 will work then and have no fitment issues? I am really just looking for a little more in the grip department in the rear. I think 235 will do. Thank you for your help.

[hwntime]

Originally Posted by BabyMcar16

So 235/40/18 will work then and have no fitment issues? I am really just looking for a little more in the grip department in the rear. I think 235 will do. Thank you for your help.

I'm sure others will chime in on their set up. I'm staggered tires (225/245) on squared wheels (18x8) so I don't know what guys are doing with squared set ups for the narrower wheels. Best bet would be to check the inside of your wheels to make sure you know what sizes your wheels are. Did you purchase the car new and it came with 225 all around? If so, you definitely have squared 18x7.5 but if you purchased the car used, the previous owner could've changed tire sizes so you better check to make sure.

[BabyMcar16]

Originally Posted by hwntime

I'm sure others will chime in on their set up. I'm staggered tires (225/245) on squared wheels (18x8) so I don't know what guys are doing with squared set ups for the narrower wheels. Best bet would be to check the inside of your wheels to make sure you know what sizes your wheels are. Did you purchase the car new and it came with 225 all around? If so, you definitely have squared 18x7.5 but if you purchased the car used, the previous owner could've changed tire sizes so you better check to make sure.

I bought it new off the lot. It came with 225/40/18 all the way around.

[hwntime]

Originally Posted by BabyMcar16

I bought it new off the lot. It came with 225/40/18 all the way around.

Keep in mind the overall diameter of the wider tire. Your speedo will be slightly off. If you're traveling at 60mph, you'll actually be going 60.7mph. Not much of a difference but worth mentioning if you're going up to 235/40.

[BabyMcar16]

Originally Posted by hwntime

Keep in mind the overall diameter of the wider tire. Your speedo will be slightly off. If you're traveling at 60mph, you'll actually be going 60.7mph. Not much of a difference but worth mentioning if you're going up to 235/40.

I didn't think the width made a difference in the speedo. I thought it was with the sidewalk height. Like if I went from a 40 to a 45. Because the rotation of the tire would be longer or shorter if you won't with a 35.

[hwntime]

Originally Posted by BabyMcar16

I didn't think the width made a difference in the speedo. I thought it was with the sidewalk height. Like if I went from a 40 to a 45. Because the rotation of the tire would be longer or shorter if you won't with a 35.

The 40 is an aspect ratio. So the wider the tire, the taller that ratio becomes. Here is a description off of tirerack:

P225/50R16 91S

The 50 indicates that this tire size's sidewall height (from rim to tread) is 50% of its section width. The measurement is the tire's section height, and also referred to as the tire's series, profile or aspect ratio. The higher the number, the taller the sidewall; the lower the number, the lower the sidewall. We know that this tire size's section width is 225mm and that its section height is 50% of 225mm. By converting the 225mm to inches (225 / 25.4 = 8.86") and multiplying it by 50% (.50) we confirm that this tire size results in a tire section height of 4.43". If this tire were a P225/70R16 size, our calculation would confirm that the size would result in a section height of 6.20", approximately a 1.8-inch taller sidewall.

[hwntime]

Use this calculator for everything you'll need to know about diameter, cirmcumference, sidewall, speed, etc. https://tiresize.com/comparison/