[rdljr]

My CPO 328i Sport Line came with staggered rims, at least according to the door sticker. I noticed a few months after buying it that all my tires were 225/45/18, even though the rear calls for 255/40/18. I asked two service advisors at two separate BMW dealerships if this would cause any problems, but they said it wouldn't. Is this something I should be worried about?

Side note: I noticed when I'm driving at highway speeds, the speedometer is off by a significant margin (at least according to the "your speed" radars - cruise control set at 60, sign says I'm going 55). Would the rear tire size being off have anything to do with this?

Thanks!!

[328iX]

If I'd have to guess the last owner probably sold his stock wheels, and purchased another set prior to returning the car? What BMW wheels are on the car?

Yes a smaller overall tire diameter will cause your speedometer to read higher than you're actually going, but between 255/40/18 and 225/45/18 it's only a very small percentage. About 0.2%

For example on your current tires, the 225/45/18, when your speedo reads 80mph, you're actually going 79.82mph, and when you're going 60mph, you're actually going 59.86mph.

I have read online before that F30 speedometers are a bit off, but don't think it would be 5mph.

[rdljr]

It has the standard 397 18" wheels

[Desertnate]

Also keep in mind, BMW purposely builds in a margin of error into the speedometer. I think it's around 3%. Since the tire size currently on the car is an OEM, any deviation shouldn't be caused by wheel/tire size in this case.

However, that still won't account for a 5mph difference (almost 8%) between what you saw on the display and what is showing in the car. Have you checked your speed using GPS with an app on your phone?

[wdeerfield]

You'd have to pull the wheels off the rear and see if they are 8 or 8 1/2 width printed on the backside of the spokes. Most likely, like others have said, the original owner either sourced these just for lease return or just slapped the four tires on to not get dinged for tread on lease return.

as for the speedo. that sign could also be off as well and reading a little low. BMW with stock tire sizes reads 3% fast. if you upsize to 235/45/18 it will be very close to accurate

[Manny1994]

New on here figured I could post my question on this thread...I recently purchased a set of four wheels (Variant Xenon). All four are 8.5X19 and I wanted to know what the best tire size would be without compromising too much. Also did I make a mistake by purchasing all four wheels the same size? Vehicle is RWD.

[Desertnate]

Going to a tire size calculator like https://tiresize.com/calculator/ will help you compare OEM sizes to what you might want on your new wheels. The closest you can get to the OEM circumference the better.

Going with a square setup isn't really a bad thing. The car will rotate easier and be less prone to understeer. Even though I'm on narrower, soft, winter tires, my square winter setup makes the car feel more agile than my staggered OEM summer setup.

[Manny1994]

Thank you, appreciate the info!