Originally Posted by quality_sound
Ben - Question regarding sizing. I know BMW recommends a square 235/40/18 setup (which I'm fine with) but this is almost an inch shorter than OEM rear so it'll hurt mileage as well as add phantom mileage. A 235/45/18 is .02" taller than OEM rear while maintaining the 235 section width as recommended but is roughly .75" taller than the OEM front. Would there be any problems running this size in the front? Any reason this isn't the recommended size, other than it being slightly larger than BMW's recommendation?
The only real snow I have to deal with is a few unplowed roads before I get to the priority and B roads before I get on the Autobahn. The priority and B roads and the Autobahn are all plowed regularly. Once I'm on base everything gets plowed eventually but then we only have a 50kph limit. Would a staggered setup be ok, or even preferable?
My M won't be here until mid January so I have a little time left before I have to buy but I want to consider all my options first.
Nothing wrong with the 235/45R18 that I can see. Given that the car does not need the height stagger to work correctly (some do, esp in regard to traction control, but the BMW doesn't seem to care) it is extra complexity for not a whole lot of gain, but there's nothing to say you can't do it.
Fuel mileage would not make the decision for me, as the difference there would not be very great. Phantom miles, maybe, but a couple percent over the course of a few months is usually not a big difference. If you feel like it's worth the trouble though, I do not think there would be any major downside other than perhaps fewer tire choices in matching pairs vs all same size.