XSeries-forum

Hi everyone,
I like to know if people have fitted aftermarket wheels to there X3. The reason being that I can get some wheels that are 8j fronts and 8.5j rear, they are 35et 18inch the tyre size is front 225 x 40 and rears are 255 x 35, are these ok or should I have tyres the same i.e. 235 x 50, hope I'm making sense.

Tyre sizes are wrong they are a car size not an suv.
What size are fitted at the moment.

Hi, at the moment I have 18" wheels with 235/50/18 tyres, thanks.

Correct tyre sizes are shown on the tyre pressure plate - often on the driver’s side B-pillar.

Or check (BMW parts database), or somewhere such as alloywheelsdirect.

I check BMW Database and 235/50/18 is correct.https://xdrivers.co.uk/forum/posting.ph ... =7&t=18663#

So the answer to your original question is that proposed wheel/tyre combination is wrong.

X3’s are VERY sensitive to tyres and picking the wrong sizes (basically anything other than BMW recommend and changing tyres as a set) can and has destroyed other members transmissions. The transfer box tends to be the point of failure. Staggered wheel sets are the vulnerable option.

Ideally you need to use only factory sizes and keep the tread differences to less than 1.5mm between any one tyre and the rest, or between axles. Tyres should ideally also be ‘*’ marked on the sidewall as these are the approved tyres. Unfortunately that means premium brands and therefore premium prices. You can get away with not using ‘*’ tyres but be wary.

BMW transmissions are not as well designed as they really should be, and for an AWD vehicle are too easy to break - especially with staggered tyres. It’s a problem that is common to those vehicles fitted with staggered wheel setups (not just BMW). If all four wheels and tyres are the same size then it is far less risky to use other makes of tyre. The fundamental cause is different rolling radii due to different tyre sizes causing ‘wind-up’ in the shafts and diffs. Eventually something breaks.