This is my 1st post after only just buying my 1st x1 and joining this forum.

I'm really pleased with the car (a 2012 20d automatic)

The wheels are 17in with 225/50×17 tyres but they are looking tatty.im looking at swapping them and there deems to be a lot of 18in wheels out there,and I'm wondering if 225/45×18 would fit ok as I read you need to be within 1% rolling diameter so as not yo affect x drive.

My pcd is 5x120.

Also  I've noticed a noise not dissimilar to a bearing noise at 50mph,it doesn't seem to be bearing though as it feels ok on the jack and when cornering and loading the bearing up it doesnt alter the sound 

Afternoon Jeff

Welcome to the Forum 

Take care when changing wheels/tyres 225x45x18 were in fact a Factory option for your car so should be fine are they BMW wheels(tip If buying a set complete with tyres make sure wear rates are even) Be aware that 18" and 19" wheels were also offered as a Factory option in staggered sets (wider rears) tyre sizes then became Front 225x45x18/19 Rear 255x40x18/19 If choosing a staggered set allow for new tyres would be my advice to avoid issues 

As for your bearing noise does it increase with engine speed or remain constant ? I would check the rear prop shaft centre bearing 

Enjoy your Beemer 

Dave

Thanks for replying dave,and confirming tyre size. 

I have just been out in car...I will check prop bearing...the noise doesn't alter with revs it just appears at 50...I folded drivers mirror in and got wife to do same on passenger side and it seemed to quieten down, so I'm wondering if it's the big mirrors in the wind