Tyres front/rear different query.
 

A 2015 BMW Active Tourer 225i XDrive.
In a 'norma'l world I would just replace all four tyres together but will it be OK to leave the oem summer Bridgestone run flats on the rear wheels and put Bridgestone All Season run flats on the front only ? I will do the rears later in the year.
Cheers
Brian.

These use a Haldex rear diff system like the Mini it's based on (as well as VAGs and Volvos etc), so 'probably' not as prone as the traditional xdrive systems (BMWs with a longitudinal engine/box). As the system spends most of its time disengaged.

That said it's the tread depths that aren't ideal if you are using brand new 8mm tyres on one axle with, say 3mm tread on the other, when the system does engage it's going to see more wind up. And essentially that's more wear on the clutch inside the rear diff and more strain on the transfer box.

If you do ever feel a shudder or lurch when pulling away or feel the front tyres 'jump' or scrub whilst manoeuvring in tight car parks stop driving the car and get matching tyres fitting ASAP.

Maybe worth asking on Mini forums as the R60 Countryman All4 uses the same system (although I know many mini drivers will drive with dash warnings lit up like a christmas tree and worn ball joints that rattle constantly and still not think anything is wrong :lol1: ).

Many thanks for the very helpful reply. Things have moved on somewhat as it appears that All Season run flats are not available in the required size 205/55/17 so I will now change all four together to normal All Season tyres and chuck a space saver in the boot.
Cheers
Brian.

Personally, if I was going to change them, I'd also ditch the runflat tyres altogether.
Standard tyres are not only cheaper, but the difference in the ride quality is night and day.