XSeries-forum

Hi everyone please can u give me some advise on what tyres to buy next for my x5 40d f15 I've got run flats on at the moment which have done 10,000 miles and the fronts are bald
Many thanks

Buy a set, not a pair.  Wide tread variance increases stresses on the transmission.

Buy '*' marked if you have a staggered set up - which the 40d will have.

Don't go cheap!

Recent, and increasing reports, of shattered differentials or transfer boxes are pointing at increased chances of damage where either only a pair of tyres have been replaced (resulting in wide tread depth variance), and where non '*' marked (made for BMW transmissions) have been used.  Staggered setups suffer far more than those where the tyres are the same size and rim size all round.  It is to do with the circumference of the tyre.  It must be within a few mm or the system 'winds up' and something breaks.

You can save money by coming off RFT, but stick with the correct makes as a broken transmission will cost you far more than you saved.  RFT seem to have poor service life too.

Unfortunately it means you are looking at £800+ for tyres if on a 20" setup like mine.  I don't know what you have on yours.

I'm certainly going to change all four I've looked at a few different makes Pirelli Goodyear continental etc I just wondered if anyone could recommend anything in particular
Many thanks

From personal experience the Dunlops the car came with were shorlived too.  Bridgestones on now.  Slightly better ride and seem to be wearing better.

I use Pirelli for the winter set and being 19" they are better....and longer lived.

All are RFT.  The X6 has no air suspension system but does have sport suspension.

Mine are 20 inch I don't know weather to go run flat or not & I'll be using them all year round
Help!!!!

Same as mine.  Non-RFT are reported as giving a better ride due to the softer sidewalls.  You can get a spare wheel kit from BMW (and probably via eBay too these days) for the 5-seater but there is no room to put one in a 7-seater meaning you need a reinflation kit.

It's really down to what you are happy to drive with.  No difference in grip between RFT and normal in my opinion, just a big price difference.

Some garages will still not repair an RFT, others will.  Bit of a lottery that one!

I still use RFT as mine is under warranty but I could go to normal I suppose.  The X6 lower boot compartment is too useful to fill up with a spare and I've only done 35k from new so cost not really an issue as I'm only one my second set.

Sorry to divers a little off topic but it is related to tyres,on my 56 X5 they came with the 20'' wheels especially the very large 325 rear tyres which are massive,but as the X5 is permanent 4 wheel drive  do all the tyres have too be of the same brand and exact same type of tyre model if that makes sense.What i mean by this as long as the tyre sizes are correct for my specific model is it all right to say have Dunlops on the front and Pirelli on the rear or must they all be say Dunlops,hope you understand what i am saying 

As on mine they are tubelss tyres but the front pair which are the same brand name but the rear 2 are a matching pair but a different brand name and was wondering if this is all right ??

As long as both are radials and they pretty much always are then it's OK.

Not ideal, but OK as long as the tread depth is broadly the same front/rear.  The issue is differences between the circumference of the tyres in use.  '*' marked tyres are matched sets from new so even with the different sizes front/rear, the actual circumferences are close.

What owners are finding is that if the tread depth, and therefore circumference, varies by more than a few mm things break!  They shouldn't but BMW have used a system with such fine tolerances that exceeding them can destroy a diff or transfer box.

On staggered sets we have seen a reported 32mm difference with a non '*' set even though the sizes are correct, and that will stress the transmission so that eventually it gives way.

It doesn't happen to everybody, but with cars getting older, premium tyres are an expense hard to justify and chances are taken in all innocence.  Sometimes it just is a bad call.

If you are hearing any unusual rumbling noises, or the car jerks at low speed on full lock then consider tyres yo be the cause.