Tyres

[Thesisqokid]

me again, so only having rear wheel drive what are peoples thoughts on having star rated tyres on the and non rated on the front aslong as all fresh and within 2mm of each other. Has anyone had any good experience on non star rated?

[StuBeeDoo]

I've been using non-star for roughly 30k miles with no problems so far. Initially Avon ZX7, then Michelin CrossClimate +. I bought them new, and in full sets.
But....... mine are all the same size. I wouldn't recommend trying it if your car has wider rears.

Personally, knowing what the potential outcome could be, I wouldn't fit less than a full set even if there was less than 2mm difference. Yes it's costly, but that's what you buy-into with any premium 4wd car, not just BMW.

[Thesisqokid]

All wheels are square just someone removed the front prop at some point in its life and until i build up some more funds im not going to look into why yet. Il will replace all 4 all same brand as at the moment it has 3 of one brand and one different and unfortunetely the odd ones are on the driving wheels

[wizard-58]

hello I have read lots of posts on this tyre issue ..and really am confussed i have a square set up on my 2007 2.0d .at present on the rear i have 1x michelin latude sport 4-5 mm tread ..1x auto grip p308 again with 4-5 mm tread .been on car since 2016 when i purchased it ..both of these were on the front for over a 6mths .. the rears were down to min tread as in last MOT advisory bothfronts were on limit so moved to back and placed aforementioned on front .during winter months i have a spare set of wheels and tyres 245/65/17 which i used till april .then i went back to the summer set i replaced both of the worn ones with 235/55 r17 APLUS A607 budget line tyre which as new matching pair i had fitted on the front and the 2 aforementioned back on the rear. bit long winded but to sum up i have 2 miss matched rears similer wear and 2x matched budget on the front .that has been like that since april .I have done 1500 miles since then with 1 trip of 350 in one day and i have had NO transmission issues at all .. at one point i had 2 front tyres with 1.6 mm of tread ( mot advisery) and the 2 odds with nearly 5 mm.and then the other way round (1.6 mm on rear ) mine is one the first face lift .would this be why ??

[X5Sport]

Not sure what you are asking? Although the X3 is AWD it is predominantly rear-biased so rear tyres may wear out faster although in my experience front to back wear is balanced. This has been my experience on an X5, X6 and 2-series GT. even our ŠKoda Superb AWD had even wear. In your case the issue of different wear rates will be down to the different tyre compounds due to different manufacturers. This is a main reason not to fit mismatched sets.

There is no guarantee that having mismatched sets will cause any issues, it is just that based on owners experiences, along with those of a member kkx5 who fixed the results, the chance of a transfer or diff failure rose significantly (and expensively) when either mismatched manufacturers or tread variances if more than 2mm were present. Almost every failure reported involved tyres - and across all xDrive models up to the G-series when a new system was introduced. The issues affect many brands of ‘performance’ models with staggered wheels fitted. It is less of an issue with ‘square’ setups but not completely gone, hence the 2mm difference still stands as outlined in the BMW Technical Instruction System (TIS) used by dealers - but not mentioned in Owners Manuals

[Thesisqokid]

Basicly the front prop had been removed by previous owner and the reason is unknown to me why, i have a horrible clunk from the gearbox and think it has sometjing to do with the reason, i dont know if transfer case is shot or working hence why i say rear wheel drive.

[wizard-58]

hi sorry was not trying to be difficult i was just explaining what i have on my vehicle as I have come to learn after 6 years with a bmw NO 2 are the same.but i was wondering if after the face lift 2006/7 they changed the software so that the system isnt so sensitive to makes of tyres as long as they are matching wear across axle and of resonably good quality .

[StuBeeDoo]

..... changed the software so that the system isnt so sensitive

It's my understanding that it's the hardware/general design that causes the problems. If it could be worked-round with software, someone other than BMW would have done something about it years ago.

[X5Sport]

As above, it’s a hardware issue and affects many other makes of car. If you want performance you need tight tolerances. Whenever you fit different tyre size combinations (largely for cosmetic rather than performance gains) you introduce mechanical loads into the overall system. The way of controlling those mainly falls to specifying the tyres. Approved tyres have matched rolling radii and the construction/compounds used keeps changes of the tyre size at all speeds matched. No additional stresses are introduced. But, fitting different tyre combinations or makes or versions removes all of those ‘known’ controls and introduces ‘unknowns’ which the hardware manufacturer says aren’t a good idea and don’t design their systems for. Add restrictions from manufacturers who buy these transmissions imposed by the companies like BMW/Merc/Audi etc around costs and weight and eventually something has to give if the envelope gets pushed a little too far.

I believe that only the vary latest G-series transfer box has enough tolerance to cope. OK membership with those cars isn’t as large in the forum, but generally I have seen far fewer reports of broken transmissions on the newer ranges. Our 2-series Gran Tourer was fitted with a Haldex drive system rather than the standard ‘xDrive’ hardware as it’s predominantly FWD biased. We had to be careful with tyres on that too, same with our Škoda Superb 3 Estate AWD. They had ‘square’ setups but still came with a warning about tread depth.

20 years ago I managed a fleet that had 20+ Mk2 Discoveries and we had no end of trouble with transfer boxes and always changed tyres as full sets.

[Thesisqokid]

Hi all, just to update i went for 4 yokohama c.drive 2s there getting delivered today and i will fit them next week, so we shall see if they are any good.