RFT TYRES , a cheaper alternative ?

[MarkG_M3CP]

Indeed general advice is to never mix tyre types on a car and manufacturers on an axle. The former is due to difference handling capabilities as you wouldn't want a super sticky front end and no rear end grip! The latter is supposedly to save the axle/diff/trans.

But then... on my 335 xDrive I swapped to non-RFT, non star marked Michelin Pilot Super Sports and covered 60k+ hard miles on them with zero issues (unless you count better handling, better ride and no side wall bulges and issue).

BMW use PSS for the M Cars yet even now they sometimes use Contis.

Of course the X5M has PSSs too so they may be an exception to the rule - but I doubt it.

Incidentally, never has any warranty work refused on the 335. Even with ACS aftermarket springs they covered a failed adaptive damper. I did record a discussion with the dash cam where someone noticed the 'wrong' tyres but another advisor said they were fine!

All in all, inconclusive. I think I'll switch to Dunlops next as they won't be quite so soft.

[kkx5]

I  dont get all this bla bla bla ... why take the risk when the knowledge is out, just read other forums. We have moved to hi-tech AWD system (xdrive). Keep tyres as bmw says and the problem with diff, transfer, gearbox doesnt exist...

[allforus]

After speaking to BMW the problem is created in the main by a mismatch h of tyre diameters on the same axle where the transmission tries to compensate for one wheel spinning faster than the other therefor applying what ever braking effect etc thus loading the axle up for long periods of time

It was also an issue in early models where tyre brand had a huge effect on the transmission as well

Just some insight from my Bmw dealer

[Nat]

Hi,

You are refering to axle wind as it was known.
I had a grand cherokee back in the day and on full lock / slow manovers you could feel a wheel " hop " as it unwound itself.
I guess it makes for interesting engineering...........every time you turn the outside wheel will always travel further than the inside one.............the car should be engineered to deal with that.

What if you drove your X5 every day and only turned right. Would your transmission fail ?

As for the coment of just sticking to the BMW recommended tyres ,I hear you , but the  £400 difference in price for a complete set of tyres that you could have ,  thats quite a lot of money , which makes buying a different tyre brand a compeling proposition for those on a limited budget.

Regards
Nat.

[gmc15]

Does anyone actually know what makes BMW '*' marked tyres and Merc, Audi, Porsche marked tyres different from other non marked tyres? I have been looking into this and no one can actually say what makes a BMW tyre different from any other!
I wonder how many transmission failures are actually down to the tyres or is it just poor engineering on the cars.

I run '*' marked tyres on my X5 but have non '*' winter tyres on it now.

[Graeme]

I'm told, but it is only hearsay, that the "*" is an approval by BMW that the circumference of new tyres is within an acceptable limit.  I understand this to be important for the transfer box and differentials , especially where the front and rear tyres are different sizes, e.g. 255 x 50 x 19 on the fronts and 285 x 45 x 19 on the rears so the circumferences of each is similar. I too have "*" summer tyres and non * winters for life in North Yorks and south west Durham!  They've been fine for the past 3 years. 

Graeme

[sid10]

I watched a youtube advert for BMW today about star rated tyres done in 2011 which hopefully will put this to bed as it explains that one of the most important parts of the development of the car is the tyres and how the car performs on and with them . They spend millions on development and will only star rate tyres that have been tested , pass the stringent tests that they do and give the car the performance that the car and owner deserve . anything less will effect the whole experience .
    At the end of the day you buy a car that you want & have high expectations ,  I was admiring a 2  years old BMW M3 a few weeks ago , obviously loved by its owner in fantastic showroom condition , but checking the tyres I was shocked that it was running on Accelera tyres . Why would you run an M3 on these ?
a. Save a few quid .
b. No nothing about safety or performance tyres .
c . Thought they looked good .
d. Put them on to sell it .
e. Only ever drive at 40mph .

[X5Sport]

f.  Idiot

[sid10]

Never thought of that !  )