A star tyres , myth or fact

[ommis]

What’s the score with the tyres on the xdrive
BMW says run flats
German car specialists say different in my area
Transfer box will mess up says bmw
German car specialists say as long as tyres are same size as the ones your taking off . There isn’t a problem

Regards newbie

[Alan Gunn]

BMW recommend star marked tyres as the rolling circumference is the same.
None star marked might differ a bit and wind the diff up.

[X5Sport]

The tyre issue applies to all X cars with staggered wheel set ups.  If you don’t have staggered wheels then no issue.  If you do have staggered wheels then the transmission ‘winds up’ and the transfer box or diffs break.  It does it happen to everyone and as yet no hard a fast ‘rules’ about exactly which tyres are more likely to cause a problem than others.  Too many incidents on here for it to be myth.

You definitely don’t need runflats though, and BMW even offer a non-runflats version on many.  Have a look at Realoem and you will find options the factory uses.

German car specialist doesn’t mean they know enough about xDrive transmissions.

[ommis]

When you say staggered wheels
I have 20s all round
But the fronts are narrower than the rears
So am ok then to go with out the run flats

[Graeme]

Suggest you write down the sizes of the front and rears presently on your wheels.  Mine are 255x50x19 107V* runflat on the fronts, 285x45x19 111V* runflat on the rears - all Good Year Eagle F1.  Yours will be different figures but in order you need the width, height, diameter, load and speed ratings. Then check with the various on-line tyre suppliers for * marked non runflat in your size, load and speed specifications. Also, it is important to have the same make front and rear. As there is no spare wheel, you'll need a large enough inflation kit  (cans of Tyreweld + pump) for the big rear wheel.  I'd be surprised if you can find * marked non runflat tyres for your staggered 20" wheels with the load rating you need but let us know how you get on...
Graeme

[Spandex]

Has anyone managed to find any actual evidence for the two claims involved in this:

1. Star rated tyres have identical sizes across staggered setups.
2. Non- star rated tyres are different enough in size that they cause transfer box issues.

I know there is anecdotal evidence, but I’ve not been able to find anything conclusive. I’m looking for something more than “my box failed and I had non-star rated tyres”.

[ommis]

Is there any one out there.
That has actually used non rft.
And is alive to tell the tell
Eg . Transfer box still intact. Gear box whine. Etc etc
The German specialists say they have changed many a tyre and been no problems
Are people confusing the x3 problems and tarring the x5 with the same brush

[PhilUK]

I have staggered 20s on my X5, recently fitted non run flats (don't think they are star rated) and I now sometimes get traction warning light and cut in power when cornering  :'(

Will be going back to run flats next week  :-[

[Pat Mustard]

I'm on my 2nd E70 and always run on normal tyres rated at 111 and have never had an issue . In saying that I don't have staggered setup anymore. Car drives way nicer with 4 x 255 x 50 x 19

[asoni]

Very interesting thread as this has confused me as well.

I was considering non run flats. I understand * system, however Bridgestone seem to do the exact same dueller h/p in the non run flat option in exactly the same sizes. Therefore surely the overall radius must be exactly the same as well as the tread pattern.

Even on a staggered setup, how could this cause any potential problems?

[X5Sport]

[quote="Spandex"]
Has anyone managed to find any actual evidence for the two claims involved in this:

1. Star rated tyres have identical sizes across staggered setups.
2. Non- star rated tyres are different enough in size that they cause transfer box issues.

I know there is anecdotal evidence, but I’ve not been able to find anything conclusive. I’m looking for something more than “my box failed and I had non-star rated tyres”.
[/quote]

One of the members on here found a 32mm difference in the circumference on a non ‘*’ marked set which was causing wind-upand grinding noises.  Tyres changed to ‘*’ marked and no more problem.

[ommis]

Confused
Staggered tyres , if all 4 of them are 20s . Surely the rolling circumference is the same on each corner of the car
If it’s that critical on tyre size .
Why doesn’t the transfer box get wound up as the tyres wear . Front near side always first to go because of roundabouts
What about wheel spin surely  that throws transfer box out of sync
General driving inside wheel goes slower when cornering isn’t that why there’s a diff fitted to the car
Again the rolling circumference must change. Because isn’t one wheel going faster than the other ,then both wheels match up to the same speed on the straight
Can’t see how the width of the tyre can pose a problem to the rolling circumference

[Icicles]

I have the staggered 20" wheels
And now running non run flat tyres, won't be going back to run flat tyres any time soon. More comfortable etc.
They are not star rated
I did heaps of reading, nearly did my head in. It hurt.
What I believe is the case, all run flat tyres with the star are bmw approved. BMW would not probably approve non run flats so tyre manufacturers don't put a star on them. I did not manage to find non run flats  with a star mark!
As discussed I have seen a lot of tyres from manufacturers where they have two identical models, one run flat and the other non run flat. I cannot believe for a moment that the star marked tyre would have a more accurate diameter. I'm talking your main stream manufacturers here. I would not comment on the cheap tyres.
When searching for tyres the cheapest to the dearest, $125-$1287 per tyre for a rear 315x35x20

Nons for me

Chris


Sent from my SM-G930F using Tapatalk

[Horizon]

[quote="ommis"]
Confused
Staggered tyres , if all 4 of them are 20s . Surely the rolling circumference is the same on each corner of the car
If it’s that critical on tyre size .
Why doesn’t the transfer box get wound up as the tyres wear . Front near side always first to go because of roundabouts
What about wheel spin surely  that throws transfer box out of sync
General driving inside wheel goes slower when cornering isn’t that why there’s a diff fitted to the car
Again the rolling circumference must change. Because isn’t one wheel going faster than the other ,then both wheels match up to the same speed on the straight
Can’t see how the width of the tyre can pose a problem to the rolling circumference
[/quote]
The profile of the tyre i.e. 35 profile is a percentage of the tyre (35% of the width ) 40 profile = 40% of the width
2 wheel drive, no problem, you could put any size on each axle no problem, as for across an axle ( left to right ) this again is not a problem as the diff is designed for one wheel to travel further than the inside tyre on a turn.
If you locked the diff you can not turn around a corner without putting maximum strain on the diff, people accept this.
It's the owners choice to what tyres they fit, it's their risk.
I've had first hand experience of buying an Xdrive car with non star rated tyres and have seen and felt the transmission winding up , and lurching at slow speeds.
I opted for 4 identical tyres instead of the staggered  setup and the results were immediate.
Some makes are more forgiving, others are miles out.
I've even checked the manufacturers tyre size data sheets which give the rolling circumference of their tyres and on different profile tyres in the same diameters I.E. 19/20" range the figures can be around 150 mtrs per mile difference.!!!!!!!
That is replacing like for like tyre sizes.
Tyre buyer beware

[Spandex]

[quote="X5Sport"]
One of the members on here found a 32mm difference in the circumference on a non ‘*’ marked set which was causing wind-upand grinding noises.  Tyres changed to ‘*’ marked and no more problem.
[/quote]
Ok, but that isn’t evidence of either of the two points I posted, not to mention it still falls into the ‘anecdotal’ category. Also, we don’t know what difference, if any, there was between the front and rear star marked tyres he put on, and we don’t know if changing for a different set of non star marked tyres would have also fixed the issue (i.e. if the issue was something wrong with the tyres he had on, unrelated to their rating). Basically, it’s not enough information to make any kind of judgement either way.

I’m not saying it’s a myth (or that it’s not), but I’m just surprised that there is no hard evidence available if it’s so cut and dried.