A star tyres , myth or fact

[graemeX5]

Hi

Try this link it will show you the difference in the circumference of different wheel and tyre combinations and is helpful.

https://www.willtheyfit.com/index.php?width=255&aspect=50&diameter=19&wheelwidth=9.5&offset=35&width2=285&aspect2=40&wheel_size=20&wheel_width=9-5&offset2=35

Graeme

[Spandex]

Just one comment to above pictures: As long as some of You will question star marked tyres, i will have a job:)
The knowledge is there for many years. Buy cheap tyres, pay high diff/gear/transfer box bills. If you can not afford to pay £900 for set tyres on high tech 4x4 BMW, go and buy a ford fiesta....

The reason some of us will continue to question star marked tyres is because people like you post unhelpful nonsense like this. There was absolutely zero useful information in that post, but let’s break it down so you can address it properly.

1. You haven’t commented on the pictures above. We still don’t know what they’re supposed to show.
2. Cost is irrelevant. There are expensive tyres which are non-star rated. There are (relatively) cheap star rated tyres.
3. if the knowledge is ‘there’, then please help us out and post it here. It would be really helpful. What isn’t helpful is repeating anecdotal evidence that has huge logical holes in it.

As I’ve said, star marks on your tyres doesn’t mean they’re within tolerance for their whole lifespan, so it simply can’t be true that star marked tyres never cause issues. Or, the tolerance is much bigger than is being stated here, in which case it would be useful to know what it really was so people could make informed decisions when buying tyres.

When people repeat a mantra like “buy star rated and you’ll be fine”, it just makes me think they don’t really have any in depth knowledge at all.

[CondorX5]

My E70 40d has had only * marked tyres and has been under BMW warranty all its life so far, but that didn’t stop the transfer box knackering itself - posted about it on here. Covered by warranty and yes, they did go through the whole tyre thing and if they had not been *marked there would have been an issue.  tyres all star marked so no issue.

So the transfer boxes can give up even on a car with * marked tyres.   My reason for buying star marked is down to the warranty issues if I don’t.

Plus the diff has just been replaced on the recall. 

[Pat Mustard]

Anybody ever question who actually makes those transfer boxes ? I know the earlier E53 ones were made by ATC and weren't the best either when they came under a bit of pressure. Just like the self destructing Chrysler E53 auto boxes that were  made under license in France. It's too easy to blame the poor old tyres for everything.

[X5Sport]

Later ones still have an ATC code if that means anything?

[Pat Mustard]

ATC is the GM acronym for active transfer case. If this be the case those E70 transfer cases look like being out of the General Motors stable and that certainly wouldn't inspire confidence . Could be completely wrong of course. The single bigest question  is how much of our trusty steeds is actually made by BMW ?  Every single little part you take off is from Mexico, China , Spain etc. Just Meccano at the end of the day and when something goes wrong just blame the other fella.

[A Blair]

I had the same thoughts as spandex. I still feel its a swizz.
Put some chalk across the tyres and measured real rolling road circumference. Happy about the tolerance.
I have frequently thought about writing to those Dutch guys Vredestein. I now feel inspired.

[Spandex]

Just to be clear, I’m not really questioning the idea that tyres of differing diameters could damage a transfer box or diff. I have no doubt that’s the case. What I would really like to know is how different they need to be before it’s an issue - because it’s entirely possible that there are plenty of tyres out there that aren’t star marked but are well within that tolerance. It’s also entirely possible that excessive wear on one axle could push a set of star marked tyres dangerously out of tolerance.

That’s why I get a bit annoyed by people repeating generalisations and confusing correlation with causation. It tricks people into buying things they don’t need to buy and, worse, it gives people a false sense of security.

[graemeX5]

Hi

I would think somewhere in the technical information for the BMW there is a mention but I know when Horizon had his original set up of staggered on his old X3 that was approx 1.1% difference in the circumference and that was the recommended set up from BMW. See link below.

https://www.wheel-size.com/calc/?wheel1=235-45-19X8.5ET40&wheel2=255-40-19X9.5ET40&fcl=50mm&scl=50mm&wcl=30mm&sr=0mm

So if BMW recommends that and it's 1.1% out then that is okay,but how far it can be out before it causes probs I haven't found as yet.

Given that the tyres will wear over time and if they were the same make then they should wear at a similar rate you should be okay, but Bmw recommend you change the tyres as a set, I assume to avoid problems. So if you change say two tyres to brand new ones then I think that could cause probs due to the difference.

 I will have a look in the X5's handbook tonight to see if it's mentioned there
Graeme

[IanP]

All the handbook says is to fit star rated tyres as  these have been recommended by the manufacturer. Differing tread patterns or manufacturers maY affect the DSC or ABS.

Simplest way to test  the theory is to put whatever tyres on you want, and let us know how you get on...

Everytime I changed the tyres on my 4.6 it cost 1/3 the price of the truck 

[Spandex]

So if BMW recommends that and it's 1.1% out then that is okay,but how far it can be out before it causes probs I haven't found as yet.

Yeah, the problem is, BMW can happily 'recommend' something that is miles away from the actual threshold because a) they just need to cover their arses and b) they don't mind being ultra-cautious because they're not the ones paying for the tyres. Whilst I'm interested in their recommendations, I'm also aware that they won't ever give us the full story.

All the handbook says is to fit star rated tyres as  these have been recommended by the manufacturer.

The trouble is, I'm pretty sure BMW say that in every handbook for all of their cars regardless of which wheels are driven. All the other 'luxury' marques say the same about their own manufacturer-rated tyres too.

Simplest way to test  the theory is to put whatever tyres on you want, and let us know how you get on...

That's the method I'm hoping to avoid by finding out out if anyone has some actual facts regarding requirements/specs for star marked tyres, or actual tolerances for the x5 drivetrain. And even if that information simply isn't available, I think it's important to be clear when people ask for advice. Simply telling everyone who asks that they have to buy star-marked or risk their transfer box exploding isn't helpful.

[asoni]

I may give non run flats a go as I’m not convinced by the arguments.

I don’t think the issue is that tyres have to be run flats. I think it’s more they have to be a certain radius and have to maintain close to that radius.

As long as the tyres I buy do that, I really can’t see what problems there would be.

Cost is not an issue befor anyone pipes up, I’m happy to spend same money as run flats would cost.

I had a m3 before this and even with its much firmer suspension, it didn’t jar as much as the x5 when going over pot holes at speed. It’s ridiculous and I can only assume it’s the run flat tyres.

[graemeX5]

Hi

Here is a helpful link to you tube that I found which explains how the 4x4 systens work and the problems that are associated with the system and it also occurs where you have tyres which are too different in their circumference.
I couldn't believe the propshaft pic

https://m.youtube.com/watch?v=mhTVQh7bFtw

I've still not found the level of tolerance that a BMW can accept but did find a downloadable handbook for the X5 E70 on a website -tried the link and it doesn't work

In their day the old Vauxhall Calibra Turbos used to knacker up their 4x4 system when the tyres were just change in pairs rather than a set of 4 and thatswhy so many were converted to

Also found this link which explains about the tyres and the basis of why. You need matched tyres.

https://www.souzastireservice.com/tires-101/tire-matching-awd-4wd.aspx

Graeme

[graemeX5]

I may give non run flats a go as I’m not convinced by the arguments.

I don’t think the issue is that tyres have to be run flats. I think it’s more they have to be a certain radius and have to maintain close to that radius.

As long as the tyres I buy do that, I really can’t see what problems there would be.

Cost is not an issue befor anyone pipes up, I’m happy to spend same money as run flats would cost.

I had a m3 before this and even with its much firmer suspension, it didn’t jar as much as the x5 when going over pot holes at speed. It’s ridiculous and I can only assume it’s the run flat tyres.

Hi

You can try non run flats but it may also be worth checking your insurance co as they may require them, and may use it as an excuse  in the event of the claim, other companies will be okay.

I had a 1 series a while back and at the MoT they remarked on the rear tyres were not runflats and said it could affect the handling as the set up of the car was based On the car having the harder side wall of the run flat tyre.

On my last E53 I have same size tyres all around and no probs, again with thestaggered set up as all four tyres were new no problems.

However others have had probs where the difference is excessive but I still can't find what the figure may be but if you run a matched set then your less likely to have probs

Graeme

[ommis]

Does the four wheel drive system
Drop off the power / drive to the front wheels when the vehicle goes above a certain speed
I am sure my old e53 used to do this at 60mph
Will my e70 do the same
And if so surely that will stop the transfer box from winding up. If there’s on power going to the rear wheels