[Leem40i]

Okay so you've gotten advice to replace all four tires because you got a nail in one?. First off unless the front tires were pretty much worn out you don't necessarily have to replace the two fronts. Secondly. Putting new tires in the front and not on the rear is absolutely not an issue. The tolerances for the Xride system is not that tight to wear the simple range in diameter that a tire has as it wears out will make a difference. Anytime you have a staggered setup you are typically going to have to replace one set uf tires before the other.

[avi66]

Originally Posted by Leem40i

Secondly. Putting new tires in the front and not on the rear is absolutely not an issue.

Actually it can be an issue with fitting here i.e. Costco.

"INSTALLATION OF LESS THAN A FULL SET OF TYRES

When a member does not replace tyres in full sets, Costco's tyre fitting policy is to position the new tyres on the rear of a vehicle. This policy is consistent with the direction given from all the major tyre manufacturers and tyre industry associations. Safe vehicle operation is the driving force behind this policy. A few vehicle manufacturers have wording in their owner's manual stating that new tyres should be fitted to the front of a vehicle. Mechanical issues are the driving force through this direction. This direction conflicts with the Industry & Costco’s safety policy of when only 2 tyres are replaced, that the new tyres must be fitted to the rear of the vehicle. The conflict here is safety versus mechanical. When replacing 2 new tyres only on the front of a vehicle, this makes the vehicle unstable and susceptible to sudden lack of stability and over steer. This creates a safety hazard not only for the passengers and driver in the vehicle but it also creates a safety hazard for others who may be harmed by an overturned or fish-tailing vehicle. A members request to sign a waiver of liability for the installation of replacement tyres only on the front axle will be denied by Costco."

[lfdal54]

Pulled this from ISTA

"General:


•The tyre size, manufacturer and tyre tread must be the same on one axle


•To meet the BMW standards, the vehicle should be equipped with tyres from the same manufacturer and with the same tyre tread (tyres approved by BMW) on all 4 wheels


•The difference in tyre tread depth on one axle must not exceed 2 mm (control quality of suspension control systems and wheel alignment requirement)


•The tyres with the higher tread depths must be mounted on the rear axle


•The DOT age difference must not exceed 4 years


•The tyre pressure must be adjusted when the tyres are exchanged


•Wheel exchange between the axles

The wheels may be exchanged between axles to achieve even abrasion. However, BMW does not recommend switching the front wheels to the rear or vice-versa.

The wheel exchange may lead to the following customer complaints:


-
complaints regarding acoustics

-
Risk of increased lane groove sensitivity


Compliance with the following requirements is required when exchanging wheels between the axles:


-
Assess the wear pattern

-
The tread difference between the front and rear wheels must not exceed a maximum of 2-3 mm

-
Exchange the wheels between the axles every 5000 Km





Additionally for all-wheel drive vehicles:


•The tyre size, manufacturer and tyre tread must be identical on all wheels; different tyre sizes between front and rear axles are only permissible if mixed tyres are fitted.


•The tyre tread difference between tyres in all wheel positions must not exceed 2 mm (normal quality of the wheel control systems and wheel alignment requirement)

"

So I'm assuming that's the gospel according to BMW.

[Leem40i]

Originally Posted by avi66

Actually it can be an issue with fitting here i.e. Costco.

"INSTALLATION OF LESS THAN A FULL SET OF TYRES

When a member does not replace tyres in full sets, Costco's tyre fitting policy is to position the new tyres on the rear of a vehicle. This policy is consistent with the direction given from all the major tyre manufacturers and tyre industry associations. Safe vehicle operation is the driving force behind this policy. A few vehicle manufacturers have wording in their owner's manual stating that new tyres should be fitted to the front of a vehicle. Mechanical issues are the driving force through this direction. This direction conflicts with the Industry & Costco’s safety policy of when only 2 tyres are replaced, that the new tyres must be fitted to the rear of the vehicle. The conflict here is safety versus mechanical. When replacing 2 new tyres only on the front of a vehicle, this makes the vehicle unstable and susceptible to sudden lack of stability and over steer. This creates a safety hazard not only for the passengers and driver in the vehicle but it also creates a safety hazard for others who may be harmed by an overturned or fish-tailing vehicle. A members request to sign a waiver of liability for the installation of replacement tyres only on the front axle will be denied by Costco."

That little blurb from Costco is not taking a consideration that many vehicles now have staggered setups. What they're talking about is if you have rear tires that are completely worn out. It's mainly directed towards people that can barely afford the two tires. Unless you ride your tires down to the belts you will never have an issue. What what you posted was just Costco's way of covering their ass for the people that will ride on bald tires

[Leem40i]

Originally Posted by lfdal54

Pulled this from ISTA

"General:


•The tyre size, manufacturer and tyre tread must be the same on one axle


•To meet the BMW standards, the vehicle should be equipped with tyres from the same manufacturer and with the same tyre tread (tyres approved by BMW) on all 4 wheels


•The difference in tyre tread depth on one axle must not exceed 2 mm (control quality of suspension control systems and wheel alignment requirement)


•The tyres with the higher tread depths must be mounted on the rear axle


•The DOT age difference must not exceed 4 years


•The tyre pressure must be adjusted when the tyres are exchanged


•Wheel exchange between the axles

The wheels may be exchanged between axles to achieve even abrasion. However, BMW does not recommend switching the front wheels to the rear or vice-versa.

The wheel exchange may lead to the following customer complaints:


-
complaints regarding acoustics

-
Risk of increased lane groove sensitivity


Compliance with the following requirements is required when exchanging wheels between the axles:


-
Assess the wear pattern

-
The tread difference between the front and rear wheels must not exceed a maximum of 2-3 mm

-
Exchange the wheels between the axles every 5000 Km





Additionally for all-wheel drive vehicles:


•The tyre size, manufacturer and tyre tread must be identical on all wheels; different tyre sizes between front and rear axles are only permissible if mixed tyres are fitted.


•The tyre tread difference between tyres in all wheel positions must not exceed 2 mm (normal quality of the wheel control systems and wheel alignment requirement)

"

So I'm assuming that's the gospel according to BMW.

We have a staggered setup. You don't move tires from the front axle to the rear axle.

[avi66]

Originally Posted by lfdal54

•The tyres with the higher tread depths must be mounted on the rear axle

Basically stating the same as the Costco policy above.

The problem is ISTA is not a public accessible solution (in theory lol). So when you need a new tyre, would a typical tyre supply company be aware of this ?

The wording suggests this is normal practice and common knowledge, like using the same size tyre on the same axel etc.

[lfdal54]

Originally Posted by avi66

Basically stating the same as the Costco policy above.

The problem is ISTA is not a public accessible solution (in theory lol). So when you need a new tyre, would a typical tyre supply company be aware of this ?

The wording suggests this is normal practice and common knowledge, like using the same size tyre on the same axel etc.

I don't disagree. For you folks in the UK, it seems like BMW is more stringent on enforcing requirements than in the US. When I was speaking to Tirerack at least the person I spoke to was very aware of it, but would the local tire shop down the street who barely knows one end of the car from the other? I doubt it.

My built-in caution comes from years of owning Subies. It was a fact of life for them. IIRC, since Subaru is using more electronics in their AWD system they're less picky about tire matching than they used to be. Their AWD system is also not as good as it used to be IMO, but I digress.

As to staggered vs square setups, circumference is circumference.

[Roche]

Originally Posted by Leem40i

Okay so you've gotten advice to replace all four tires because you got a nail in one?. First off unless the front tires were pretty much worn out you don't necessarily have to replace the two fronts. Secondly. Putting new tires in the front and not on the rear is absolutely not an issue. The tolerances for the Xride system is not that tight to wear the simple range in diameter that a tire has as it wears out will make a difference. Anytime you have a staggered setup you are typically going to have to replace one set uf tires before the other.

Yeah - one nail caused this. If it was my old Golf, I'd have just replaced the one tyre on the front for £90 and be done with it! That's what I've paid in the past. But yes - I did both on the tyre fitter's advice.

I really thought this was a simple question lol - hence the title of my post. But it seems that it's definitely not that simple!

[Leem40i]

Originally Posted by lfdal54

As to staggered vs square setups, circumference is circumference.

Incorrect, it's not just the wheels diameter. The offset and wheel size is different and requires the right suspension set up. You can't just mix and match

[Wgosma]

Originally Posted by avi66

If it ain’t in the manual and there’s an issue, it’s BMW fault.

I can find anything on the BMW UK website, in the owners manual, or any documentation produced with my car. So they would have a challenge denying an x drive claim due to tread difference, if they don’t actually provide official readily available info I suspect.

See attached...from the BMW TIS (Technical Information System)

[Mushy007]

Originally Posted by Leem40i

Incorrect, it's not just the wheels diameter. The offset and wheel size is different and requires the right suspension set up. You can't just mix and match

100% agree, the brother in law purchased an X5 and the garage put 21” wheel on over stock BMW 19s, 8 months later the transfer box gave up the ghost, turns out the wheel size and tyre size front to back was way over the specs set by BMW, £4.5k for a new transfer unit and £1k to get the right tyre setup to bring it in tolerance!

[Roche]

Originally Posted by Wgosma

See attached...from the BMW TIS (Technical Information System)

I think the point avi66 is making is that this information isn't easily available to 'the layman'. And, if these small differences can lead to such catastrophic (and expensive) problems, then that info should be very much readily available.

That TIS document is available to BMW technicians or, generally, people in the know.

For the average owner with an X3, there is no mention of these requirements in the owners manual/handbook, or in other easily accessible documents that an owner would have.

[avi66]

Originally Posted by Roche

I think the point avi66 is making is that this information isn't easily available to 'the layman'. And, if these small differences can lead to such catastrophic (and expensive) problems, then that info should be very much readily available.

That TIS document is available to BMW technicians or, generally, people in the know.

For the average owner with an X3, there is no mention of these requirements in the owners manual/handbook, or in other easily accessible documents that an owner would have.

That's exactly my point.

The user manual talks at length about tyre pressure, changing wheels etc, but no mention that a 2mm (which is tiny) tread variance can screw up your Xdrive.

My BMW car manual has a section on tyres, including safety points and warnings, such as "Do not swap between front and rear axles". As far as I can see, there is no mention of 2mm tread variance, even in the section on "Tyre Tread", which warns of a minimum tread depth for summer and winter tyres.

According to the linked TIS pdf, if we needed to replace a single front tyre, and the rear tyres had less tread than a new front, you would need to replace both rear tyres and also the other front if the new tyre was more than 2mm different. It's a shit show and essentially means changing all 4 tyres in a situation when a single tyre replacement triggers the threshold. Given the cost of this and the likelihood of needing to replace tyres, I don't recall reading about this in any G01 reviews this was raised as a cost of ownership issue.

[lfdal54]

Originally Posted by Leem40i

Incorrect, it's not just the wheels diameter. The offset and wheel size is different and requires the right suspension set up. You can't just mix and match

My point is that the circumference matching is all that matters to this particular issue - the number of revs that all the tires make with respect to each other needs to be in a small range to not overstress the components relating to the drive system.

The width, offset, using spacers or not, all affect things other than "pure" rotational driveline issues. Given the number of people that use spacers without a problem its a testament to the robustness of most BMW suspension components. Wheel bearings especially.

[lfdal54]

Originally Posted by avi66

That's exactly my point.

The user manual talks at length about tyre pressure, changing wheels etc, but no mention that a 2mm (which is tiny) tread variance can screw up your Xdrive.

My BMW car manual has a section on tyres, including safety points and warnings, such as "Do not swap between front and rear axles". As far as I can see, there is no mention of 2mm tread variance, even in the section on "Tyre Tread", which warns of a minimum tread depth for summer and winter tyres.

According to the linked TIS pdf, if we needed to replace a single front tyre, and the rear tyres had less tread than a new front, you would need to replace both rear tyres and also the other front if the new tyre was more than 2mm different. It's a shit show and essentially means changing all 4 tyres in a situation when a single tyre replacement triggers the threshold. Given the cost of this and the likelihood of needing to replace tyres, I don't recall reading about this in any G01 reviews this was raised as a cost of ownership issue.

Oddly coming from a Subaru background, especially from back in their 100% mechanical AWD days if I lost one tire after any significant tread wear I'd automatically replace the set. One of the reasons I stuck with a 19" square setup for 3 seasons and winter use. That's expensive enough. With 20's and god forbid 21's a horrendously expensive proposition.

Thing is, do the BMW dealerships even enforce this? Heck, when I've asked the question of the service department they didn't know.

[lfdal54]

Originally Posted by Wgosma

See attached...from the BMW TIS (Technical Information System)

That PDF pretty well matches the excerpt from ISTA I posted above. At least they're being consistent.

[Leem40i]

Originally Posted by lfdal54

My point is that the circumference matching is all that matters to this particular issue - the number of revs that all the tires make with respect to each other needs to be in a small range to not overstress the components relating to the drive system.

The width, offset, using spacers or not, all affect things other than "pure" rotational driveline issues. Given the number of people that use spacers without a problem its a testament to the robustness of most BMW suspension components. Wheel bearings especially.

Agreed

[jrveron]

Originally Posted by avi66

The front/rear tyres are a different ratio on my staggered setup i.e 245/40 v 275/35. Is the sidewall height not 98mm v 96.25mm, so 1.75mm different, before tread ware is even considered. So does that reduce the 2mm tread difference even further as I don’t recall any mention of this.

I don't understand why we can run staggered setups with up to 1% difference between front and rear, but we can't have a tread depth difference of 2mm

I also assume that one axle (potentially the rear) will wear faster than the other, increasing the difference.

Could someone please shed some light here?

[Leem40i]

Originally Posted by jrveron

I don't understand why we can run staggered setups with up to 1% difference between front and rear, but we can't have a tread depth difference of 2mm

I also assume that one axle (potentially the rear) will wear faster than the other, increasing the difference.

Could someone please shed some light here?

All good points. This isn't thr first staggered set up in a vehicle and I've never seen an issue with new tires on one axle. I've always had to replace there's tires first but that was always on a RWD vehicle.

[Keefy]

How the hell are we supposed to get even tyre wear between front and rear axels (or within 2-3mm) with a performance car that has AWD but with rear wheel drive bias ?

And how is the xdrive system so bloody reliant on specific parameters for it to remain reliable? I mean, it’s an AWD vehicle that’s supposedly designed to go on-road or off-road (within reason) and still perform. If the system is so “unique/sensitive or specifically tuned” then it would fail if the car drove over grass, snow, sand etc basically any terrain that it wasn’t designed and tested on when it was being developed?

This really sounds like BMW hitting us with every excuse under the sun for any sort of xdrive failure.

[lfdal54]

Originally Posted by Keefy

......

This really sounds like BMW hitting us with every excuse under the sun for any sort of xdrive failure.

Bingo. The system is probably more than robust enough to stand a tolerance wider than they publish or we'd hear a lot more about transfer case problems.

OTOH, it gives them an out if they either don't want to honor a warranty claim or want to defend an out-of-warranty charge for driveline work.

[avi66]

Originally Posted by Keefy

How the hell are we supposed to get even tyre wear between front and rear axels (or within 2-3mm) with a performance car that has AWD but with rear wheel drive bias ?

And how is the xdrive system so bloody reliant on specific parameters for it to remain reliable? I mean, it’s an AWD vehicle that’s supposedly designed to go on-road or off-road (within reason) and still perform. If the system is so “unique/sensitive or specifically tuned” then it would fail if the car drove over grass, snow, sand etc basically any terrain that it wasn’t designed and tested on when it was being developed?

This really sounds like BMW hitting us with every excuse under the sun for any sort of xdrive failure.

It’s probably to help shift those BMW * rated tyres lol 😂