[amw896]

I wouldn't mess too much outside this range and I think most transfer cases allow for about a 2-3% difference if I remember correctly. I had an is350awd and didnt think much of switching to a staggered setup but it led to big problems. Normal tire wear will keep you within 1% rolling diameter easily. It's when you start messing with different wheel sizes that u need to be careful.

[anthoj]

I know this is somewhat of an old thread but I'd like to share my experience with x-drive and RWD. I switch between two of my cars daily with these tires setup:

2011 E92 335i (RWD)
235/35/19 and 275/30/19

and

2015 F15 X5 (X-drive)
255/50/19 and 255/50/19 (stock)

However harsh or soft I drive, the E92 rear tires always wear out faster. For every front tire set change I do, I need to do two tire changes for the rear.

It's the complete opposite for the F15. Fronts wear out significantly faster. Since it's a newer car I'm just now changing to a different set of wheels and tires, but I would estimate that the fronts wear out more than twice as fast as the rears (comparing to my E92). Since it was a square setup, I kept rotating the tires, which is why they have lasted this long.

I'm now using 255/50/19 and 285/45/19, on the X5, I have yet to see how this changes the tread wear.

[Manivxr]

Originally Posted by Blubaron79

Wrong. Drive an xdrive car. The rears always wear quicker. This is my 3rd BMW with xdrive. These cars are rear drive biased.

+1

[Sigtran]

On my xDrive car and my driving style and conditions, front tyres wear faster, that is a fact. Maybe because of lot of city driving.

Tyres are OEM BMW Bridgestone runflat, front 225/45/R18 rears 255/40/R18.

Always inflated as per BMW specification and did ~30k kilometers with them. Now front are ~2-2.5mm thread depth, but rears are ~4-4.5mm.

Obviously cannot rotate front<->rear, so I am open to suggestions what to do for next summer season? To buy just a new set of front tyres, or should I buy all 4 new (waisting 4.5mm thread) in order to protect xDrive. Or would this difference (~8mm new front and 4.5mm rear) be no issue for xDrive and transfercase?

Q&A: Replacing tyres at 3mm tread “an absolute waste” says Michelin director
https://www.honestjohn.co.uk/news/mi...elin-director/

[awilki0101]

On my 2016 340 xdrive I am going through rear tires twice as fast as front. Went for a tire repair a couple days ago due to a screw and fronts measure 7/32 and rear 3/32. Staggered set up on Michelin PS4s

[Billfitz]

That's probably related to using a staggered set up. One uses a wider rear tire for increased contact area. The wider contact area increases road friction, which gives better grip, but also decreases tread life.

[Sigtran]

Originally Posted by Billfitz

The wider contact area increases road friction, which gives better grip, but also decreases tread life.

Wider contact area gives better grip when pushed hard, but when driving normally, wider area will put less pressure per surface contact area and will increase thread life.

Just imagine that on rear on one side you have 225, and on other 255. On 225 there shall be more pressure per contact area, so tyre wear will be increased comparing to 255... And this is one of the reasons why my front 225 are having more wear then rear 255's. Other being a lot of city driving, friction on turning and frequent stops where much more pressure/weight is on front tyres. All in all, normal...

On more powerful RWD, on square setup and where most of travel is open road and occasionally hard accelerations, it makes sense that rear tyres are the ones to wear faster...

[Billfitz]

On the face of it that seems logical, but the truth of the matter is that the wider the tire the higher the rolling resistance. Higher rolling resistance decreases tire life and increases fuel consumption as well. That's why you see such narrow tires on cars that can't afford to have high rolling resistance, Toyota Prius for example.

[Sigtran]

Originally Posted by Billfitz

On the face of it that seems logical, but the truth of the matter is that the wider the tire the higher the rolling resistance. Higher rolling resistance decreases tire life and increases fuel consumption as well.

Higher total rolling resistance of course yes, but not per mm2 (or square inch). Friction per (contact) area is with wider tyre maybe even lower, since the same total weight pressure is now supported by bigger area, hence with wider tyre lower tyre wear and longer thread life. This is what I experienced. Of course if not burning-out, but doing only normal driving.

We should not be forgetting that front tyres have naturally more wear if lot of city driving (turning and stopping).

I think only if most of milage is on open road and/or relatively often starting hard on accelerator (especially on RWD) I think it is possible that wider rear tyres wear faster then front. Of course, if inflated correctly and same type (softer tyres wear faster).

So I think it seems normal what I experienced, question is what to do? To change just front tyres?

[garanadhav]

Originally Posted by kzflags

its almost a given now that the rule of thumb to follow for xdrive vehicles is to keep the rolling diameters within 1% front and rear. However, from an online manual (which the link is expired lol) it states:

"The tire circumference can fluctuate up to 1% or more as a result of mixed tires or wear. The tire tolerance logic decides depending on the driver's command and driving situation whether the slip is to occur in the transfer case clutch or at the contact area between tire and road.

If the slip is permitted in the transfer case clutch,Onlinesbi sudoku incometaxindiaefiling the locking pressure set by the pre-con- trol is reduced in order to keep the work loss low. In the driving dynamic control situation, the clutch is locked slightly more than normal, the four wheel drive is always guaranteed when required.

For maximum xDrive performance, tires (and wheels) of the same diameter should be installed on the vehicle."

The last part mentions yes, for maximum performance the same diameter should be installed. but how does it account for a set of front tires that are balding and a set of rear tires with close to 100% tread. this will more than likely cause the rolling diameters to be >1% no?

Is there any concrete evidence from a BMW rep or anywhere online that states specifically, the xdrive system will explode and cease to function if the wheels are indeed >1%? Or is this just a myth that has become fact by way of word of mouth? any personal horror stories? any members running wheels clearly >1% diameter on xdrive with no issues

you continuously drive around with the transfer case constantly slipping due to mismatched tires that it will eventually wear the clutches. It's not rocket surgery.

[Billfitz]

XDrive does not have a mechanical transfer case, so what applies to those doesn't apply to xDrive.

[amancuso]

Definitely not a myth. When I bought my X5, it had the wrong size front tires on it, and I didn't know. I drove it that way for 10k miles. I always thought it was a little odd the groaning noise and weird torquing I would feel in the steering wheel it would make over uneven pavements or when traversing a crown in the road. When I was finally convinced something was wrong, I took it to my indy who pointed out the wrong size tires. The tires caused a gear in my front transfer case to wear out causing the odd wheel pulling and groaning sounds. Changed the gear in the case and a set of 4 new tires and the car was silent and smooth again. Don't cheap out on tires or you'll be left holding the bill for a repair.

[keith0333]

Trying to run staggered on my 435xdrive trying to go with this set up. running a 19x8.5 245x35front and 19 x9.5 rear 275 x30. Any suggestions

[tobefair-idontcare]

Originally Posted by keith0333

Trying to run staggered on my 435xdrive trying to go with this set up. running a 19x8.5 245x35front and 19 x9.5 rear 275 x30. Any suggestions

https://tiresize.com/wheel-offset-calculator/

Use this calculator to help you determine rolling diameter and offset. This little thing helped me immensely when I was trying to learn about staggered wheel setups and offsets. You can plug in your current tire specs and the new tire specs you want to run to see how they compare, as well as the new front and rear specs to see if they're within the 1% rolling diameter margins. Just remember that all F series cars, that I'm aware of, are meant to run as close to a 26" rolling diameter as possible. Deviating from this will exaggerate wheel gap, for better or worse, and effect the computers ability to judge it's own speed.

The tire combo you chose looks to be right at 1.2%. Best of luck.

[Assassin]

The "1% Myth" question is often asked.............

I posted the information below on another thread in Dec 2018. It was obtained direct from BMW.

--------------------------------------------------------------------------------------------------

The explicit position from BMW is given here:

Extracts from an email chain between myself and the BMW Genius at the dealership I bought my car from when I asked for precise information on this subject amongst others....

The question I asked:....................

"Hi xxxxx, thanks for your help in this matter, but I'm afraid it doesn't really answer my question.

As I mentioned the BMW forums are alive with transfer box issues and queries relating to tyre fitment. Having just spent over £40k on a new Xdrive I would like the official BMW UK guidance on the key factors to be considered when monitoring tyre wear / fitting new tyres to a model with Xdrive so that I can avoid any premature wear / failure of the component.

The UK owners manual gives no meaningful guidance or dos/ don'ts other that use star rated tyres. For my specific model [2018 F31 335d Xdrive Shadow Edition - staggered 19" 704M wheels] I would like to know if:

1) the make / tread depths on tyres across the same axle must be the same or within a specified tolerance. If so, what is that tolerance?

2) is there [as seems to be case in the US i.e. ~1% ] a specific ratio between the rolling circumference of front / rear tyres that must be maintained to minimise stress on the transfer box? If so, what is that tolerance?

These factors are deemed to be critical by all the guys in the UK/US who have had transfer box problems / failures / replacements. At least BMW USA seem to expressed a view on the acceptable ration between the rolling circumference of front v rear tyres on the xdrives to avoid transfer box problems.

Can you please forward my query to the relevant BMW technical department specialists and get them to provide the relevant information. I am happy to be contacted direct should they prefer that approach to ensure clarity.

Please see the links below which are a small example of the issues posted. There are many more:

Tolerance discussion ~1%

https://f30.bimmerpost.com/forums/se...58921360&pp=30

https://www.bimmerforums.co.uk/forum...rchid=31358615

Regards "
---------------------------------------------------------------------------------

The reply I got back eventually........

"I have had another reply from BMW. This should provide an appropriate answer hopefully.

Regards,

The following information taken direct from AIR states a maximum 2mm between all tyres on an X Drive vehicle.
Its in black and white direct from BMW. Problem solved .
Repair instruction
Notes and specifications for tyre / wheel exchange
3612... | REP-ALG-RAGRP36-3600_REIFENTAUSCH - V.6
ui-button
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)
XXXXXX XXXXXXX

BMW Genius"

There you have it.

[J555]

...and then comes Alpina with 1.9% of factory difference between fronts and rears.

[zibbit]

I'll add my 2 cents..

On staggered factory sizes A/S tires (225/35R20, 255/30R20), my '14 335ix MPE had troubles braking in slushy snow. When you were almost at a stop it seemed like the car was always trying to push you forward. The ONLY way I could stop the car from ramming the car in front of me at EVERY intersection was to pull the e-brake, then the car would stop. No matter how hard you pushed the pedal down, the front tires would lock and the car would continue to creep forward. Despite 3 trips to dealer complaining about this situation and them saying the brakes were in perfect operation I had to correct the situation.

Now, I'm running a 255/35R19 square A/S setup, and for the past two winters I never experienced that situation again. Not to mention, but running a square setup instantly fixed my road tracking issues as well. I'll probably not ever buy another staggered X-Drive again.. Instead I'll insist it has a square setup.

I will say after coming from a Subaru background, I'm still not a fan of the X-drive technology.. but, I've learnt to cope with a couple flaws in the cars design.

[Skyhigh]

My instant thought is that the staggered setup had nothing to do with your bad coming to rest. You are most likely running completely different tires now, which are simply better. Some winter tires are clearly not as good as others. (I am for example extremely dissatisfied with my Micheline X-Ice-s on my Audi...)
That said - driving 255 width in winter (staggered or not) is asking for trouble.

Either way - none of this has anything to do with xDrive. xDrive sets you in motion, not the opposite.

[Billfitz]

A major factor in winter driving is that wider tires aren't better, they're worse. Maximum grip happens when the tires push through snow and slush to make contact with the pavement. Wider tires tend to float on snow and slush, reducing both acceleration and braking capability. Wider tires don't work as well on hard packed snow either. Their tendency to float prevents the tread from digging in as well as with narrower tires.

[Skyhigh]

That's partially true only and only to a certain extent. You will not do better in winter with bycicle width tires, you can be absolutely sure about that

There is a huge dependency on the definition of "winter". Soft snow / hard snow / ice / semi-ice ......!?

Wider tires do get better grip on hard-packed snow AND ice, but only to a certain width, after which it becomes counter-efficient.

The consensus, based on tests and experience, seems to be that, from the typical car tire widths, 215-225 is probably the golden middle. Anything thinner than that - you may experience reduced grip in certain situations (typically ice), anything larger - you are slowly a sled-club candidate. Obviously there are a number of other factors too, like weight of the vehicle.

I drive 225 width on both my cars in the winter. Cannot complain (except from the rediculous Michelin X-Ice-s ... who could know X-ice apparently means "not for ice")

[BBri89]

Bear in mind the quality of the tyre might be more important than the width.

Good quality premium brand in a narrower or wider tyre is likely to be better than a cheaper less reputable brand in the "ideal" width.


Tyres, perhaps more so than anything, you get what you pay for.
Since they're the only thing between the car and the road it is worth going with the best you can afford.

[Skyhigh]

Michelin X-ice being a good example that there are exceptions to the above they were one of the most (if not THE most) expensive I could choose between.