X-Drive trye depth variation
Discussion
Annoyingly got my first puncture in 6 years yesterday, it appears something has pierced the sidewall of the O/S/F.
On RFT so pulled over, inflated again and just got it home with 20psi in. Tyre is scrap due to the sidewall location.
Current tread depths are both fronts on 6mm, both rears on 4.5mm.
I'm aware that i'll need to change both on the same axle, so a pair of fronts, but solid information about the rears seems hard to come by.
My thoughts are that 8mm new on the front is too much of a difference with the rears on 4.5mm which could lead to transfer box issues.
Using the usual F31 335d staggered wheels, so 225/40/19 fronts and 255/35/19 rears.
We're away in a weeks time to Brittany in France, so need to get advice and it sorted early next week.
On RFT so pulled over, inflated again and just got it home with 20psi in. Tyre is scrap due to the sidewall location.
Current tread depths are both fronts on 6mm, both rears on 4.5mm.
I'm aware that i'll need to change both on the same axle, so a pair of fronts, but solid information about the rears seems hard to come by.
My thoughts are that 8mm new on the front is too much of a difference with the rears on 4.5mm which could lead to transfer box issues.
Using the usual F31 335d staggered wheels, so 225/40/19 fronts and 255/35/19 rears.
We're away in a weeks time to Brittany in France, so need to get advice and it sorted early next week.
Edited by sortedcossie on Sunday 8th February 13:10
I think you will have issues as the difference between axles tread wise is too great so sadly all 4 will need replacing.
You can try, but might cause yourself more issues viz transfer case.
Check with BMW but I am pretty sure the tread difference between axles will be outside of the max allowed. My experience on my 5 series with xdrive and the transfer case is that my car was incredibly sensitive to tolerances and I ended up sadly buying 4 new run flats to solve my issues!
You can try, but might cause yourself more issues viz transfer case.
Check with BMW but I am pretty sure the tread difference between axles will be outside of the max allowed. My experience on my 5 series with xdrive and the transfer case is that my car was incredibly sensitive to tolerances and I ended up sadly buying 4 new run flats to solve my issues!
It's hard to find 'official' BMW rules on this, but I've read on many BMW forums that it has to be within 1% front to rear (I've also read 2mm front to rear too - but I think that's people mixing up the same axle tolerance)...which allows enough tolerance for the standard tyre sizes to wear at different rates (front to rear of course). Single axle difference should be no more than 2mm.
On my F31 the front is a 225/40r19 and the rear a 255/35r19 - so rear is actually 0.2% smaller as standard. Which means a diameter of 663mm front and 661mm rear.
A 2mm difference on the rear tread depth would reduce the diameter to 657mm (661mm - 2x2mm), which is <1% difference (0.6%).
To put it another way, mine was in for some warranty work and some servicing, and despite pointing out other advisory items - such as wanting to change both front tyres because they were below the dealer's recommended 4mm min tread depth and NOT because the front to rear variance was too much for the XDrive (rears were 6.5mm). Of course the replacement tyre they wanted to sell me was 2x the price they are on the big online tyre sellers.
Also, my car was sold as a BMW AUC with more than 2mm difference front to rear (brand new rears with 6.8mm and fronts at about 4.5mm)...it was the same car that the BMW dealer recommended I replace the fronts which were on 3.9mm / 4.2mm when it went in for servicing.
On my F31 the front is a 225/40r19 and the rear a 255/35r19 - so rear is actually 0.2% smaller as standard. Which means a diameter of 663mm front and 661mm rear.
A 2mm difference on the rear tread depth would reduce the diameter to 657mm (661mm - 2x2mm), which is <1% difference (0.6%).
To put it another way, mine was in for some warranty work and some servicing, and despite pointing out other advisory items - such as wanting to change both front tyres because they were below the dealer's recommended 4mm min tread depth and NOT because the front to rear variance was too much for the XDrive (rears were 6.5mm). Of course the replacement tyre they wanted to sell me was 2x the price they are on the big online tyre sellers.
Also, my car was sold as a BMW AUC with more than 2mm difference front to rear (brand new rears with 6.8mm and fronts at about 4.5mm)...it was the same car that the BMW dealer recommended I replace the fronts which were on 3.9mm / 4.2mm when it went in for servicing.
Edited by mmm-five on Sunday 8th February 13:38
There was a thread on here a few years ago that done this to death.
The overall opinion was that all four needed to be petty close, 10-15% on the rolling dia comes to mind but don't quote me.
One of the reasons I chose an Audi quattro as they are much more forgiving, only the Axel's need to be the same.
The overall opinion was that all four needed to be petty close, 10-15% on the rolling dia comes to mind but don't quote me.
One of the reasons I chose an Audi quattro as they are much more forgiving, only the Axel's need to be the same.
sortedcossie said:
On RFT so pulled over, inflated again and just got it home with 20psi in. Tyre is scrap due to the sidewall location.
If it hasn't been driven flat just get the tyre fixed by a tyre specialist who can do a proper vulcanised repair. The last one I had done cost £30. They'll need the vehicle or wheel for a couple of hours because the process takes time. Recommended.You cannot find open public advice on this. People will quote Technical Service Bulletins, but that is not public advice. I think the issue was big up until LCI F3* series. After that the output Flexi shaft went from solid aluminium to a rubber joint. Much has been written on US sites about this, and it seemed pre-LCI 4 cylinder diesels were worse.
As you should change when you get to 3mm, then the difference is not too massive. I would not change both across axle if the non-punctured tyre was above 4mm (most new tyres nowadays are around 7mm, an 8mm tread depth is vanishingly rare now). With a staggered set, there is always a difference front to rear.
As you should change when you get to 3mm, then the difference is not too massive. I would not change both across axle if the non-punctured tyre was above 4mm (most new tyres nowadays are around 7mm, an 8mm tread depth is vanishingly rare now). With a staggered set, there is always a difference front to rear.
Edited by Pica-Pica on Sunday 8th February 16:13
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