XSeries-forum

[quote="mikem"]
J, I'm disapointed. You could e at least put a picture of the RS4 up and said buy one of these instead.
[/quote]

Surely the lotus would be more appropriate so you could back me up!

Lotus went back in June J. 

GT3 is the way forward

[quote="mikem"]
Lotus went back in June J. 

GT3 is the way forward
[/quote]

Where did I miss that!

Yes it defo is, if I could justify it I would have one too now

Sell the Aldi and you probably could...... >:D

[quote="X5Sport"]
Sell the Aldi and you probably could...... >:D
[/quote]

I need the Audi.

Not sure I could justify a £70k car just sat there for most of the year like the lotus does

[quote="Nat"]
Hi,

I don't think the tyres had anything to do with it. What is sometimes suggested is axle wind. Imagine your back axle, with one 17 inch tyre on one side and one 20 inch tyre on the other. As you drive along the side with the 17 inch wheel will have to go round more times than the other side because of its smaller rolling diameter. That causes the axle to wind itself up. Usually you feel the axle " hop " , normally on very tight slow turns ( like when doing a 3 point turn ) . Thats the axle un-winding itself. In extreme cases like the extreme example I just gaave you ( 17 inch ag 20 inch wheels ) the axle will wind itself to the point of failure if it is a LSD. Normal axles dont suffer from axle wind as just going round corners the outer wheel has to travel further than the inside wheel and thats normal. Now some cars are very sensitive to axle wind. I know a friend who had an issue with a tuareg. Having a bald tyre on one side and a brand new one on the other side gives you a difference of 7-8mm rolling diameter. On some cars that can be enough to cause axle wind, but I have never heard of it on  Bmw's. My Jeep Grand Cherokee was very prone to it, but on tight turns it regularly un-wound itself and was never a problem.
I cant see that having 2 new tyres fitted accross the same axle has in any way caused your issue , unless of course they jacked your car up on the drive shaft or something stupid like that.

Regards,

Nat.
[/quote]

never heard of that problem before - thought that was the plain vanilla job of the diff.

i've had hiluxes, land cruisers before which had diff locks. i've heard the diffs grinding teeth if i locked the diffs and took a tight turn on tarmac, never otherwise.. the diff does its job.

[quote="535dboy"]
[quote="mikem"]
Lotus went back in June J. 

GT3 is the way forward
[/quote]

Where did I miss that!

Yes it defo is, if I could justify it I would have one too now
[/quote]

New cars are "last season" mate. Buy something older for 40 that's gaining money, not loosing it.

Hi,

I am not an engineer so cannot tell you why when there is a rolling difference between front and back of 60 mm it destroys your diff, if that was the cause.

I can only conclude that we shouldnt mix brands of tyres accross axles as well .................however

A good point was made with regards to the spare being used.There is NO limit on how far you can drive with the spare so that in itself blows axle wind out of the water as the issue for me.
Also, if I take my car , the rear tyres  are 315/35/20 and the fronts are 275/40/20..........now both diameters are 20 inch , so they are the same , but the height of the tyre is a % of the width  ...so for the rears its 35% of 315 which is 110.25 and for the fronts its 40% of 275 which is 110.00..........so they are not the same rolling diameter from the factory so the diff MUST compensate in some way. I accept its close, but over many miles it would still cause a problem if it was really the case. You did 100 miles and yours blew up. There are diffs out there with well over 100 K on them.

I regret I cant answer the question , but those are my thoughts. Please do let us know what BMW say .

Regards,

Nat.

Your point is quite correct about front to rear radius being different on the standard 20" tyre sizes however it is minimal and within tolerance the system can cope with.....

BMW warranty is standing up to be counted thankfully but there was no explanation as to the cause,,,I might add prior to the car being recovered I replaced the 20s with a set of matching 17s to eliminate the possible situation of,,,we ain't paying out you got miss matched tyres on the car,,,, 

Good call on the 17's

Can anyone confirm that the x-drive system fitted consists of limited slip diff's?

Wouldn't you need to drive in a perfectly consistent line without changing direction at all for many miles and without changing gear in that time for any significant amount of axel wind to occur?
Also, as the whole system is RWD biased with very little torque going to the front, the front / rear disparity would make even less of a difference wouldn't it?

Just some thoughts be they right or wrong....


Sent from my iPad using Tapatalk

The XDrive unit certainly has a variable clutch system to transfer the torque from front to back and vice versa.

I read a comment a while back that 'suggested' the rolling radius of the Diamaris with the '*' had been tweaked and that was why it had a special mark on the BMW Version only.  I can't find it to check it, but TBH the variation in normal wear is going to result in a much wider range of radii and we would probably all have suffered some form of diff failure.

The only 'limited slip' diff type I know of for certain is the electronic one on the E71 models and E70 X5M model which all have a clever ZF/GKN Driveline torque transfer control on the back with multiple clutches.

Richard

[quote="jaynana"]
never heard of that problem before - thought that was the plain vanilla job of the diff.

i've had hiluxes, land cruisers before which had diff locks. i've heard the diffs grinding teeth if i locked the diffs and took a tight turn on tarmac, never otherwise.. the diff does its job.
[/quote]

+1

Axle Wind only really a major issue on locked diffs, and then you would most likely see it on the centre diff
From research deemed unlikely side to side across an axle unless diff is already knacked....

http://www.oncourse4wd.com/4wd/4wd_axle_windup.asp

can i just say on my old x5 i got 2 brand new tyres on the rear (22s) and i got 285/35/22, on the front it had 2 265/35/22 that were nearly bald and it caused havoc, every time you put your foot down it lit up all the traction asc lights and cut the power, new owner changed all four tyres and it was cured, he also put 265/35/22 on the rear as it had before.

on a seperate not my x5 before that a 2001, just before selling it put a new 19" tyre on the front with a bald one and going round the sharp bend onto our drive it wound its self but just made a horrible sound and scratted at that tyre, where as when our shogun wound its self in the same place i had to jack it up to release the pressure on that wheel.

just something to think about

[quote="shadrack"]
on a seperate not my x5 before that a 2001, just before selling it put a new 19" tyre on the front with a bald one and going round the sharp bend onto our drive it wound its self but just made a horrible sound and scratted at that tyre, where as when our shogun wound its self in the same place i had to jack it up to release the pressure on that wheel.
[/quote]

getting even more interesting..

axle wind up is defined as '.. when you select 4wd and start to corner. The reason is that when 4wd is engaged, you are driving front and rear axles at the same speed all the time - when you corner the front and rear must be driven at different speeds as they take a different track. This causes tension built up within the whole of the drive train and if then, tension is not released it keeps on building up'

are you talking about the same thing?

because an X5 by no means should have a locked diff in normal driving conditions although a 4WD. Shogun could have a locked diff  if you engage 4WD. but not in its normal driving mode.

So much opinion and discussion on this issue,,,the Master Mtech I am friendly with is utterly convinced tyres caused this failure.....in fact when I explained the symptoms to him his immediate response was what's tyre sizes and condition..??