2008 X6 4x4 DSC ABS EBV failure

[cbx99]

Hey all,

I've got a 2008 X6 35D with 90k on the clock. I hit the errors mentioned when rapidly accelerating from standstill, almost without fail the errors will pop up on my screen. Once the car is moving past 25 mph, then I can floor it and I wont get the errors, its only when accelerating from standstill and rapidly. If I accelerate gently, then I have no issues and the car drives fine.

Quick searching shows speed sensor issues and changing Transfer Case oil but is there anything else it could be? I've already changed the transfer case servo motor, that didn't resolve the issue. On another note, my Auto Hold throws an error and doesn't work. Could the DSC module be causing this issue? I have staggered tyres, 315/35/20 rear and 245/40/20 front if that helps.

Any ideas on what the issue could be before I take it in to an indy?

[Alan Gunn]

What fault codes come up on a code scan.

[Greydog]

Tyres may be correct size, but are they * rated, are they the same make front and rear. These cars don't like even a small mismatch in tyre circumference front to rear or across axles. If the tyres are not * rated make a small chalk mark at the bottom of each tyre roll the car forward a few wheel revolutions until one chalk mark is at the bottom goes without saying all the others should be in the same position, or close very close.
A friends wife has a 2023 X3 M 40i while they were away from home they needed a new tyre ( OEM were Bridgestone the replacement Pirelli) due to pothole damage within days she was getting similar symptoms you are seeing. They are now in a fight with the Council over the cost of tyres as the fix needed two Bridgestone front tyres so they matched

[Leslie]

245 fronts are not correct is that a typo ? it should be 275/40/20, Oh and welcome

[cbx99]

Tyres may be correct size, but are they * rated, are they the same make front and rear. These cars don't like even a small mismatch in tyre circumference front to rear or across axles. If the tyres are not * rated make a small chalk mark at the bottom of each tyre roll the car forward a few wheel revolutions until one chalk mark is at the bottom goes without saying all the others should be in the same position, or close very close.
A friends wife has a 2023 X3 M 40i while they were away from home they needed a new tyre ( OEM were Bridgestone the replacement Pirelli) due to pothole damage within days she was getting similar symptoms you are seeing. They are now in a fight with the Council over the cost of tyres as the fix needed two Bridgestone front tyres so they matched

OK that's a bit worrying, I'll have to change both rear tyres to compensate for that. I swapped them out for non run flats quite a while back. I'll do the chalk test in the meantime and see what happens. Would simply changing the tyres resolve this issue or is there another workaround?

[cbx99]

245 fronts are not correct is that a typo ? it should be 275/40/20, Oh and welcome

Yes you're correct, they are 275 not 245. Thanks

[Alan Gunn]

Is there a lot of tread difference front to back.
Any more than 2mm i think it is will give problems.
As said do the chalk test before it does any more damage.

[cbx99]

I stuck some masking tape on all the wheels in the 6 o'clock position. Drove it for a few yards and then checked them. The front 2 were almost perfectly aligned, the rear two were out though. The offside rear was around the 6.30 mark and nearside was more towards the 5.30 mark. The offside is worn and needs replacing so I'll replace both of them together. Both the front tyres have around 4mm tread left at the moment.

[Alan Gunn]

What where then markings like front to rear.
Where the fronts at 6 and rears as pictured.
I think that is what you are saying but just checking.

[cbx99]

Yes, the fronts were dead on 6, the rears as pictured

[X5Sport]

The maximum tread depth difference between any tyre and any other tyre is 2mm. Any more than that risks damage to the transfer box or a shattered diff. xDrive cars are very sensitive to tyre types and in my experience the loss of just one tyre usually means a full set change is required if the tyre wear means a jump in tread depth. The problem is the transmission ‘winds up’ due to the different tyre circumferences until something breaks. On a really smooth surface you can feel the car lurching slightly as the stress builds and releases.

I had a sidewall failure on the X6 with the tyres about half-worn and had no option but to replace the full set in order to stay within limits. Changing one axle set isn’t enough, it needed the full set.

BMW aren’t the only ones with this challenge. It’s an issue in Porsche, Jaguar, Mercedes and a few others. Hence each of them having their own ‘approved’ tyre code. On BMW you can fit MOE (Mercedes Original Extended) as well as BMW Approved (with a ) on the sidewall. The outer diameters are matched so no wind up exists. Staggered setups are the ones to take the most care with. We’ve seen a fair few on here ever since the E53 X5 came out. Only the very latest ‘G’ series cars seem to have less of an issue as they have a different transfer box design..

It doesn’t matter about whether you fit ROF (Run-on-Flat) or non-ROF, both have the same issue. Approved tyres are the safest (but expensive) option.

[Leslie]

If the abs/dsc light is on ? id be looking at the reluctor rings on the driveshafts at this age they can crack and split with rust , yes tyres can be an issue if the thread depths vary a lot but I'm not sure its your actual issue at the minute. Have all the tyres the correct pressure as a rear may be compressing under hard acceleration if soft ?

[cbx99]

Yes all the tyre pressures are correct. I'll get rings checked out too just to be safe.