Juddering at low speed

[Mickybo]

Hi guys new member and just bought a 2012 X6 40d yesterday and driving it last night noticed on occasion when accelerating and reversing at low speed I'm getting a juddering like clutch judder but is fine in a straight line, have googled and seems everyone gets this problem with the xdrive system and it's either tyres or transfer box, tyres on it are

front  275/40/20 106WXL

rear  315/35/20 110WXL 

the front and rear are different tyres but has the same tyres per axle and all tread levels look similar 

[Greydog]

Morning Micheal

Welcome to the forum, tasty car.

Tyre size looks OK (check the tyre info sticker on the door shut) but the Xdrive system is sensitive to different rolling radius of tyres front to rear, are your tyres fitted Run Flats (they should be I believe)? What your getting is wind up in the transfer case which can cause expensive damage. There is a ton of information on the Web on this subject which appears far worse with the staggered set up.

BMW recommend only Star rated tyres be used to ensure the front/rear rolling radius is as close as possible. My X5 came with Yoko;s fitted when I brought it same symptoms as yours, I parked the car on a level piece of road and made a chalk mark on the tyre front and rear at ground level then got my son to roll the car forward while i watched the rear at 1 revolution chalk mark back to the ground the front had gone way past maybe 30 or 40mm. I fitted 4 Michelin Diamaris which fixed the issues currently running Bridgstones with no problems. Over the years I have run Pirelli, Dunlop and Falken but all 4 have been changed at the same time I always use the same fitting centre and we stand the tyres side by side to see if they are the same diameter before fitting. We did find a difference with the Dunlop's he sent the fronts back the replacements were a match. Bit of a Faff but cheaper than transmission damage.

Dave

[Mickybo]

Hi greydog (dave), not runflats on it, pretty budget tyres, got the car from a local dealer and this is our 3rd car from them as they only specialise in high end quality cars, had a Q7 for 5 months  just before this X6 and the dealer took it back without any hassle as it had ongoing issues, I do know it's the large staggered wheels but a car like this needs them car is pretty much showroom condition. just the car came into them with these tyres on it and still have about 5-6mm on them however did notice yesterday that the rears are m+s marked but the fronts aren't. Wife hasn't noticed any judder and to be fair I dropped the kids to the bus this morning and car was smooth and perfect and I can't see the dealer saying yep no problem I'll fit £700 worth of new tyres for you 😂 so hopefully these tyres will wear out pretty quickly and I can get something descent on as a car like this deserves them. thanks

[Greydog]

Hi Micheal

Fingers crossed for you !! My 4.6 has the same size tyres so I know what you mean, obviously wind up occurs even in a straight line but is really noticeable when on lock parking reversing etc I would do the chalk mark test also every now and then open your door before you switch off if you hear a clicking sound after switch off the transfer case gear is damaged and will need attention.

[Mickybo]

just wondering if anyone can suggest what tyres to go for that are non runflat as I'm taking it back to the dealer and have offered to pay half the price of replacing all 4 tyres but don't want to pay over the odds for the top end budget would be about 600 for the 4 

[Greydog]

Morning Micheal

I would check the discount tyre sites they often have deals going on that would help. Our sons friend runs Nexen on his X5 3.0d same sizes as ours and has had no issues. I think the trick is to (a) stand a rear and front side by side to see how close they are in diameter if there is little difference OK, if there is a difference (my Dunlops were nearly 10mm) but swapped the front pair with the wholesaler and virtually no difference as I said bit of a faff but in my opinion worth it (b) Make sure you get 4 wheel alignment checked and adjusted if needed after fitting to protect your investment.

My current set of Bridgestone were £670 fitted just over a year ago and I am very happy with them., it could be that due to odd tyre wear (tracking) the previous owner changed tyres at different times putting the wear rate (and rolling radius) out of sync.

Good luck

Dave