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Discussion Starter #1
Hi Guys,
Apologies if this is already discussed on the forum, I have recently had my tire punctured so end up replacing rear tires. Since then I noticed car juddering and holding back when accelerating. So I took it to BMW and the Mechanic said that your front tires are of not the same tread therefore Transfer box thinks car is slipping. So he said i should get the front tires changed. So I ended up spending more money to change the front tires.
But the problem remained, I took it back to BMW and they said that it's transfer box that has failed but they will not do the job under the extended warranty as the wheels fitted on the car is not of the right specs. So I want an advise if the response of BMW can be challenged or not ? How did they establish incorrect wheel specs caused transfer box failure and are they suggesting 21" wheels cannot be used on X5 (seemed bit odd)

See below response:

The electronic transfer box located on the back on the main transmission, electronically transfers torque to the required final drive when required. It takes its information from the road speed generated by the wheels through sensors located in the hub assembly, thus transferring required torque to the roadwheels.

The factory specification of your vehicle is fitted with 19” wheels, upon inspection we found 21” wheels fitted to your vehicle. Upon checking the part number we can confirm these wheels are fitted to the E70/71 range, these wheels are in the incorrect specification for your vehicle.

The roadspeed generated by this size wheel will give false information to the transfer box electronics unabling the component to function in the correct manner. In some cases this can cause damage internally to the transfer box/clutch assembly and will result in a replacement required of the transfer box.
 

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The wheel (rim) size doesn't matter. What matters is the diameter of the tyre. So what sizes were those tyres?
 

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Discussion Starter #3
That's what I have on car at the moment.

Rear - 325/30 R21 108Y XL
Front - 295/35R21 108Y XL

Car I have is 2014 X5 30d xdrive F15
 

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With those tyres the difference of circumference between front and back is 1,3 %. I'm sorry to say that the dealer has a valid point because those sizes (fronts) are not the ones with this vehicle specs. On 21" the sizes should be front 285/35R21 and rear 325/30R21.
 

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Discussion Starter #5
Thanks for the info. Now a very silly question, I can simply change the front tyres on the same alloys right?
 

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295 for the front Or alloys measured differently?
I was talking about the width of the alloys. It should be marked at the back of the wheel. But like said shouldn't be a problem installing correct 285/35R21 tyres on those same wheels.
 
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