Do I need to change all four tyres at the same time on a BMW xDrive model?

We have a BMW 18d. The dealer says although it is an X drive, in normal driving 100% of the power is sent to the front and the rear is only used when extra traction is required. The two front tyres are around 2.5 - 3mm but the rear ones are like new. I've learnt that the transfer case doesn't like tolerance differences of more than say 2-3mm - although I cannot find anything written down from BMW. It looks like I need to replace all four tyres in order to keep the transfer case happy. Would you agree?

I also understand I can switch from runflats to non-runflats providing I keep the same tyre dimensions. Is this correct?

Asked on 4 May 2023 by Paul R

Answered by David Ross
Unfortunately many four-wheel-drive vehicles are sensitive to tyre wear imbalance, but this is something vehicle manufacturers are somewhat coy about explaining to their customers.

Our understanding of the tolerance is that the difference in tread depth should be no more than 2mm across an axle, and 3mm between the front and rear axles to avoid any issues. Regular tyre rotation front to rear should mean you can get more life out of each set of tyres, as we would expect the front tyres to wear more heavily on your X1. Regardless, it is an additional expense that a two-wheel-drive BMW owner would not have to worry about, but it is worth doing so to avoid the even greater cost of a replacement transfer case.

You can switch to non-runflats which would help the ride quality as well as bring the cost of new tyres down.
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