Just to give you an idea how much more the RFTs weigh. *The Michelin
18 inch rft that come on the x5 weigh 13 lbs more per tire over the
non rft Michelin equivalent (source: tirerack.com). 52 lbs of
rotational mass will definitely affect fuel efficiency.

When I went to non rft on my 3er my fuel efficiency went up by ~.5mpg.
I attribute that to the reduction in mass at the corners(total weight loss: ~40lbs).

I myself am keeping the RFT on my x5. *Unfortunately with the 3rd row
there is no room for a spare


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