I just purchased a set of sport spike spiders for the rear of my X5 . I have 20x9.5 with 275/40 R20s in the front and 20x10 with 315/35 R20's in the rear. I have the spike spiders hubs installed in the rear (per BMW manual). After the hub is installed , it only take about 30 seconds to install the spikes on each wheel when needed. Total Cost is $400 , shipping is free untill the end of December.

I got a set for my 04 Saab 95 two years ago for traveling from Cal to Oregon ever other month.

X5 is taking over the traveling this year , so I will have to see just how they perform.