I do about 13,000 miles a year in mine. I swapped to 19" sport tyres for the winter and could hardly notice much difference to the 20's. The X5 is certainly harsher than my X3 which runs on conventional 18's but i reckon it's down to the ROF tyres irrespective of size.

I would certainly buy the 20's again if replacing my E70 with another.

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Fastbuck
2009 F01 7 Series 3.0D SE Saphire Black/ Oyster
2008 E83 X3 2.0D SE Montego Blue/ Black
2007 E70 X5 3.0D SE Space Grey/ Beige - SOLD
2006 Land Rover Freelander Sport TD4 Zambezi Silver/Black - SOLD
2005 W203 C200K Sports Coupe Jasper Blue/Artico Black - SOLD
2004 W211 E320 CDI Avantgarde Brilliant Silver/Alpaca Grey - SOLD
2001 E39 530i SE Crystal Green/ Beige - SOLD