Hiya....Well the bikes are similar and share many components, but the R was really born as an off road machine whereas the X is an adapted version and is really a street bike. The smaller wheels on the X mean that you can fit a wide range of road tyres (I fitted Pirelli Diablos to mine) and you have road bike type handling.

But hey if you love the looks of the R then go with that and ask the guys on here which are the best road tyres to fit. Have fun ciao!!!

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(Now sold on, sob) 2011 Blue XT660X with gold wheels, was 26,500 km.
Engine mods: K&N Stage 1 filter, DNA Stage 2 filter, snorkel removed, Kev fuel mod fitted.
Plus: smoked Puig screen, Yam aluminium sump guard, Yamaha / Acerbis handguards, Givi Trekker aluminium side cases, Leo Vince X3 cans plus Kev front fork mod and Fender Xtender. Just fitted Michelin Road Pilot 3 tyres.

SOLD the XTX for a Super Ten 1200. And just bought a Raptor 700 so staying on here for some tips....