My 520 is still in the post but I have been advised to change the tires as soon as it arrives. I thought I'd go down the Lafferty/Watts route with Michelin M12 front and S12 rear but I've got confused with Michelins ridiculous sizing policy whereby a 140/80 is actually a 120/90-18 in everyone else's language. The standard tires on the 520 are Bridgestone Gritty Enduro's in a 140/80-18 size. Is this the same imaginary Michelin size and what size is the Gritty in real money 120/90-18 ? My dealer recommends a Kenda Trackmaster in a 110/100-18 size-highway legal in the States apparently. Is there a budding tire expert out there ?