Iv just fitted a 180/55/17 rear tyre on my ninja 300 and it fits just fine with no rubbing against anything. It looks like I could have gone with a 190 but that's insane.. Lol. Icouldn't find and proper threads with clearance pics, etc. So I took a chance. Went to a reputable racing shop who advised me that it will fit just fine. I rind the ride abit softer that the original tyres with great grip though.