i have a vulcan 800a, just replaced tyres to day with avon viper!! but i went up to a 160 rear which is probably the largest you can go with out touching the mud guard , i must say seems to turn quicker and lean a little more but the tyre looks better in there than the original 140 "skinny thing" ill let you all no how it wears ! also up a cog on drive sprocket and it does feel a little longer legged now !!!