Have run 235/40/18 on the rear for many years but stick with 215/40/17 on the front its a great combo. On Topspeed runs I squeeze on 225/40/19 at the back which can only be used in a straight line & they rub on the Bruntingthorpe bend. Fully trimmed arches. Don't go big on the front it will effect the way it handles & steers. Oh yes it has coilovers.