I was getting quotes for new rear tyres for for my 18"x8" factory rims. I currently have 245/40/18 all round. I was looking to get 255 on the rear but was told that anything wider than 245 with a profile of 40 or more eg. 255/40/18 or 255/45/18 would be illegal as you cannot increase the rolling diameter past the max recommended width of the rim (245 for 18"x8"). I'm not sure what the max recommended width for a 17"x8" rim but I'm assuming it's probably the same ie. 245. If so, then a 265 will not be legal on a 8" rim anyway, even if a 265/35/17 has a rolling diameter less than a 245/40/17 (going less is legal but not the other way around).