My bike has 50mm wide rims and 2.125" Felt "Circuit" tires. The tires on these rims come in at 63mm at the widest point, which is almost 2.5 inches. I don't know if that's just standard tire sizing variance, or due to the rims. They seem heavy and slow to me, so I'm looking for something fat and fast, but I think most manufactures post sizes based on narrower rims. I have ~1.5cm clearance between these tires and fenders at all points. What size range do you think I should be looking at? Any chance I could fit a tire labeled at 2.5", or would that likely be too big? I'd like to go as big as possible.