Its really not in "most" cases. If you are going from a 10-15lb tire to a 30-35lb. + tire then the clutch will feel the weight. Just move a few grams around & see how it performs. I wish I still had my #'s from when i went from stock 26's to 27" Executioners (measuring 26"). The weight diff was huge, however like G-Holiday said, no big deal if the weight is close. Unless your really pickyI don't think the weight difference is that big of a deal if they are the same size as stock. It's more when you start going taller with tires.