Good thing you pack a flat kit because NO tire is flat proof!! The weight of a heavier tire will prevent you from accelerating from a dead stop to whatever speed, say crusing speed as fast as you could with a lighter tire...BUT we're only talking maybe a second! Also the heavier tire will prevent higher speeds that a racing tire might achieve...but again we're only talking about maybe 5 mph on top speed which won't mean a thing to you if your not racing. And heavier tires might become more of a burden to push during long rides. BUT having said all of that, last years 4 person team winner of the RAAM race rode on Armadillo's! And I rode them on 158 mile one day trips and don't complain about them.