We ride on gravel and rocky roads frequently out here in the country. Our tires are 700x28's and 700x25's, all with kevlar type flat belts, and they have no problem at all on very sharp rough stony gravel. Actually, I sort of get a kick out of picking my way through the scary lunar landscape for a mile or two between paved roads to avoid the worst stone 'daggers' that stick up...adds variety. Haven't had a flat from it yet...I've only had flats due to unseen glass shards on smooth paved roads.