Tires referred to as 24” can be one of several sizes. Juvenile mountain bikes and Schwinn Cruisers (S-2) have a bead seat diameter of 507 millimeters. Some juvenile roadsters, time trial, triathlon, small road and Terry bicycles take a bead seat diameter of 520 millimeters. Other juvenile roadsters, small road, Raleigh bikes and wheel chairs need a bead seat of 540 millimeters. Make sure you know which size you need. If you get a tire with the wrong bead seat diameter it just won’t fit on your rim, no matter how hard you try. If you need help determining which tire you need please go to our helpdesk and send us your question.