 Experienced users with sufficient upper-body strength can generally balance the chair on its rear wheels, a "wheelie", and the "tippyness" of the chair controls the ease with which this can be initiated.The wheelie allows an independent wheelchair user to climb and descend curbs and move more easily over small obstacles and irregular ground such as cobbles.The rear wheels of self-propelled wheelchairs typically range from 20–24 inches (51–61 cm)in diameter, and commonly resemble bicycle wheels.