Rear wheel covers have been extensively tested and are proven elements. A variety of materials can be used. The front wheel options have been studied too and the need to minimize wind input into the steering has been a major issue. Three spoke wheels and partial fairing of the 24 spoke rim seem the most common approaches. A partial fender over the front of the tire has been used. A fairing behind the front wheel and attached to the fork gives a measure of stability. In most cases the clearance between the foot and the front wheel is too close to use this. The time trial and triathlon riders have refined these techniques.