Scarab's wheels must meet a number of requirements related to the vehicle and terrain. Firstly, Scarab is a skid-steer vehicle. This means that Scarab turns by driving one side forward and the other side backward, like a tank. This motion imparts great lateral stresses on the wheels.
Also Scarab drives in fine, loose material and across steep slopes. The wheels must find some traction in this difficult terrain and resist slipping downhill.
Finally, Scarab is a lunar prototype so the wheels should be able operate on the moon. The final set of wheels will be able to handle extreme temperatures in a low gravity environment.
Three different wheels have been tested on the rover; one set of commercial skid-loader tires and two sets of experimental lunar wheels. A skid loader is a small construction vehicle that turns like Scarab. Lunar wheels (also known as Tweels) are an experimental wheel design developed by Michelin. Scarab has helped quantify wheel performance in lab and field tests.