INDYCAR
separate specifications for superspeedway and road/street/short ovals
Superspeedway-specific aerodynamic bodywork, featuring rear-wheel guards that have a slightly different shape than the sets being used on the road/street circuits and the oval races at Texas Motor Speedway, Iowa Speedway and the Milwaukee Mile.

Aero kit to be used at the 2.5-mile oval for the Indianapolis 500 and at the 2-mile Auto Club Speedway

The rear wheel guard was designed to reduce wheel-to-wheel contact.
The rear-wheel guard/wings work in combination with the other bodywork to create less drag and more downforce.

Wind tunnel testing of an open-wheeled race car

The model hangs from a strut in the ceiling that also acts as a spring balance. The wheels are actually separate from the model and attached to the walls of the tunnel as vibration from the tyres on the road would corrupt the data.

A1GP
Image of a race car model in a low speed wind tunnel equipped with a moving belt system

2013 Pikes Peak Open Aerodynamic/Wing Clarification
The furthest point of any rear wing or device cannot extend more than 12 inches from the furthest point of the body on the rear of the vehicle. The highest point of any aerodynamic device or wing shall be limited to no more than 18 inches above the tallest point of the cab on the vehicle.

Source: 2013 PPIHC Rulebook - Pikes Peak International Hill Climb

Effect of the height of the front and rear wings on downforce and drag

Wheel force transducers and measuring hubs acquire dynamic forces and torques in the development of vehicles and 
optimization of vehicle dynamics.

Kistler RoaDyn P103/106
For the measurement of braking and acceleration torque on passenger cars and SUV in the 
 areas of traction control ABS systems, coasting moment. Available with slip ring and telemetry 
 transmission. Customized ranges on request.

Exa PowerFLOW aerodynamic simulation of Peugeot Sport's winning 208 T16 Pikes Peak Racecar. PowerFLOW helped Peugeot Sport achieve maximum downforce for the race.

Image: Exa Corporation

Peugeot 208 T16

Exa PowerFLOW simulations exclusive aerodynamic test for Peugeot 208 T16 Pikes Peak Racecar. 

2013 Monster Sport Super 86
Two wings, diffuser

Aerodynamic wings, ground effects, and spoilers

Lexus LFA weight distribution