It's pretty much a consensus among racers that Force Feedback Racing Wheels are the best choice for racing games. Make sure your wheel is compatible with DirectX 9 or 10 . You can find this information on your wheel's instruction manual, or by googling it.
Just make sure that whatever wheel you buy has a minimum of 900 degrees rotation angle and an analog/digital control combination of 8 directional + 24 incremental steps . Some people have reported trouble trying MLG wheels due to their lack of driver support, so if you have another wheel that you use without issues, it's probably better to keep using it .