Wrong.
With the XBCD XP community drivers you can have separate brake/gas axes for the triggers. It also makes deadzones possible which is awesome. You have to use the XBCD drivers specially tailored for the 360 controller, as the originals were meant for use with the original XBOX controllers.
Also, you will have the actually delete the original MS driver files from the system32\drivers folder before the XBCD driver will be recognized. (basically, unplug the controller, delete the MS driver (you can see what filename to delete by going into the device manager), install the XBCD driver, THEN plug the controller back in. If you do not do this exactly, the computer will never use the driver you want for the controller)
Get a wheel when you can though. I used a 360 controller, and while fun, it just doesn't cut it for extended, competitive (did *I* just say that?!) driving since you actually have to concentrate not to overcook steering inputs (unlike wheels, mice, or joysticks).