It makes no difference how many frames you use for a 360 turn, so long as you get the forward movement of the vehicle right so that the tires don't look like they slip. Once you set your keyframes for the tire and the forward position of the vehicle for one full tire rotation, you can move that keyframe to adjust the speed. After that it's only a matter of copy-paste keys and adding an extra 360 degrees for the rotation and increasing the directional distance for the forward movement the same amount as it took for the first tire rotation.

In Maya, you could write a simple MEL script for this sort of thing, and then all you'd have to do is move the car around.

Hope this helps.