This doesn't have much bearing on the game as a whole, but some competitions are limited to one or the other only - for instance the Trial Mountain endurance race, Polyphony Digital Cup (both Road only) and GT Formula Championship (Race only). Yet again, mk's to the rescue!
Opening up your garage in mk's, you'll see the third row is "Car Type" - this contains the relevant information. You need to hit the F8 key to turn this all into gibberish. Or Hexadecimal as certain members of the populous likt to refer to it.
You'll notice that Road cars are listed as "00000000 00000000", Race cars as "00000001 00000000" and Dirt cars as "00000002 00000000". All you need to do is go in to that box, change the number to the relevant one and you're done. I find it helps to hit the "Enter" key when you're done editing and move to a different box. The press "F8" three more times to cycle through a series of bizarre codes and back to "Road", "Race" or "Dirt" - just to check it's worked.
However, actually getting a non-rally car to rally is a little more complex than that...
Go back to Power.
Go on to Off-Roading.
Last update on 29th April 2003.