Dude, have you tried Google? lol..
Here are some:
Road Rash Cheats
Platform: PC
Road Rash Drive Faster
If you have a Rat Bike, hold the KICK button to drive faster.
Road Rash Overkill Mode
During the game, press "xyzzy" to get access cheats. Then any time you want type in "overkill" and you will have killing mode on.
Road Rash No police
During the game, press "xyzzy" to get access cheats. Then any time you want type in "bribe"
Road Rash Nitros
During the game, press "xyzzy" to get access cheats. Then any time you want type in "spoon!"
Road Rash Be armed with a chain
During the game, press "xyzzy" to get access cheats. Then any time you want type in "thwack!"
Road Rash Be armed with a club
During the game, press "xyzzy" to get access cheats. Then any time you want type in "k'thunk"