Yes, of course!
You can enter any race for free.
When you enter a race, you receive credits (our virtual currency). You can also earn credits randomly as you play races, by clicking barrels (our reward system). You can accumulate these credits as time passes and as you progress in the game.
If you want, you can also purchase additional credits and add them to your balance!
Please note: No credits are needed to play the classic challenges, but you will need them to enter private games or play the "Relax" challenges, which involve credit bidding.