I recently found out about a cheat unlocks all cars.
Does this code has any downsides on xbox 360?  :|]

Try it all you want but it really won't work. No controller codes for B3.

Generally the worst thing to happen to B3 is that you lose all your cars so you'd be back where you started anyway.

What did you want to try? If it's something messing with modded consoles or memory units then it could be risky.

There are only minor helps to unlocking cars you don't have, like rushing takedown totals by doing road rage (when you reach 150 total you get a Super Assassin, one of the best cars in the game). Or having a series locked race online with the host who has all the series unlocked.

If you want to race online you'll have to unlock the tracks too, so play through the World Tour (it only needs bronze to keep unlocking tracks mostly) ignore the crash events.

Thx 4 but do u no da code is said 2 all da cars.
 

There is no code. Whatever you read or heard was wrong. No code unlocks all the cars/tracks. No code does anything.

Burnout 2 had cheats you could unlock by playing the game, you could turn traffic off or have infinite boost etc. But not B3.