In the new beta for The Crew the framerate is fixed to 30 frames per second like on console and there is no way you can alter this. On the official Ubisoft Forum a user was complaining about that fact. A community manager first wrote back, that The Crew supports triple screen setups on PC and that Ubisoft just wanted to have the best performance. But later he appeased those complaining by writing, that the final game will have a different option:
"We can officially say that we're aiming for 60FPS on PC at launch. Our Beta build is still more performant at 30FPS, but you can expect to play at 60FPS on PC when the game is launched."
So obviously you get a better performance out of the game with 60 fps, if you have a decent PC setup at home.