to modify the disc brakes so they rotate?

Why would you even need that ???

no..?

lol where do people come up with ideas thinking they can mod out the game so everything works the way they want it to?

there is an improvement suggestion area you know

because in real life the discs move. and since it was a pic i just wondered if we can make it rotate. somehow.

id like to use some of these discs that have holes in them but they look stupid stationary while the wheels move.

As said, no you can't modify this.

Quote from XCNuse :

lol where do people come up with ideas thinking they can mod out the game so everything works the way they want it to?

I think that comes from a lack of understanding how the game works internally (no offence). Textures are easy to modify, models can be modified to some extent (not actually in LFS, but generally in 3D games). What can not be modified is actual game logic. 3D models and textures are "hard" data so to say. The game doesn't know the exact content of these and just uses what it gets. Making a model rotate with some other model is game logic, that needs to be programmed.

Of course, even game logic can be modified but only with hacking the code / memory alteration. This makes the game invalid to other clients and is far beyond simple modifying.