How do I know the difference between needing a tire, and motor mounts gone bad?

Question

I have a lot of shaking and one Mechanic said motor mounts another said its my tire and rim.

Answer 1

Open the hood, then have a friend start the car and put it in drive, then with the brakes fully applied, press on the gas pedal some and watch and see if the engine raises up. Do the same thing again only this time in reverse. If you have a broken motor mount then the engine will raise up.
If the engine stays in about the same spot, then it could be your tire or rims. The engine will move a little because of the torque applied on the engine.

good luck.

Answer 2

If it shakes while the vehicle is not moving, then you need mounts. If the amount of shaking is relative to your speed (as in, it shakes more the faster you go instead of the faster your engine spins) then its your tires. Sit still, keep it in park, and rev the engine and see if there is excessive shaking.