Search Unity

  1. Unity 6 Preview is now available. To find out what's new, have a look at our Unity 6 Preview blog post.
    Dismiss Notice
  2. Unity is excited to announce that we will be collaborating with TheXPlace for a summer game jam from June 13 - June 19. Learn more.
    Dismiss Notice

Question Why are large amounts of torque (5000nm+) required to move a vehicle that weighs 1 ton?

Discussion in 'Physics' started by DBS971, Nov 22, 2022.

  1. DBS971


    Nov 19, 2022
    Hi all, I have decided to pick up some game development skills and have been researching and learning about wheel colliders.

    I've built a test car in a scene and have the heirarchy of objects set up as such:

    On the "car" root object, I have my car control script, Rigidbody and Collider:

    You'll notice that I have the torque (which from what I've read, is in Nm) set to 6000. This is because anything less means that the car creeps along very slowly.

    Currently my script is very basic in terms of applying power to the wheel colliders - that is, I simply am multiplying my Vertical input by the Torque value, divided by the number of drive wheels, as seen below in the highlighted section (slip modifications are to sideways slip only).

    Physics-wise, the car behaves quite nicely for the most part. It has a belivable amount of oversteer when turning under acceleration, and can hold a drift just like a real car (not aiming for simulation physics here, just something that feels "fun").

    Sadly, the issues start when the car starts reaching max speed. It doesn't like driving in a straight line, and my theory so far is that so much torque is being applied, the tyres continue to slip even when driving at speed (as you'd expect with 6000nm going to the rear wheels).

    So, to sum this all up, my question is:

    Why do I need 6000nm of torque just to move the car at a "fun" rate? Going down to around 600nm makes it snail-like... and 600nm of rear wheel torque in real life will completely destroy tyres.

    Things I've checked:

    1. Car mesh is to scale for the physics engine - compared against the default Unity 3d cube, the car is approximately 3 cubes long by 1.5 cubes wide. Not entirely accurate to a real car but close enough that the sizing of the car should be fine (to my limited knowledge).

    2. Car's rigidbody Mass is 1500kgs, so 1.5ton.

    3. Wheel Collider slip values have been adjusted, but I tested resetting them back to the default values and the issue still occurs. Wheel mass has been adjusted to 20kg and the radius is reasonable.

    4. There are no collisions going on with the car's square hitbox.

    5. All Transforms have a scale of 1, 1, 1.

    6. No other calculations going on or physical forces being applied to the car to cause it to struggle to move.


    Any suggestions are most welcome, and I am happy to provide the project if needed to diagnose further.

    Thanks all!

    Attached Files: