Hey everyone — this is my first post here, so bear with me if I miss any formatting conventions.
If you’re building a vehicle that’s significantly larger than the default scale (e.g., trucks, haulers, etc.), don’t forget to scale your axles appropriately with your wheels. This might sound obvious in hindsight, but it caused me days of debugging.
I ran into an issue where the front wheels of my truck would wobble or spin erratically, especially during steering. I spent hours tweaking mass properties, trying different constraint setups, rewriting scripts — basically reinventing the wheel — and nothing worked.
It turns out that when you scale up the vehicle, if the axle or suspension geometry remains at default (especially when using HingeConstraints or cylindrical attachments), the physics engine can’t properly stabilize the wheel under torque and steering forces. The result is unpredictable rotational behavior, especially at higher speeds or with large mass differentials between wheel and chassis.
After resizing the axles (in proportion to the larger wheels), the instability was completely resolved.
So if anyone runs into the same issue — especially when upscaling vehicles — make sure your axle geometry matches your wheel size. Hopefully, this saves someone else from the same rabbit hole I went down.