and what if they don't is there another way of checking/testing thanks
You would notice a difference if the wheels are swopped over. And with regards to the discs, you'd only feel the vibration when braking. In my 15 years being in the trade, I've never known discs to cause vibration without braking. If front wheels were out, you'd feel it on the steering wheel and then the feeling would be different if the buckled wheel or out of shape tyre was moved to the back