C2/3 brake rotors which actually have runout are rare. Yes, it does happen, but those rotors are pretty robust so it doesn't happen often.
What is more likely than rotor runout is that, at sometime in the car's life, the rivets holding the rotors to the either the front hubs or the rear axles have been drilled out, so the rotors can be removed.
What's important to understand about C2/C3 disc brakes is the rotor friction surfaces were machined after the hubs and rotors were assembled. The assembly is "true" but the hub and/or the rotor, individually, may not be. The rear rotors' friction surfaces were machined after the rotors and the axles were assembled. Again, the assembly is true, but the axle flange and the rotor flange may not be.
This dumb-assed way to manufacture C2/C3 rotor/hub and rotor/axle assemblies has created havoc with servicing those cars' brakes.
You can have a perfectly machined friction surfaces on used rotors which were "turned" or on new rotors, but if the two mounting flanges–hub or axle and rotor–are not perpindicular to their axes, then "rotor runout" occurs.
Another probmem is can be with the rear wheel bearings on C2/C3 disc brake cars. You can have true axles and rotors but if the wheel bearings are too loose, you'll have brake problems such as the OP describes.
What are the solutions? There are many. Shims can be used to "fix" a problem with untrue mounting flanges on hubs, axles or rotors. You can press out the wheel studs then machine the hubs and/or axles to "true" them. You can rebuild your rear bearings such that you have the absolute minimum acceptable bearing clearance.
There are more details in some old articles here on the CAC about C2/C3 disc brake service.
Click here or
click here
