Yeah I think you’re right that UE4 doesn’t provide this flexibility on the level of individual pairs of bodies. They do something similar for kinematic actors (search ‘MoveIgnoreComponents’ in the engine), but not for simulating bodies it seems.
I’m guessing you’re doing custom physics so not using constraint components/PhysX joints between wheel and chassis? Since in those cases there is a flag available to disable collision between the two bodies constrained by the joint.
Just occurs to me that you could still try a horrible hack - set up a constraint between them anyway, check it’s ‘DisableCollision’ flag, and then configure it as a null constraint that doesn’t constrain any degrees of freedom. Not tried myself, don’t know if it would work and it would probably have a minor performance impact if it did, but worth giving a go.