Help with Summer/Winter Tires.

The diameter variations you describe are of with the central hub opening on the rim? And the wobble you're experiencing is with the stock Toyota wheels/tires? It seems counterintuitive that the stock rims would have problems; had you used them before, and were they ok then?

 

Grant, the aftermarket wheels probably need a lug nut with a tapered face that seats against the wheel. These are lug-centric...centered by the lug nuts on the lug studs.

The factory wheels are hub-centric (centered on the circular protrusion on the hub) and need the factory lug nuts. If you did not get the factory wheels centered and fully seated on the hubs, then the lug nuts can bolt on tight but the wheels is off center--and likely to loosen the lug nuts, and isn't safe. The factory lug nuts slide into the wheel's lug holes, and when everything is centered will firmly clamp the wheel to the hub.

 

Inspect the center hub on the car (not the wheels you took off), I am almost sure what is happening is that the center hub ring that was used for your aftermarket wheels stayed on your car side and did not get removed with the winter wheel you took off. The center hub ring is a black plastic ring that fit exactly the size of the hub on the car and the outer diameter is exactly the size of the larger bore of the after-market wheel.

Exactly the same thing happened to me once. But in my case, I could not install the OEM wheel over the center hub ring, so I figured out what was happening before driving it. See the photo below. A red arrow is pointing to the black plastic center hub ring used for the oversized bore of the aftermarket wheel. The photo below it is on the other side of the car without this center hub ring.