Just a thought.......

Is it possible to use a full size tire and rim and deflate it, either entirely or partially, to fit the wheel well. Of course, you would need to carry a small compressor.

 

I don't know, maybe yours is different. The spare tire well in my HHR is 21 inches across at the flat spot in the bottom of the well. (side to side, front to back is different because of the battery) The "mini spare" is all that fits here.

Now, the side walls do taper considerably and a larger tire would fit without going all the way to the bottom and, I would guess, wedge in there securely, but you wouldn't get the cover back on which negates the flat floor, the stock hold down clamp would be useless, and also leaves the battery in the passenger compartment (not that the plastic shield does much, but the factory spec does call for said shield)

So, in my HHR there's no room for a full size spare, inflated or not.

 

O'k...Thanks....

Frankly, I haven't been in that tire/battery compartment in 6 months, so, at my age, I couldn't remember what it looked like. Probably should check the tire for air. Although, when I do check it it is usually around 50-55 PSI. I "top" it to 60.