Class C Ford E-450 chassis spare tire -- or lack thereof

The rear bumper may not be the best choice,although some RVs have them.
Mine is mounted inside my large rear storage compartment,bolted to a frame that is welded to the frame rails.

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Another way to go is mounting the spare using the receiver.

Here are some examples

Or you can mount it underneath

Like Baja Man did

I also carry roadside assistance,to have them do the replacement.
If you don't have your own tire you are at the mercy of them to get one for you and that is really expensive.