On our E-350 2012 Nexus 24' C I mounted the typical bumper mount spare tire holder to our square rear bumper.... After a couple of thousand miles through pretty close to every pothole between Tucson and Maine the mount fractured leaving my spare leaning back at a 45 degree angle. Fortunarely I caught it in time, moved it to the cab over and got on down the road.
I have yet to ever encounter a bumper mount spare tire holder any sronger than the one I mounted and it quickly failed. The physics of this equation simply dictate failure. The leverage imparted by the weight of a spare combined with the bumps and motion of being located on the rear bumper guarantees a a disaster and probably sooner than later.
We solved the problem {after the failure} by stopping at the Nexus factory in Elkhart {which we happily were passing by} and had them custom weld a spare tire mount up under the rear of the coach. The weight is down low, very secure and out of the way but ready for deployment when we need it and there is no question that some day we WILL need it.
A couple of decades ago the auto industry decided that no one needed a real spare and the little mini spares began appearing in trunks across the nation. These are garbage, probably the worst idea to ever emerge from Detroit and it remains a concept {less than a real spare} embraced by the RV industry {because it saves them money to not install a proper spare}.
IMHO: Get a proper spare, fully mounted on the appropriate wheel and then... get on down to Harbor freight {or wherever} and buy the tools necessary to change said sapre - Bottle jack, jackstands, lug wrench, chocks, tire reparir kit and a compressor is a nice touch. Practice at home in your driveway and hope that when you call your ERS they arrive promptly {not likely} change your tire and send you on your way but... knowing that in a pinch you can get it done without them.
As always... Opinions and YMMV.
:C
