This is my answer to those expensive RV skid wheel installations. It hasn't failed me yet.

The wheel is the standard heavy duty steel wheel swivel caster from the the hardware store. The U-bolts, alas, had to be made from 1/4” rod, threaded on the ends. (I notice here that I need to spritz the ends with a bit of paint.)

The standard plumbing guard was in the way for the new “Dumping Facilitator” valve described elsewhere. It also hung down so far as to hit my driveway when we pulled out. If you run a taut string from beneath the left rear tire to the bumper, you can see what's needed near the bumper to prevent the plumbing from hitting the ground. These wheels more than make up for the missing stock guard but have somewhat more ground clearance than before.

You can conjure up some hazards that would be protected by the stock guard but not by this. Driving off an 8” curb, for instance would probably take out your plumbing. But in this regard, we're in no worse shape than some of those RV's with 8' overhangs. You just have to be careful. So far, we haven't even scraped the paint off the wheels yet.