Had a bike on the bumper for about 9 years no problem. It was where the spare tire was located.
New rig has receiver and bought a rack to fit it.
One thing that I have noticed with bicycles on back is that they are strapped to the rack but when following one you can see the bicycles sway and bounce. I use bungie cords to stop all movement, ie tires are bungied to bumper. I try to stop all movement of the bicycles.
I may go to the pinbox mount someday because I might put a generator in back.
We used a four bike rack with the Bumper adapter on our last TT without a problem. You do have to insure tiny RV bumper can handle it. We recently purchased a MH and had a front mounted 2" receiver on the front of the MH as we are towing a toad. Seems to work fine and does not obstruct airflow to the MH engine. The front hitch cost us $ 150 which I thought it was a good long term investment as we prefer to bring our bikes along.
I also was looking for a bumper mounted bike rack for two bikes a while back. After so many negative comments I stopped looking. I now am looking at ladder bike racks instead, but I do not know if they make them for 4 bikes.
I wouldn't mount bikes on the ladder. Those ladders are flimsy. Yeah it will hold your weight, But it seems barely. If you look at the ladder design, Thin tubing and all. I would bet bikes bouncing on the ladder, you will quickly see that the ladder starts falling apart. If you can mount the bikes so they don't jiggle, You might be OK but that would be a lot of ball bungees. Try this, Climb half way up the ladder, Have you wife tie you feet and hands to the ladder rungs, Then bounce up and down, I bet you change your mind. But, i have seen it done, and i am sure there are folks that don't have a problem with it. It just isn't going to happen on my flimsy /creaky ladder.
Negative comments, Don't believe everything you read. One guy, or two have issues with bumpers cracking and it turns into policy that it is a bad idea. There are 10's of 1000's of bikes racks on the rear bumpers. There is also storage compartments that people mount on the back for generators. I have even seen 5vrs and tt's pulling jet ski trailers or golf cart trailers
I you are concerned about the thin wall tubing bumper. (I am not but inspect yearly). You can buy a pc 4 x 4 tubing 1/4" wall for about $150 or less. Take it to a welder,unless you can weld. Cut off off the old bumper and install the new one. Then it will be capable of 1,000's of pounds, for ever. Not that i would mount 1,000 of pounds to the bumper, We are talking about Bikes, But it is more for the stiffness. You can also buy the 4 x 4 end caps for the 1/4" wall tubing.
You can run through these pages. Lots of idea's.
Here is a link to a cool thread on all kinds of ideas, My favorite type of threads and post that i have spent many,many hours of going through. Plus i search out more of the same.
Prior to installing the bumper mounted bike rack on our fiver, we also stored our bikes inside. But when traveling on the road, and you want to stop for food, or potty brake, those bikes are always in the way. Yes the bikes stay cleaner inside, but those necessary stops are much easier without the bikes inside blocking the isle.
When we got our 5'er we knew we wanted to take our 2 all-carbon road bikes with us. Our 5'er has no rear bumper so we had a local shop weld a frame-mount hitch right to the frame underneath. We already had a Thule T2 rack for two bikes and that goes right into the hitch receiver. When we reach our destination the rack comes off and goes into the receiver on our TV if the bike trail is a ways away. We've done this on Cape Cod and in Nova Scotia and on PEI so far. By the way, the Thule T2 rack is expandable to 4 bikes.
1991 Avion 30' Fiver, not silver
2006 Silvarado 2500HD Duramax, SRW, CC, Short Bed, 4x4
16K Draw-Tite Slider
Bikes on the back
Standard Poodle inside
Most of the newer RV's that have a bumper can support four light wieght bikes using a previous posted 2" receiver hitch bolted to the bumper. It you have a spare tire on the bumper take it off and toss it in the truck. I have a receiver hitch on the front of my truck so I carry two bikes there. Don't think I would put four. I also carry my Honda 3000 on the front bumper if dry camping and hang my bikes off the ladder. I would never put my bikes inside the RV. Also you may want to check out those receiver hitches people attach to the king pin. I was considering this but my king pin is covered with a fitted plastic cap and I don't want to remove it.
I made the receiver.. 1 1/4" Minor correction, But the picture does make it look bigger. That thing is an old bugger. Done it a ton of years ago. Luckily all my RVs have had the same size bumper. Every time i swap it over, I give it a sandblast and paint. I bought my bike carrier at a yard sale new for around $50. Mine looks kind of like this but without the tilt option> http://www.walmart.com/ip/Advantage-TiltAWAY-4-Bike-Rack/16517833
Thinking about making another, Then i will have two and i can make in a slide in shelf rack for something seeing I am about done with the bike riding.