Adding Hitch for Bike carrier on rear??

GrandpaKip wrote:
I added a frame mounted cargo tray to our camper. When 100 pounds was added the tongue weight decreased by only 20 pounds or so. Don’t remember exactly, but was less than 25 pounds. I think that 4 bikes “could” reside there if loaded creatively.
The problem with most bike racks is the bounce from a receiver mount. Someone on this forum had a double receiver built for their trailer mounted to the frame.

Not sure what you did but something is off with this. Should be more like 60-80lb off the hitch depending on the exact lengths involved.

Let's run some numbers on the OP's case.

He didn't provide the exact model, but let's say he has the 30U model.
- GVWR 7500
- 13% hitch weight (975lb)
- Based on pictures, the center of the axles sit approximately 60% of the overall length from the hitch. 33ft total length with a-frame.
- Let's assume 5 bikes at 30lb each plus the hitch weighs 200lb total and the center of gravity of the combined mass is 3ft behind the back of the trailer.

The moment arm created around the center of the axles by the bikes/rack:
- Back of trailer is 13.2ft behind the axles, plus an additional for the rack 3 ft (16.2ft total)
- 200lb * 16.2 = 3240 ft-lb applied to the axles.
- Hitch is 19.8ft ahead of the axles.
- 3240/19.8 = 163lb off the hitch.

975lb - 163 lb = 811lb (10.8% hitch weight)

This is around the lower limit recommended but likely will be OK but presumes you are starting at 13% hitch weight. If you start at say 11%, you will drop to 8.8%...that's getting into the range where trailers often become unstable. Minimum hitch weight is usually suggested at 10-12% minimum with 15% desirable.

Now if you have the ability to repack some of the gear inside the trailer to move heavy items toward the front, you can compensate but it would be a good idea to swing by a CAT scale and get the real numbers before bolting on and hoping for the best.

With the CAT numbers, you should be able to take accurate measurements and rerun the same calculations for a more accurate estimate based on your specific trailer.

PS: 5th wheels are more tolerant of weight hung off the back. The wheels tend to sit further back with the goal of 20-25% hitch weight. The result is for every pound on the rear, less weight comes off the hitch plus you have a much higher hitch weight to begin with, so the percentage loss is smaller. But even with 5th wheels, something like a full size motorcycle gets questionable. A few months back, someone was asking about putting lead shot as ballast into the front to compensate for it getting squirrely after adding a large rack with full size motorcycle on the back.