U-Bolts breaking during installation

Stratacter wrote:
The manufacturer is a major supplier of trailer hitches, but I won't reveal the company because I'm waiting for them to respond to my inmail on their website. I carefully followed their installation instructions. Also, I'm a Senior Engineer by trade, so I know what I'm doing.

The primary lateral support for the hitch is from the 2 square U-bolts that are fed through four 1/2" holes drilled into the two frame rails that hold the bumper shocks. I drilled the 1/2" holes to match and line up with the hitch holes. Four nuts with 4 conical washers are supposed to attach to the 2 U-bolts to hold the hitch arms tightly against the frame rails, with each nut tightened to 45 ft-lbs.

In my case, I hand tightened the nuts and then proceeded to tighten (with torque wrench) the first nut, and POW, it broke before it reached 45 ft-lbs. Apparently, the square U-bolt was not Grade 8, and the parts list confirmed this. Only the bolts and nuts holding the front of the hitch to the bumper shock frames, as well as the nuts for the U-bolts are Grade 8.

I decided to bolt the hitch, as per the directions, instead of having it welded on, because I'll only use it to support a platform with bicycles, not pulling a camping trailer or anything really heavy.

I hate to think about how many hitches like this were sold and installed, with their U-bolts about to break and cause a serious accident. Many probably already have.

Any recommendations?

It would help if you also posted a couple pictures. Is this hitch being installed on the back of a trailer for a bike rack, or back of the TV.