Friday, March 18, 2011

Strengthen Your Hitch

If you tow a vehicle with your Lazy Daze, you should periodically check under the bumper at the mounting bolts. There have been problems with the bolts that hold on the towing receiver loosening and/or snapping off. You may be surprised that all four or some of the ½" bolts have worked themselves loose. In more severe cases, the bumper itself can be bent and even break apart requiring major surgery and reinforcement. 

There may be a design flaw that causes the nuts to work loose. The rear bumper is attached to the chassis frame by u-shape steel extensions with the receiver being secured to the bumper with four bolts, the front two being 3/4" diameter vs. the forward ones that are a smaller 1/2" diameter. The extensions have slots that allow a range of adjustment when the bumper is mounted at the Factory. Unfortunately, the slots are too wide and high for the hardware used. On the passenger side, the slots are 2" wide and 11/16" high. The Factory uses grade 5 bolts with thin flat washers and lock washers. What happens is the oversize slots allow the thin flat washers(.090" thick) to cave in, taking the tension off the bolts and allowing the bolts to loosen more until the bumper is floating free. In this case, only the nine ¼" bolts that hold the front edge of the bumper to the rear of the body keep the bumper from leaving. You can see where the bumper flexes around each of the small bolts in these photos.

The problem is mostly seen on rigs that use hitch adaptors that raise the attachment point for the type of towbars that stay on the RV.
The receivers are designed to resist down-forces but not for heavy up-forces, On the receiver, when the adaptor is used to raise the hitch, a lot of leverage is applied to the smaller rear bolts under hard braking.

To strengthen the system, the grade-5 hardware can be replaced with much stronger grade-8 bolts and nyloc nuts. To overcome the problem of the oversize slots, make plates out of 1½" wide X ¼' thick steel strap that sandwiches the bumper and extensions together. With the nyloc nuts, even if the bumper bolts loosen, the nuts will not come off.
If you tow, you should check the bolts regularly. The bolts that hold the u-channel extensions to the frame should also be checked for tightness. For good measure, use Loctite thread locking fluid to secure the rear nuts and bolts. The rear of the extension does not have slots and is not subjected to the same loosening problem.

The best solution is to replace all of the hardware with grade-8 bolts and nyloc nuts and to add either thicker, wider washers or go the extra distance and do what is mentioned above. Parts will be around $12.

Going a step further, one can strengthen the hitch by replacing the bumper hitch with one that is more securely attached to the frame. Basically, the receiver is removed, a doubler installed over the existing bumper plate, forward of that are 2 braces that run forward to the frame with a couple of cross beams along the way. Install a different, and easier to use, hook bracket for the safety chains. This should increase the weight limit to something in excess of 5000lbs. $600-$700 for the job.

Contributors: Larry Wade, rstotz

Updated 4 Sep 2014