Sierra Nevada Airstreams - Owner's Guide - Maintaining

Recreation with vehicles in the Sierra Nevada and American Great Basin areas

Hitch Setup

A hitch setup for towed vehicles is a mechanical and electrical connection with failsafe measures. For any non trivial situation the hitch needs to distribute vertical loads and control horizontal movement. Proper rigging is essential for the safe operation of your RV!

Is that coupler latch really down? There seems to be a lot of slack in the chains, lanyard, and electrical cable.

Prevent Op Malfs

The most common reasons for hitch separation underway seem to be operator malfunctions: a failure to seat the coupler on the ball and lock it properly; a ball that becomes loose due to improper nut torque and a lack of inspection; failure to pin the shank in the receiver. Something actually breaking seems rather rare.

Good checklist procedure and verification can minimize the risk of hitch failure. Don't let anyone interrupt you when going through your hitching procedure! Check and recheck.

Verification means using redundancy, testing, and inspection. For example, raising the hitch to set spring bars will only work if the ball is locked to the coupler so that the entire hitch is raised. You will know right away if your coupler lock was inadequate when you try to set your spring bars this way.

Planning failsafe

The hitch has two devices intended to serve in case of failure. Chains connect the trailer to some part of the receiver or tow vehicle frame not a part of the ball assembly. A breakaway switch with a lanyard attached to the bumper is intended to set the trailer brakes if the trailer becomes separated from the tow vehicle.

Chains need to be strong enough to support the tongue of the trailer and the inertial forces involved in the breakaway event and in slowing the trailer to a stop. They are usually crossed underneath the ball (this is sometimes also a legal requirement) so that they can be short enough to keep the tongue from hitting the road yet not bind during turns. If the hitch fails, shorter chains will prevent the tongue from flopping around which provides better control in an emergency situation.

Depending up the failure, the spring bars may also be a concern. If the ball falls off and the coupler slides back, the spring bars will tend to hold the tongue down. If the ball mount comes loose they will tend to rotate the receiver bar down. If the spring bars become loose, they are another part scattered on the road. If they stay attached, they may be dangerous to release.

The relative lengths of the chains, the breakaway switch lanyard, and the electric signals and power cable are subject to some debate. In the first phase of a hitch failure, a set of chains takes over for the ball and coupler that failed. The second phase may be (a) a manually controlled stop or (b) a trailer emergency stop or (c) a chain failure requiring additional backup. It seems to be your choice and is determined by the lengths of the electrical cable compared to the breakaway switch lanyard. Some brake controllers may malfunction if they are connected and the breakaway switch activates. There may be a fear that the sudden applying of trailer brakes via the breakaway switch would snap the chains. Here are some other things to think about in deciding how you want to handle a hitch failure.

  1. The critical issue is adjusting the chains so that you can keep good control of the front of the trailer. You don't want total separation if there is any way to avoid it. (or do you?)

  2. You will not likely be in an emotional state for rational behavior if your hitch fails.

  3. If there is complete separation, you want the trailer brakes activated to bring it to a stop as soon as possible. Then you can take a deep breath, collect the pieces, and clear the road.

  4. If you worry about weak chains, get stronger chains and make sure there are no weak links and that the connections to the receiver are properly rated.

  5. You will want your trailer to slow to a stop so you will need to either have your controller set properly, depend upon a breakaway switch, or be able to manually control the trailer brakes if you can quickly summon a proper presence of mind. The chain worry is transferred to worrying about too much trailer braking.

  6. The electrical power and signal cord with likely not disengage gently but will likely tear something if pulled loose.

  7. The breakaway switch should be de-activated within 5 minutes or so to prevent trailer brake magnet overheating and other problems.

  8. There are those who suggest that you should not padlock your hitch ball latch because that would get in the way of an emergency release. Others like the security and feel that emergencies need to be handled in other ways.

Hitch adjustments

There are a number of hitch adjustments that work together to spread the tongue weight of the trailer to all axles. Dallas (WBCCI/VAC #8481) puts it this way:

Adjust the hitch ball height to 'level' the trailer
Adjust the weight distributing bars to 'level' the tow vehicle
Adjust the hitch head angle to 'level' the bars.

If your ball mount is welded to the shank, adjusting the ball height and angle can be rather difficult. This is why using a 'L' shaped drop bar shank with holes about every two inches is handy. The ball is mounted on a bracket that is bolted to the drop bar and its height is easily adjusted. The ball angle can also be adjusted with a spacer on the top of the ball mount between it and the drop bar and an adjusting nut at the bottom to hold the mount steady.

Many weight distributing or spring bars are connected to the trailer frame with chains. The tension on them is set by the number of links under stress. This adjustment allows tuning the spring bars for load, if necessary, but the spring bars should always be fairly close to parallel with the trailer frame to avoid binding on the frame or dragging on the ground. The ball angle is the first control for spring bar adjustments.

Trailer hitch parts are big and heavy. Nuts and bolts often require half or even three quarter inch drive sockets. You don't use crescent wrenches or water pump pliers on these! A 2-5/16 ball with a 1-¼ shank rated for 5,000 to 10,000 pounds is specified to require 450 foot pounds of torque tightening. That takes a lot of oomph. After you get all of your adjustments right, make sure that the nuts and bolts are properly tightened with good tools. Then check them at least annually to make sure that nothing is working loose.

In most cases:

  1. The ball mount, which includes the spring bar bracket, is tilted about 5 degrees to the rear. This angles the spring bars down so they will have tension on them when pulled up parallel to the trailer frame.

  2. When the coupled hitch is raised about 6 - 8 inches, the spring bar attachment to the trailer frame will have no load and can be easily connected. If you need less than about five inches to relieve spring bar tension or more than 9, make sure you have the proper spring bars for your tongue weight and have the ball height and angle set properly.

When adjusting a weight distributing hitch, the easiest measure is to measure the heights of the wheel fenders above ground before and after hitching. A proper setting should cause all fenders to settle the same amount. But sometimes, especially for tow vehicles that are heavy in front, you may need to actually weigh the axles before and after to make sure that the tongue weight is being properly distributed by the hitch mechanism.


Rig handling involves solving problems of side to side motion called sway and up and down motion called porpoising. Sway is usually inhibited by hitch design. See the Owner's Guide references below for more about various hitch types and how sway works.

Porpoising is a problem on concrete roads when the expansion joints are just far enough apart compared to your wheelbase and speed. The bounce from the joints is just right to reinforce the rig bounce as it goes down the road. Sometimes this porpoising can be reduced by removing spring bar tension on the hitch which allows it to be more flexible. A better solution would be to make sure that the spring bars and the tow vehicle axle springs are properly rated for their loads and to install good shock absorbers.


Owner's Guide: Hitch terminology - Sway - Understanding Trailer Sway.- departure checklist -

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