Reese Dual-Cam Hitch

While I was familiar with both the goal, and general appearance of a weight distributing hitch, I had never actually laid hands upon one until it came time to tow my Airstream home from the previous owner’s house.  But since I somewhat live for mechanical challenges, hooking up the spring bars and figuring out how many chain links to drop seemed rather straightforward, and I was on my way in short order.  The groaning & popping of the Reese Dual Cam Anti-Sway hitch while on the road did initially catch me off guard, but seeing as the whole works had sat unused & rusting outside unprotected for the last 23 years I was not alarmed.

Since my Overlander had been towed behind a ¾ ton Suburban similar to mine for the last seven years of its previous camping life, I thought no adjustments would be required for me to open up another chapter in the trailer’s life.  If nothing else, I knew the previous owner had had all his hitch work done at an Airstream dealership.  So other than sandblasting & painting all the hitch’s components, no adjustments were made although I continued to read what others had to say about the setup, and maintenance of this particular hitch.

While it might make sense to some for me to stop and write out a few equations with corresponding free-body diagrams as an aid in understanding the words & pictures below, I believe I will spare you.  Although I enjoyed my Statics and Kinematics classes, that stuff appears to have low general appeal to most.  Unless a lot of people email me begging for [even more] dry detail, I will just stick to the high points of how I arrived at having a properly set up hitch.

There is an Airstream guru in California who, in addition to being an Airstream Dealer, knows what he is talking about.  Once, while discussing what might have contributed to a certain accident, he observed that the Airstream being towed was “over-hitched” to the tow vehicle.  What he meant in his context is that the hitch’s spring bars were too stout for the combination of actual tongue weight and heavily sprung suspension of the tow vehicle.

Now, up until that point, it had not occurred to me that there was more than one flavor of spring bar.  In response to further questioning, the guru shared the secret to determining what size spring bar one might have, “Measure the thickness of the bar at the trunnion.  A 1 inch bar with cam follower has a 550 pound rating, 1-1/8” = 750, and 1-1/4” = 1000.”

After reading this, I went out to the shop and determined that I had 1000 pound spring bars.  Coupled with my Suburban’s ¾ ton suspension, I too apparently qualified as over-hitched.  The Dealer went on to share some other disheartening (but accurate) observations about why this condition was not a good idea, and wrapped up his statements with a remark that he was going to write a magazine article on the topic.  Unfortunately, many months have elapsed, and the article has yet to be written.

Although I continued camping unabated for the rest of the season, the thought that I could be towing smarter never left my mind.  Reading from additional sources, it became clear that Suburban’s suspension did not need spring bars that stiff to distribute weight as its rear springs really don’t settle that much under the unadjusted load.  In fact, it needed the lightest ones made.  I believe the reason the previous owner had 1000 pound bars in spite of having less than 500 pounds tongue weight is because those particular bars would have been suitable for his original tow vehicle – a soft-sprung 1966 Oldsmobile Delta.  When upgrading to a Suburban, the fact that he needed to switch to the smallest spring bars made was either unknown or lost on the dealer who installed his hitch.

The immediate effect of over-rated bars is that there is no “give” at the hitch.  If, for example, the tow vehicle’s rear wheels should want to drop into a pothole, they might not actually drop all the way down because the over-rated bars are strong enough to keep “axis of towing” level.  Since the Airstream’s frame is not as stiff as the Suburban’s, the Airstream will suffer.

Reese changed the spring bars’ style at some point.  Doing away with the bolted-on cam follower, they elected to make a bend in the steel.  Other than the bar being a bit longer than the old style, the new style looks like it would do the job.  But at $300 a pair new, I turned to eBay for some used ones.

Odd story there:  It took very little effort to find an item with “Reese 550 Weight Bars” in the title.  The two, used spring bars pictured appeared to be what I was looking for, and they were complete with cam followers.  So I bid on, and won them for not much money.

Measuring the bars after they arrived, I found them to be 750 pound bars.  Alerting the seller to this fact, I asked her how she wanted to proceed.  Advising me of her current credentials in the RV business, she tried to tell me the bars would work just fine.  This statement was especially interesting because I was never asked what kind of truck or travel trailer I had.

I replied back that no, I would like to have the purchase price & shipping refunded PLUS the cost of shipping the bars back to her.  She said okay EXCEPT just keep the bars and/or throw them away as she was not supplying return shipping fees.  A satisfactory email from PayPal arrived soon thereafter so I logged on to eBay and left the seller positive feedback.

Renewing my search for the proper spring bars, a just-listed auction presented itself.  While the spring bars pictured had no cam followers, I knew that the ones on the 750 pound bars would work on them.  To be on the safe side, I decided to email the seller & ask for a measurement.  Guess who the seller was?  Yep! - The one who had just refunded my money.  After thinking about it a minute, I went ahead and posted my question.  Getting the answer I wanted to read, I bid on & won this pair too… for a few bucks less than the last set.   And yes, this time the seller shipped me 550 pound bars.


An interesting thing about both the 750 & 550 pound bars is that both sets had a gentle bend in the loaded axis in each bar that does not exist in my 1000 pound bars.  An unloaded bend in high-grade spring steel means the metal has yielded, and is pretty much done for.  But it takes a tremendous force to accomplish that.  All four of these bars just looked like they had been left in a loaded position for an extended period of time, and had acclimated to their present condition.  Since Reese Australia allowed that spring bars can, over time, develop a gentle bend that does not hurt anything, I decided that the bars are not made of a high-grade spring steel and there was no reason to go in search of an unbent set.

A properly loaded spring bar, i.e. a bar installed on the hitch & under a weight distributing load, should deflect at least one to two inches according the guru.  The bend is measured by placing a straightedge on top of the bar & measuring the distance between it and the bar.  The bar can apparently be deflected up to five inches without suffering damage.  The whole concept of a visible bend was new to me as my 1000 pound bars were never anything but perfectly straight.  I even adjusted it too tight once to see if the bars would deflect, and the only thing that happened was the back of the Suburban sat too high.

Around the time all this eBay activity was being conducted, we headed out on a long distance trip to the beach with the Airstream in tow.  The Overlander seemed to suffer a lot of vibration issues on the trip.  Deciding the bulk of the blame was probably attributable to the original axles I was still using; new, complete axles were installed while the “new” 550 pound spring bars were being painted a “Sixties Airstream” color.

If I had wanted to be a good scientist, the new spring bars would have been installed and reported on before the new axles were installed; or vice-versa.  But with another long distance trip scheduled for only a couple of weeks away, it was more important to have the Airstream in the best possible towing condition.  So the two were installed back-to-back.

In a properly set up Reese Dual Cam hitch, both the tow vehicle & Airstream will ride level, and the spring bars, except for their prescribed bend, will be parallel to the trailer frame.  The picture at right shows the original drawbar with the new 550 pound spring bars.  As you can see, the spring bars are far from parallel to the trailer frame.  Also notice the adjustment chain near the left of the picture dangling free.  While only slightly less than an inch of deflection was required to level the Suburban, I ran out of links which would safely hook.  What the picture does not show is the Airstream nose-diving somewhat due to the additional 1-1/4 inches of height picked up after the new axles were installed.

Adjustments obviously needed to be made, but they had to occur at the drawbar, and if you look closely, you will notice my drawbar is welded-together.  I assume custom making a drawbar used to be the only way to get one.  While eBay sells the necessary piece-parts, it does not appear to be done much anymore.  Luckily, I had another drawbar that could be used, and it was fully adjustable.  Following Reese’s setup directions, I arrived at the configuration shown in the picture at the top of this page.

Two things uncovered during the set up I was previously unaware of are worth mentioning.  One of my original 1000 pound spring bars is about a ¼ inch longer than the other.  Since the relative positions of the cam saddles are fixed, this would make a difference in the anti-sway function if the bars were interchanged.  Upon further inspection, one of the bars is either a very old Reese bar or another brand altogether, although I have no idea of who it would be, because it has only one hole in the end instead of two like my other five bars.

The other thing noticed is that my Overlander’s A-frame is bent upward.  After thinking about it, I believe this was a direct result of running with too-stiff spring bars.  Since, like I mentioned earlier, the Airstream’s frame is not as stiff as the tow vehicle’s, the Airstream will be the loser when bad road conditions are encountered.   A bent A-frame is the manifestation of the damage.  Fortunately, I believe ‘bent’ is all it is as much time was spent working on the Overlander’s front frame during the refurbishment, and no cracks in either the steel or welds were found.

The results of going to lighter-weight spring bars were remarkably noticeable, and could easily be differentiated from the new axles’ contribution to an improved ride.  On our first trip, I had barely made it out of town before noticing that the Suburban had a gentler feel overall, and my teeth were not jarred when going over railroad tracks or potholes.  Allowing the Airstream to move independently of the Suburban while negotiating adverse road conditions was definitely the right thing to do.  On the interstate, the anti-sway capabilities of the hitch showed improvement – I had apparently been riding around for some time with the old bars swapped.

And now that it is all said & done, I am the only one I know who has a complete collection of Reese spring bars.