Dexter Self-Adjusting Brakes and Brake Shoes

[danemayer]

We've just gone through a frustrating experience with our brakes and I thought I'd share what was learned so others might save some worry and frustration.

Our 2011 Rushmore came with Dexter 7000# axles and self-adjusting brakes. Heartland switched from Lippert to Dexter in late summer 2010, a few weeks before our unit was built.

At about 6000 miles, the braking started feeling weak to me. It was taking longer with more foot pedal force required to stop the rig. I called Heartland Customer Service and was directed to Dexter. Dexter agreed to pay for mobile service and selected a truck/RV repair shop to do the work. They found the brake adjusters needed to be adjusted about a full turn. That improved the braking back to normal. But they also found the drums were out of round. Dexter wanted to get the parts back and sent new drums and new brake assemblies (and new bearings). After all parts were replaced, we had very weak braking, perhaps worse than the original problem.

I spoke with a Dexter engineer who asked me to try a break-in procedure, applying the trailer brakes by themselves 50 times, slowing from 40 to 20MPH, with about 1 mile in between braking. After doing so the brakes are working more normally, but I now have the controller set at 7.5 instead of 5.5 to 6.0. I think braking will continue to improve as we travel.

I've learned the following:

1. The self-adjusting brakes may not self-adjust.
2. The adjusting wheel is a bit difficult to push from inside because of the way the ratchet locking lever is mounted.
3. The composition of the brake shoes is such that a lengthy break-in is required.
4. The engineer explained that the self-adjusting mechanism is supposed to work while braking in either direction (and in fact, examining the old brake assembly, you can operate it by hand and see the mechanism adjust in a forward direction.
5. If you ever have the brake assembly out, it's not obvious how the rear shoe gets pushed out. In a forward direction, the front shoe is directly pushed by the magnet's movement when in contact with the rotating drum. The engineer explained that as the front shoe contacts the rotating drum, it is dragged a little, and pushes against the spring-loaded adjuster, which in turn pushed the rear shoe against the drum. (This is not obvious when moving the brake assembly parts by hand).

Anyway, I hope this information helps someone.

 

[Ray LeTourneau]

Thanks for that info Dan. I was playing with a demo backing plate at the rally seminar and your explanation helps me understand the mechanism now. At the time, it seemed that the action of the magnet moving the arms would not go far enough to cause the adjuster to fully move one notch. I'm still undecided though. I have only adjusted my brakes once a year when I do bearing maintenance and that seems to be adequate.

 

[robnmo]

Interesting thread, here's our experience which started yesterday. I decided to pull the hubs and hand pack the bearings (I DO NOT LIKE ez lube hubs). The 1st hub I pulled parts literally fell out on the ground (self-adjuster, cable, spring). I called a Dexter rep in Cincinnati, they had the complete assembly in a 7K, while down there, was talking with a very knowledgeable service rep, they absolutely love ez lube hubs, make lots of money off them due to bad bearings, blown seals, burnt pads, etc. They had no clue what would cause our brake failure like we had on the one wheel other than a "possible" NOT adjusting the brakes before leaving the factory and having too much slack in the self adjusters letting things come loose but even that was very "'iffy". Great dealer, even gave me 2 manual's of parts, numbers, etc, checked the drum, bearings, etc and made the comment that pulling the hubs once a year to hand pack bearings will save alot of problems with brakes, they also showed how to adjust the brakes when 1st installed to keep the slack and slop out of the self adjusters to avoid that 40 to 50 brake applications like the Dexter manual talks about. I ran out of daylight today but got 2 axles done should finish the last one tomorrow AM and hopefully get on the road to Florida by the end of the week.