Break-in period for new Dexter 12" assemblies

[wulfraat]

New Dexter 12" brake assemblies are on... new backing plates, new shoes, new drums, new bearings and new seals too!

Drove 20 miles home from the shop this evening... the new gear provides close to zero friction / stopping effectiveness right now

I found the information below on how to best break-in new shoes and drums from Lippert who supply self-adjusting drums/brakes for RVs that are similar to dexters..... do most people concur on the method below?

Thanks team airstream!


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The break-in period is a typical phenomenon with drum brakes and especially electric drum brakes. Electric drum brakes will require a break-in period to achieve full performance. This break-in period applies for new axles and any time new brake shoes and/or magnets are installed as part of regular maintenance.
Lippert Components has found through extensive brake testing that the break-in period for our drum brakes can range from 20 to 50 brake applications. Brakes can be seated in by applying approximately 8-10 volts to the trailer brakes at an initial speed of 40 mph and allowing the truck/trailer combination to slow down to 20 or 25 mph. For best results do not use truck brakes during this procedure. The trailer brakes will seat -in faster by using them to stop both the truck and trailer. The easiest method is to apply the trailer brakes using the manual activation lever located on the in-cab brake controller. Care must be taken to not overheat the lining material, therefore brake applications conducted at one mile intervals will suffice.

The driver should feel a noticeable difference in the brake performance during this period, sometimes in as few as 10 applications. After 50 applications, the brake lining material will be fully cured from the heat and develop close to 100% contact with the brake drum surface. This break in period not only seats the shoe lining material but also seats in the brake electro-magnets. During the break-in period, the linings will wear at a faster rate than they do after they are seated in.

[dznf0g]

Sounds reasonable to me. Unless shoes are radiused to the drums (which they are not ) it takes some applications to seat them. My experience says it takes more than 50 applications to get to 100%. Adjustment might be needed after seating.

[wulfraat]

Thanks Rich.

[lewster]

Be sure that the brakes are adjusted initially. This will assure tha they wear evenly during their first use. Use the 'star wheel' located at the rear of each brake assemble to tighten the drum so it scrapes the shoes.

Then back the shoes off the drum so they just clear the drum.

After the break-in period, re-adjust in the same way and you should be good to go. I always re-greased the bearings and adjusted the brakes annually when I had my CCD.

[wulfraat]

Thanks Lew. I had the work done at a reputable RV / Trailer / Truck shop here in the denver area (Trans West). They did the initial adjustment all around so I am assuming it was done right

[JCWDCW]

I replaced rear backing plates on my 25, turned and refaced the drums and adjusted similar to Lewster's suggestion. They worked perfectly first time out, much to my surprise. I always adjust the brakes to just tight enough to prevent being able to manually turn the drum, then back off 6 or 7 notches. Should be a bit of drag when rotating manually after adjustment to allow the shoes to break in
JCW

[Jacob D]

I've done this 3 times now on my '67 Overlander. 30 years ago I replaced only shoes, magnets and springs and adjusted to slight drag. Good brakes with original drums right from the start. 5 years ago, after a spring broke and wedged between the drum and shoe I bought 4 full Dexter backing plate/brake assemblies, even though the old shoes and magnets were worn less than half, bolted them right on my original Henschen axles, and reused the original drums which showed no sign of wear or damage. Brakes were perfect from the start. December 2015 I replaced the original 2,800 lb rated Henschen axles with new 3,500 lb Dexter axles complete with 12 inch self adjusting brake assemblies and new drums. To my astonishment, the trailer had almost no brakes at all when I tried it out on a country road. At this point I need to say I am using a vintage Kelsey-Hayes hydraulic/electric brake system. Went back to the shop, checked brake shoe adjustment which was good and adjusted the Kelsey system gain to max and tried again with only a little improvement. I drove the rig very slowly for the next 50 or 60 miles, applying the brakes frequently and gradually got enough braking action that I felt safe in traffic. Now, about 3,000 miles later I am backing off slightly on the gain as brake action is about normal. I will gradually back off on gain as the brakes continue to wear in.

[MelGoddard]

Originally Posted by JCWDCW

I replaced rear backing plates on my 25, turned and refaced the drums and adjusted similar to Lewster's suggestion. They worked perfectly first time out, much to my surprise. I always adjust the brakes to just tight enough to prevent being able to manually turn the drum, then back off 6 or 7 notches. Should be a bit of drag when rotating manually after adjustment to allow the shoes to break in
JCW

6 or 7 notches????
s
Should only require 3 notches or four at the most, to give you that slight 'drag'.