Baja Man wrote:
Are there any good step by step procedures or videos you can refer me to?
Are brake drums turned?
When are brake shoes replaced?
Are magnets replaced? How do you inspect and what to look for in terms of wear, required thickness, etc?
Hi,
I'll add some not said already. See this post on the towing forum, it may help
Annual Brake Inspection and Axle Re - Lube (Pic's)To turning the brake drum, this is what I have found, and this applies to trailer drum brakes, not automotive. There are 2 parts on trailer electric brake drums that need to be looked at.
The brake shoe riding surface. There is a minimum wear diameter stamped into the drum. Odds are high with only 10,000 miles on the trailer with manual adjust brakes, you have not exceeded the min. wear. If the drum shoe surface is smooth and not grooved up, then I would not have it turned. I have asked at the local auto parts store if they turn trailer drums. They did, so I asked to tell me what total runout (TIR) of the drum will be turned too? They said it would be in spec. I said what is the spec, they did not know. I said thank you, and left. Trailer drums do not spin very true like autos brake drums. The drum being 0.015" out of round at the shoe surface is acceptable. I have seen some at 0.025" TIR. I'm not keen on that and prefer them to be at least within 0.005" TIR. If you take your drums to a place to turn them, confirm what they will hold them too, or forget it. They may be worse then what you started with. Just spin the drum when you go to adjust the brakes. You will hear a skip and a swoosh as the drum spins. The skip is air touching the shoes, and the swoosh is the lining touching the drum. The drum is spinning out of round and that is the way trailer brakes are.
For sure, adjust the brake shoes as part of the bearing servicing and make sure the adjuster is not rusted up. Unless you have the newer forward self adjusting brake option, they are manual adjust and should be tweaked every 2,000 miles for adjustment. And manual adjust brakes do not wear fast as they wear out of adjustment and the owner never knew to adjust them. Years go by with no adjustment. When they are not in adjustment, the shoes/or drums do not wear much as they are not stopping well, the truck is doing more of the stopping.
The other part of the drum is the magnet surface. I have found, the magnet surface wears more then the drum shoe surface to be a problem. This can come in the 20,000 to 30,000 mile time frame. If you have grooved scored areas in the magnet surface, and the depth of the groove is greater then 0.010", then get the magnet surface refaced or replace the drum. If the groove gets to 0.012" - 0.015" deep, or deeper, you will start loosing braking strength as the magnet needs good full contact to have the proper holding strength. There are not many drum shops that can handle the magnet surface. And a full machine shop can do it, but it may cost more then a new drum. There is a Dexter tolerance on resurfacing the magnet face. I would have to look it up. Something in the 0.030" range, but don't quote me on that.
Dexter states that when the shoes wear to 1/16" of lining, it is time to replace them. Small heat cracks in the linings are considered normal. The shoes are bonded to the lining so it is not a problem. The shoes are not thick when new like the older automotive drum brakes use to be.
The magnets need to be wearing flat and even, not on an angle. A magnet that wears on an angle generally has an issue with the mounting being worn holding it to the magnet arm. And you can't buy just a magnet arm as a spare part, but you can buy new magnets. If the arm is shot, then it's time for an entire new brake plate. Many magnets have wear dots on them, 4 small holes about 1/32" in diameter in the wear surface. When the hole is worn flat and gone, the magnet is considered to be replaced.
When you have the wheels off, look at the trailer suspension and the leaf spring bushings. Odds are high, at 10,000 miles the original nylon spring pin bushings are worn through and you are grinding the pin on the leaf spring. The standard nylon bushings have been known to wear through in 8,000 miles pending dust etc. conditions. Check the shackles for wear, odds are high the equalizer center pin is worn through the nylon bushing and eating into the casting. When the casting is worn, any new bushing in it will wear faster. Replace the equalizer if the casting has wear. They are cheap. When the center pin wears, it starts flexing the equalizer and the shackle links. Flexing shackle links start wearing faster/worse and soon the spring pins in the links start spinning making everything wear even faster. In order to check the nylon bushings, you almost have to pull the pins, and by then, replace the bushings. If you want to keep the camper another 10,000 miles, consider a greaseable bronze wet bolt kit upgrade with heavy duty shackles. When the shackles start wearing from spinning pins, sooner or later they will break the hole out through shackle plate at the pins area and leave you stranded on the side of the road.
Hope this helps
John
John
