Originally Posted by CrawfordGene
I think there's some confusion what a "major brake" is. As I understand it this is an inspection of the brakes, not a "brake job" as Airslide called it.
To me a brake job is a general term meaning replacing shoes, springs, etc. I believe the magnets go first, later the shoes. When replacing shoes, best to replace springs too. At that point you might as well get the entire brake assembly as it's cheaper than the parts and you can now get self adjusting brakes.
Self adjusting brakes have been around for decades, but just appeared in the RV industry, or at least the Airstream part of it. My experience is that the brakes should be adjusted frequently, maybe 5,000 miles. Of course, every time you remove the drum (hub), you have to adjust them when you put everything back together.
In the RV industry, a major brake consists of the following.
Inspect the position of the axle torsion arms.
Place the trailer on jack stands.
Observe that the tires dropped about 3 inches from their loaded position.
Remove all 2/4/6 hub and drums, with the wheels attached.
Remove the grease seals.
Remove all the bearings.
Clean the bearings in a grease cleaner.
Inspect all the bearings for rust, pitting, wear, and discoloration.
Pressure pack the bearings, with a high quality grease, and set them aside.
Remove all the grease from the hub.
Remove all the grease from the spindle.
Inspect the spindle for an unusual wear, or discoloration.
Clean all traces of the grease from the hub.
Clean the drum face and the armature plate.
Inspect the drum face and armature plate for unusual wear and/or scoring.
Sand the drum face and armature plate, with about 150 grit sandpaper, to remove the glaze on those 2 surfaces.
Inspect the condition of the brake magnet, the brake shoes, the brake springs, and the brake adjuster.
Clean the entire backing plate, and the good parts.
Replace any of those parts, if necessary
Replace the adjuster springs if they are 10 years old or so.
Deglaze the brake lining with the 150 grit sandpaper.
Balance the tire and wheel, along with the hub and drum (when possible).
Install the inner bearing.
Add a little more grease to the bearing.
Install a new double lipped grease seal that also has a spring in it.
Reinstall the hub, drum, tire and wheel assembly back onto the spindle.
Add a little more grease to the outer bearing.
Install the outer bearing.
Install the bearing retainer bushing or washer.
Install the bearing retainer nut.
Tighten the bearing retainer nut, while slowly turning the wheel. Tighten to take all the side play out of the wheel, etc. Back off on the retainer nut, until you can just feel a litlle side play in the wheel, and align the hole in the bearing retainer nut with the hole in the spindle.
Insert a new cotter pin into that hole.
Fold the ends of the cotter pin, over the sides of the bearing retainer nut.
Reinstall the grease cap.
Adjust the brakes.
Lower the trailer back onto the floor.
That, is a major brake job.
It takes, ball park, 3 hours, plus or minus, on a tandem axle trailer, to complete that job, depending on how many parts may have to be replaced. Balancing time is extra.
Yes, that is a lot of work. But that work, assures proper performance of the running gear, along with it's safety.
Performing the major brake job, at it's required intervals, will give the trailer maximum life from it's parts, assures excellent braking, and more than likely, no brake problems.
A couple of those steps, can be eliminated, should the trailer be equipped with "self adjusting" brakes.
The procedure is almost the same, for a major brake job, on disc brakes.
Please note, that some infinitesimal steps included in the performance of a major brake job, were not listed.