After three thousand miles the front brake on my son's adult tricycle developed a loud squeal. I disassembled the hub and all looks about as it did when it was new. Plenty of material on the shoes/pads. Braking power hasn't changed. The squeal happens at very low speeds, right near the stop. My son is autistic so it drives him up the wall. I can see no grease or oil leakage. I have ruffed up the shoe surface with sand paper, this helped for about a block and a half. I can't find replacement shoes from SA. I guess I could replace the front hub but that seems a bit much. Any suggestions?

Could the spoke tension be off? Unequal spoke tension could be ovalising the drum slightly, which according to the mechanic at my LBS, can cause drum brakes to squeal.

Off Line.. Go have live shop inspection.. Given Portland has a zillion bike shops.
make the rounds..

I have a bike with F/R SA drum hubs, no problems for 25 years..

this may be a not worn in, enough situation..

maybe add a Rim brake, lever, on the other handlebar..

it is not uncommon to have 2 brakes on the same wheel,
on tricycles

Roughing up the surface would have been my first suggestion.
Is there a way to adjust the way the shoe hits the drum? If so, adjust it so the front of the shoe hits BEFORE the back of the shoe. If there is not an adjustment, try swapping the shoes around. After that, maybe get new shoes.

Drum brake squeal can also be caused by a lack of lubrication between the metallic parts of the shoes and any other parts that they contact. Make sure that the following components are properly lubed with high-temp grease:



The backing plate/shoe contact points (if applicable).



The eccentric cam.



The anchor/pivot pin.



The shoe hold-down springs (if applicable).

I don't have experience with the SA drum brakes, but when my Maillard drum brakes get squeaky, I open them up and clean off the pads and drum and it seems to solve the problem.

+1

Never had to, but this is the first thing I'd do: Scotchbrite and alcohol to clean the hub drum surface; light sanding of the brake pad surfaces with fine emery cloth or high number sandpaper. And greasing as FMB42 suggested, above, during reassembly.

I have one (of many) SA drumbrake rear hubs with that issue. And like your son, I'm on the spectrum as well, so yeah, it bothers me. I thank you for asking this question (and the others who answered), so now I can try a few things to fix the issue. Which, BTW, developed after I left the bike unused for two weeks after riding it in heavy rain.

Thanks for the suggestions! I got up early this morning and jumped right into it.
I cleaned and lubed.
Reversed the brake shoes, not an easy task, for me anyway.
Put it back together and out the door.
Squawk!!
And I had such high hopes.
So I guess I'll try again tomorrow.
I don't want to take it to the shop because I actually like working on bikes.
I used to work on my cars, which seems very similar, but I could feel my blood pressure
go up as soon as I lifted the hood.
I didn't sand the shoes this time but I noticed the surface has a patchy glazed surface.
So all the shoe surface is not coming in contact with the drum.
I'll take a picture and post it.
I did find a replacement on the Sturmey site, it looks like I would buy the whole assembly that the shoes are attached to.
If I go that route I may just buy the dynohub and build up a new wheel.

I have that spare assembly with the shoes. It's still cheaper than a (rear or front) drumbrake hub, and probably much cheaper than a new drumbrake dynohub. The very reason I bought the assembly was to save both money (cheaper than new hub) and time (quicker than building a wheel).

As a handicapped individual, he might never really reach speeds that are high enough
to bed in the brakes, which may do better.
after some high speed stops..

like hill descents.. that is understandable..

He is not handicapped, he's just autistic.

And here he is. I'll admit he's not into speed much. Though I have ridden the trike down hill at 27+mph. Scary.
I managed to slice my thumb this morning so I'll wait a bit to take it apart again.

That trike looks similar to the one that was recently stolen from me. I'd be positively scared to ride it at anything approaching 20 Km/h. Because of the way it behaves when turning, it feels like it'll fall on the side when going downhill on anything but the flattest of roads. But it was an awesome go-getter. No problem at all transporting my old 45 Kg monitor to the junkyard.

OK but the issue is Just at the last few feet of stopping ....
small fractions of a MPH rate..

not braking in general.. toe in works on rim brakes for noises
That is why, I suggested the rim brake addition .

Hate the noise?, change hands , to the rim brake operating lever.

the other brake will still be the reliable stopper
till the speed is sub walking rate.

The rim brake does not even need to be powerful, then.

If you're buying parts, I've been able to buy just the shoes in the past, without the rest of the mechanism. They aren't hard to fit.

Thanks for the reply. You are right, the squeal is at about as close to zero as you can get.
I did install a front caliper previously. Just for backup, the original cable to the drum broke early on.
Given my son's autism he would have a very difficult time switching between brakes.

I have found brake shoe replacement kits, in Holland anyway, so I'm guessing they are
around in the USA too.

I did find a nice site showing how to maximize/improve the braking of the drum brake.

https://blog.dutchbikebits.com/2010/1...fficiency.html

Anyway, I will keep at it and report back.

Just a short update. The squeal went away on its own.
I cleaned it several times without success.
Light sanding/buffing helped for a couple of minutes.
I'm guessing some impurity on the pads wore off.
The brake also seems twice as strong as ever.
The trike has been ridden 4000 plus miles,
the pads look to be new.