Need coaster brake shoes for old Soviet bike

[vitataxman]

Hi, I am repairing coaster brakes on an old Soviet bike. I don't know brand of bike (Russian letters?) and there are no markings on any component of the hub/brake. Brake shoes are quite worn and I would like replace them. See photo of bike and shoes. Any idea what kind of shoes these are, and where I might find replacements? Thanks for any help.

 

[tyred]

I don't think they should need replacement. They expand against the hub shell. It should have enough adjustment and needs to be built up with high melting point grease.

It's been a while since I serviced a Sach Torpedo on my Batavus so can't remember too much about it but Sheldon Brown explained it better than I can - https://www.sheldonbrown.com/coaster-brakes.html

 

[Drago]

I can't see that well, but they don't look unduly worn.

There are firms out there thet re-line brake shoes for classic cars and the like, I can see no technical reason why they couldn't re line these for you if it was required. Vintage motorbikes used a similar type of material I believe and were often greased, so I doubt this would be a challenge for such an outfit.

 

[tyred]

The braking surface is metal and they don't have a replaceable braking surface like normal drum brakes.

The Eadie Coaster hub which you might find on pre-war bikes (I have one in my '37 Humber) has similar actuation but has a separate brake drum and works similar to a normal drum brakes, but has brass shoes rather than a replaceable friction material. Mine didn't work and I came to the conclusion that it was the brake drum and not the shoes that had worn out of spec. I fitted a shim to take up the wear and it works perfectly now. Obviously this isn't ideal but for only light and occasional use, it is fine as there is still plenty of metal left on the drum.

 

[Drago]

As aforementioned, many old vintage motorbikes had a metal friction surface designed to be packed with grease amd they can be re "lined." I've no idea of the process involved, as I've never personally owned a motorbike or that age, but it can be done.

 

[raleighnut]

That's a 'roller brake' no brake shoes involved

 

[a.twiddler]

That's a 'roller brake' no brake shoes involved

Beat me to it! Did the OP try it on the road to see if it worked before dismantling it?

 

[FrankCrank]

I'm a fan of coaster brakes, have experience of a few now.
I thought that was a coaster brake when I first saw it, but now I see the additional rollers.
Does anyone have knowledge/experience of both types, in what way does a roller brake behave in comparison to a coaster?

 

[raleighnut]

I'm a fan of coaster brakes, have experience of a few now.
I thought that was a coaster brake when I first saw it, but now I see the additional rollers.
Does anyone have knowledge/experience of both types, in what way does a roller brake behave in comparison to a coaster?

A 'coaster' brake simply refers to how the brake is applied i.e. by 'backpedalling' so no cable is needed.

Roller brakes operate by a cam pushing the rollers against a drum much like a stud extractor.

SAAB used a similar principle for their 'freewheel unit' on the 96 and very early 99

 

[fossyant]

Maybe Cycle Chatski could help.

 

[vitataxman]

Adding some more pictures of the internals. Don't know the proper part names, so I'll call the brass piece that sits inside the shoes the "under-shoes-piece". Here is my guess of how things work with this machine (corrections welcome; this is mostly new to me). When the sprocket (driver) is pedaled forward (by about 20 degrees), the 5 rollers (you can see 2 in the photo) on the driver clutch jam, push out and lock the driver to the hub. When coasting, the rollers are free to roll so the hub spins independent of the sprocket. The piece with the rollers on the driver moves out toward the sprocket (when pedaling forward) and in (when braking) on the threads of the driver, but can only rotate about 20 degrees either way before the rollers jam. In both drive and coast state, the driver is not applying force to the under-shoes-piece, and thus the shoes are not pressed to the hub. The band spring wrapped around the shoes holds them against the under-shoes-piece. The under-shoes-piece also has rollers (2). When braking, the driver moves in and presses into the under-shoes-piece and the shoes ride up on the angled surfaces of the brake cone on one side and the under-shoes-piece on the other side, and thus press against the inside of the hub. At the same time, the under-shoes piece rotates slightly (because of the direction on force from the angled surcaces where it meets the driver) which causes the rollers to jam and lock the shoes to the under-shoes-piece.

I don't have a good feel for how much "rib" should still remain on the shoes. I'm including a side photo of one of the shoes. Is there any sort of spec or rule of thumb on how much rib should remain?

The reason I want to replace the shoes is that it takes a lot of force to stop the bike, the shoes appear to be worn (to my amateur eye), the inner shell of the hub looks OK (but hard to tell) and there doesn't appear to be any adjustment.

Thanks so far for all the helpful input.

 

[a.twiddler]

It's hard to know how much wear has taken place without knowing the original dimensions. If it's a Soviet product, it might be a knock off of a similar bike produced in Europe at that time. Think Ural/Dneipr motorcycles still on sale decades after their originals, 1940s BMWs, had been developed into modern machines. The trick is finding out what the original was on which it is based.

 

[tyred]

Adjustment should be related to the cone adjustment and the position of the reaction arm.

They don't have great braking power in my experience but are predictable, easy to modulate once you get used to using it and completely unaffected by weather. A front brake will always stop you faster.

I'm just looking at your pictures again. You don't appear to have a front brake (or have I missed something). If you're in the UK, you need one to comply with the law.

 

[vitataxman]

Correct, there is no front brake, only a rear coaster brake. I can't say whether the braking of this bike was any easier when it was new. The owner of the bike is a person uncomfortable with the current braking performance, so I'm trying to make it better for her. If new/better shoes can't improve the braking, I'll consider swapping out the hub/brake assembly

 

[FrankCrank]

Adjustment should be related to the cone adjustment and the position of the reaction arm.

They don't have great braking power in my experience but are predictable, easy to modulate once you get used to using it and completely unaffected by weather. A front brake will always stop you faster.

I'm just looking at your pictures again. You don't appear to have a front brake (or have I missed something). If you're in the UK, you need one to comply with the law.

I may be wrong on this, so please correct me if so.
My understanding of UK law is that there must be two independent braking systems on a bicycle, and both can be on a single wheel.
In theory, you could have a coaster brake and a rear rim brake. You could also have a front drum brake and a front rim brake.
As I say, this could all be incorrect blather on my part.