Front Drum Brake - Very Poor Performance (Even After Cleaning and Adjusting) - Cable?

[technostructural]

Hello All,

I have a front drum brake on my GS450. I believe it is from an older bike, because mine is an 83. Exactly how my bike came to have a drum brake, I have no idea, but the fact is -- I've got one now.

I've owned the bike for a few years, and I've always noticed that the front brake (in comparison to the rear drum) has terrible stopping power. I've ridden other bikes with drum brakes, and this one is particularly bad. After some fairly scary experiences, I figured it would be time to open it up and see what the issue was.

Turns out, that there doesn't appear to be much wrong with it. The shoes had plenty of life, no sign of oil contamination. I cleaned things up with brake clean, re-lubed the cams (lightly) with some high temperature lubricant and put it all back together. I attached the cable, and yep, just about the same terribleness. I can grab a fistful of front brake and still push the bike forward.

What is odd is that, with the cable off, if I just grab the arm on the drum and pull it tight, the brake seems to stop quite well. All of this is to say that it seems as if the cable and/or brake lever is somehow reducing the performance of the brake. Is this possible? I know that cables can and do stretch somewhat, but it feels almost as if the braking action is elastic. I can apply the brake with the lever, and squeeze the lever in more than half way. The stopping power gets slightly stronger as I do so, but not significantly.

What is the conventional wisdom on this? Just swap out the cable for a new one?

Thanks.

 

[Sandy]

I think your bike came with the drum brake stock. It's what is called a twin leading shoe brake and has a rod on the outside of the brake hub that if not adjusted properly will give poor performance. It's been a long time since I've adjusted one but IIRC the rod should be adjusted so the leading edge or forward edge of both brake pads in relation to wheel rotation should contact the drum slightly before the trailing edge of the brake. You should find the proper adjustment procedure in your shop manual.

 

[Rijko]

usually the issue is not with the brake lever or cable.

If someone sits on the rear of the bike to lift the front wheel, you spin the
wheel, i bet it stops at the slightest touch of the brake lever.

If you tie a rope on the arm of the drum and have someone pull it ..
you cannot push the bike forward ?

Usually the old brake shoes are glazed and stop working well.
Sometimes this can be remedied by sanding the brake shoes down a bit,
but chances are bigger new ones solve the issue.

Or the drum has an issue, it's cracked and gives way under force,
has so much wear that the inner diameter is so large the brake shoes
can't expand enough to get a good hold, something like that.

 

[Rijko]

i'm slow typing ... Sandy's post was not visible when i started my reply...
Sandy is probably right on the brake actuator arm not properly adjusted.

Forgot about that issue, it's been a long time for me too.
How about a picture of the front brake drum with cable installed ?

 

[technostructural]

i'm slow typing ... Sandy's post was not visible when i started my reply...
Sandy is probably right on the brake actuator arm not properly adjusted.

Forgot about that issue, it's been a long time for me too.
How about a picture of the front brake drum with cable installed ?

I'm at work right now, so I don't have easy access to photos. I will snap one and post it up here as soon as possible.

When I took the assembly apart, I did give it all a good sanding. The drum did not appear to be cracked or damaged. I did not measure surfaces with my digital calipers, but I can say that everything looked like it had quite a bit of life left in it. It seems like the timing of the shoes hitting hte drum is likely the culprit. If they were out of sync (per se), I imagine that would give the illusion of that spongy or elastic feel in the brake, because if one shoe touches down first, it would leave a sort of "play" in the other. So the brake would most likely only ever be half actuated.

Sounds like a plausible explanation. I will dig into this a bit more and get back to y'all. Thanks for the pointers.

 

[Guest]

Even adjusted perfectly, I've never been able to get a Suzuki twin leading shoe to get what I would call safe stopping power. That's not to say it can't be done; I've run some Italian TLS brakes that were respectably powerful but the bikes were way lighter and the shoe compounds were special and you had to get a good setup and maintain it. I could never get a Suzuki brake to that standard, leverage ratio being one problem. It's as if they were afraid you might inadvertently lock the front wheel on sand and sabotaged accordingly.

Even the original GS disc brakes with the round pucks were rather lame, but the original on a 450T is a dandy brake. Why it took until the '80s to get it right is a mystery, but I'd recommend going to what was on there stock in the first place. The cast wheels are far easier to find than the spoke version but there are spoke wheels from other models and years that will fit, if you want to stick with spokes. I can sympathize with that.

Much as I used to enjoy fiddling with squeezing the last bit of retardation out of drum brakes, the disc is just another and better world. Totally boring, and totally linear and dependable.

 

[Guest]

As others have said, the 2LS brake actuator arms needs to be properly adjusted.


Its also really important that the brake be properly lubricated.
Most important and usually completely neglected is the brake cams. Typically you end with metal to metal contact between the cams & the brake panel, and then the brakes work like crap.


The brake panel needs to be disassembled. Use high pressure grease in the holes where the cams go thru the brake panel. A smidgen of grease on the shoe pivot points help a bit too.
Clean up any extra grease & get absolutely none on the shoes.
I use CRC Sta-Lube Sta-Plex extreme pressure red grease. It was recommended some time ago by the Vintage Brake people.


Also lube the cable. Use a smidgen of grease on the lever pivot & the cable end.


I have some links for drum brake service & will provide them later.

 

[Cipher]

On old dirt bikes front drums started getting weaker as the cable failed strand by strand,
might be down to a few strands inside the housing. Is a new cable a cheap thing to check?

 

[Tom R]

Agreed on the cable as they're cheap. I had terrible brake on my cl175, I broke the glaze on the pads and drum; then adjusted the shoes per factory manual - also, loosen the axle bolt, and torque it back down as your squeezing the brake to help center the hub - was night and day the difference it made.
Look up vintage brake, he has a ton of info on his site.

 

[Guest]

As others have said, the 2LS brake actuator arms needs to be properly adjusted.


Its also really important that the brake be properly lubricated.
Most important and usually completely neglected is the brake cams. Typically you end with metal to metal contact between the cams & the brake panel, and then the brakes work like crap.


The brake panel needs to be disassembled. Use high pressure grease in the holes where the cams go thru the brake panel. A smidgen of grease on the shoe pivot points help a bit too.
Clean up any extra grease & get absolutely none on the shoes.
I use CRC Sta-Lube Sta-Plex extreme pressure red grease. It was recommended some time ago by the Vintage Brake people.


Also lube the cable. Use a smidgen of grease on the lever pivot & the cable end.


I have some links for drum brake service & will provide them later.

https://www.louis.eu/rund-ums-motorrad/schraubertipps/bremsbacken

http://www.dansmc.com/drumbrakes.htm

http://www.cyclepedia.com/manuals/online/free/brakes/drum-brakes/

I have a better reference but didn't find the link.

 

[chuck hahn]

Deglaze the drum too. Get some 400 or 600 and sand the glazed up crud off it.