Why does my front drum brake suck so bad?

[Flugtechnik]

The title pretty much says it all. My front drum brake sucks. I tried adjusting it as the manual says but to no avail. Does anybody have any pointers on how to adjust these things so they actually work, besides replacing it with a disc?

The lowdown:
1972 CL450
Double leading shoe
Newish shoes
Everything looks fine inside the brake (drum is smooth)
Cable action is smooth.

 

[DrJ]

I find stock cable housings are a bit compressible. The force your hand applies to the brake lever is absorbed into the casing rather than being used to increase pressure on the drum by the shoes. Maybe order a custom cable with non-compressible casing from here:

http://www.motionpro.com/custom/index.php

 

[Swagger]

Also make sure all the radii in your cable routing are as large as possible. Tight bends in a cable add stick-tion which can really f-up your lever feel as well as the action. You might need to deglaze the liner in your hub with a little 400grit w/d. Are the shoes matched to the diameter of the hub? As the liner wears it's going to enlarge in diameter, as such if you're shoes are in spec for a new hub (they all are) then you're missing out on contact area. Even .001" will make a huge difference on the contact patch of the shoes. For an example of what I'm talking about, take a CD (this will be the diam. of your hub, and say an old chain lube can (this will be the diam. of the shoes......drastic I know but it'll show you what i mean). Set the can on the cd so that the edges line up at one point. That's an exaggerated example of what you're dealing with, you want the diameters to be very close but with enough room to allow the hub to spin freely.

To get the best possible contact patch your shoes will be mounted to the backplate and expanded to the point that they'd make contact with the hub, then the entire assembly is chucked into a lathe and the surfaces of the shoes cut to suit the working diameter of the hub. Now when you grab a handful of lever the whole surface of the shoe will contact rather than just a portion of the arc.
Result....much better brakes.

 

[Tim]

Everything you want to know and need for old drum brakes:

http://www.vintagebrake.com/index.html

Drum brakes suck because they're drum brakes for the most part, but with work they can be very effective.

 

[swan]

There is nothing wrong with drum brakes and I prefer them over disc. Take the time to set them up correctly and they work well.

Check you pads to ensure the are thick enough, not oily or greasy. Deglaze them with sandpaper and clean with acetone. Clean your drum with acetone. Ensure the are seating properly and your drum liner is clean and true. Ensure you actuating arm is set up correctly to give maximum shoe contact. Grease your cables and make sure there are routed correctly.

Read more on drum brakes and modification here: http://victorylibrary.com/brit/2LS-table.htm

 

[Flugtechnik]

Thanks for all the links guys. It looks like I have a good amount of info to absorb. I think part of it may be what DrJ described as I can see the cable housing moving a good bit as I squeeze the brake. I think the rest is all in the adjustment or cleaning of the shoes. My back brake seems to work better than the front and it isn't a DLS!