When I got my YZ I realized just how pitiful my vintage drum brakes were, so I replaced all my brake shoes, deglazed the drums, cleaned everything up really well - and they worked even worse for about 3 weeks or so, until they returned to their normal filthy/glazed condition.
So I started looking around for alternatives to the OEM shoes, which apparently are designed for long life and low cost, not maximum braking power.I forget where I heard about Velvet Touch aftermarket linings, but after searching the Web a little I realized that the original Velvet Touch lining material is discontinued and pretty much unavailable - but there are still plenty of friction materials out there.
Here's a picture of OEM (left) and relined (right) '74 CR125M brake shoes. Notice how much metal is in the aftermarket lining:
I've been using these linings for about 2 months now, and they definitely have more stopping power than the stock shoes. They work best when slightly warm, and I haven't really noticed any fade when using them normally, both on and off road. I can now almost lock my front wheel at low speed on dirt, whereas I couldn't even come close before (the CR125M brakes are super-wimpy 4"-diameter single-leading-shoe pieces of crap).
These linings turned my poor brakes into OK (for drum) brakes. I think they would turn OK brakes into fairly good ones. I'm putting an '83 IT250 double-leading-shoe front brake on the CR, and it will be interesting to see what improvement they'll make on this already-good brake setup.
I learned yesterday that this lining is used on holding brakes for large industrial machinery (conveyors, cranes, etc.) and was designed for maximum static friction. There may well be even more aggressive lining materials out there, although at some point drum wear might become a factor.
Pretty much any friction materials/brake relining shop can do this for you, and you might luck out and find someone who will provide info and options on what material will work best for you - maybe even a fellow biker. As mentioned in the title, these alternate lining materials can also be used on clutch plates, although that's a lot more work than a set of brake shoes.
Here's a partial list of factors that can affect drum brake performance:
Wheel bearing slop (axial, radial, angular)
Actuator arm slop, lubrication, leverage, flex
Brake shoe pivot slop & lubrication
Pedal/lever flex, pivot slop, lubrication, leverage
Cable stretch & lubrication
Drum eccentricity, material, surface flatness & condition
Drum/shoe cooling & waterproofing
Brake lining material
In other words, they only work their best when new.
I took my YZ in the woods around here once, but as soon as that brand-new disk pranged off a rock I cut my losses and went home for my other bike. Hopefully at some point I'll get these drums working acceptably well.
I posted this over at ThumperTalk, but I figured somebody might find it useful here as well.
Ray