Increasing Drum brake performance

Is there a way to increase drum brake performance? Does slotting the pads work? Is there a way to roughen the drum?

I can do skids with the drum brakes on my si but I have to go flintstone with the puchs what gives?

Re: Increasing Drum brake performance

King Drunky JCams /

Colin, I can second the Si brakes. My friend's Si will lock up the back tire no problemo.

As for getting better stopping power on the puch brakes... try this... hopefully I can explain it well.

Take the brake shoes completely off of the brake plate. On the little pivoting piece that actually turns and presses the brake shoes outward, wrap a strip of steel around it. The steel strip should be the width of the pivoting thing and just long enough to meet end to end when wrapped around one time.

Think of it as wrapping a stick of gum around it until the ends meet.

This extra material between the pivoting piece and the brake shoes causes the shoes to stick out further and with more force when you squeeze the brake lever - and you'll stop harder.

Kinda tricky to explain, but I've done on several bikes and it seems to help quite a bit. Especially if the brake pads are a bit on the thin/worn side...

Good luck.

J

Re: Increasing Drum brake performance

Recently put NOS cables on my moby and sanded the rear pads, and the brakes are pretty good. Can't quite lock them up though.

Ideally tuned brakes which only have to move a tiny bit would allow a longer brake arm for increased leverage. But then again these are moped brakes so...

Would like to hear more input on this one.

Re: Increasing Drum brake performance

campbell that sounds like an interesting idea. gonna try it.

one thing you might want to consider, if you feel like doing a custom jobby, is to study the brake setup on most sachs bikes... theyve got the "pedal backwards" rear brakes that will lock up the rear wheel in no time. im not sure exactly how their setup works, i believe it incorporates some kind of claw clutch, because you can still pedal forwards but not backwards.

i plan on doing this, but not necessarily using the claw clutch idea. a little over complicated. Im thinking instead of just getting some good fat motorcycle brake cable, and rigging up something on my moby so that pedaling backwards will pull the cable. shouldn't be too difficult, i dont think, although i will probably loose fullrotation of my pedals (not that i care, cause i push start and dont have a pedal chain anyways).

this probably isnt the idea youre looking for though. just saying that you can always crank out a lot more power with your legs than your hands.

Re: Increasing Drum brake performance

Hey justin I was thinking of this also. What guage steel did you try? I was thinking of chopping up some metal blinds to see what happens.

Re: Increasing Drum brake performance

J Campbell, that little rotating piece is called a "cam." Increasing the size, or the ramping of a brake cam will change how powerfully, and how quickly your brakes engage, respectively.

So far, that's a good plan, but putting an unsecured piece of metal inside your brake drums is a Very Bad Idea. Even if you shim your brake cam to get better performance out of it (and somehow avoid over-shimming so as not to burst or crack your hub) you can't just leave that shim there - you need to do _something_ to secure it in place.

The perfect implementation of your plan would be to remove the cam, weld on some extra metal, and then file it down until it is exactly the right shape to engage the shoes on the inside of the hub shell.

At the very least, use some glue, or a tapped-and-faced hole, or a flattened-thimble-like covering that bolts to the flat side of the cam, or...

+++

Increasing the length of the lever arm on the brake hub itself will make your hand lever move more (you'll have to pull it farther, and have less adjustment room) to make your brake shoes move a shorter distance more powerfully.

Colin, if your brakes are in good tune, and you haul on the hand lever without bottoming out at the handle bar this would give you more braking power (and probably better braking response).

Brake drum lever arm failures are among the primary reasons old motorbikes were recalled. I'd suggest finding a bigger lever arm, or building an entirely new, larger lever arm (basically, don't try bolting on an extension to the existing arm).

+++

Do we just assume that Colin knows to de-glaze the insides of his hubs? Colin, do you know to de-glaze the inside of your hubs?

As brake shoes wear, they leave a burnt deposit on the inside of the hub shell (they shouldn't, but they do). Brake cleaner gets this off, as does sandpaper. You are not supposed to use sandpaper for some reason (asbestos? Brake surface scratches? I don't remember).

+++

Doesn't the Sachs use a coaster brake? Coaster brakes have a sprocket with a threaded cone. When the sprocket is rotated backwards - when you pedal backwards - the cone "unscrews" from a pair of brake shoes inside the hub - in effect, the sprocket replaces the brake cam as the actuating method.

I think that this means that you can roll a Sachs with a coaster brake backwards without the pedals turning. I am not sure how useful that would be.

Re: Increasing Drum brake performance

I figure you know this and you want to lock up just so you can do a sweet skid stop in front of some hot babes to impress them, but locking up a tire reduces the tires frictional force, reducing it's stopping ability. for performance reasons, I'd adjust the brakes, especially the back one, so that you're about to lock up at full braking force. the point where a tire is about to lock up, but doesn't, is where it brakes the best. "Optimal Braking."

But again, I'm not trying to impress with info you don't know, I just believe in covering all the bases. Skid Mark=Hot Chick On the Back Of The 'Ped!

Re: Increasing Drum brake performance

I'm definitely going for skidmarks with this one...

Re: Increasing Drum brake performance

Locking up a a rear brake in a real panic stop isn't so cool... I will admit that it's pretty fun to do when you are ready for it. 180 skids ftw.

Re: Increasing Drum brake performance

went snowpedding the other day in 2 inches of snow with my bald tires and did 180s galore. that brake is the most unique thing about sachs bikes and its what makes em so fun. try it on a g3, thats excellent.

thats why i think itd be so great to get a similar setup on another bike.

Re: Increasing Drum brake performance

i want to hear your techniques on de-glazing the hub and the pads. i use sandpaper and sand against the direction of the pads. i do this top both the hub and the shoes. sometimes this works great, and sometimes it seems like it doesn't do any thing.

what grit should i be usiing? superfine? WHAT WORKS EVERYTIME??

BTW locking your rear wheel IS THE GOAL, it may reduce your ability to stop as efficiently as possible, but then you know that you brakes are working ass efficiently as possible, and a controlled non-skidding brake can be made at any time.

if you can't lock up your wheel, then your brakes aren't good enough.

Re: Increasing Drum brake performance

heather nailed it. locked up tires means good enough brakes, assuming a proper tire.

plus, skids are fuckin awesome when you mean to do them.

there's a specific type of sandpaper you should and shouldnt use. either silicon dioxide or aluminum oxide, i think. not very useful info cause i dont know which is good and which aint.... anyone refresh me?

Re: Increasing Drum brake performance

what is emery cloth made from?

what is the paper with black sand made from?

hmmm... now we are getting somewhere!!!!

Re: Increasing Drum brake performance

King Drunky JCams /

"So far, that’s a good plan, but putting an unsecured piece of metal inside your brake drums is a Very Bad Idea."

Yes.

However, they are certainly not unsecured... I wrapped the steel strip so that the ends fall on the flat spot of the cam. That spot is under constant pressure from the brake pad and I've had no problems with this setup for over 1000 miles on my Hobbit alone. No sign of wear or loosening of the strips at all.

Colin, not sure about the gauge... I'm thinking 16 or 18. what ever I had lying around at the time.

In short, it works great and as a plus is super cheap.

Win-Win.

Re: Increasing Drum brake performance

don't get an fa 50. new brake shoes no luck, tighten it yeah it works really nice but it rubs so it slows down top speed and acceleration. un turn till it doesn't rub, better than in the beginning ,still sucks but better. final solution wear an old pair of shoes and flinstone it. works quite well except when you need to run on ice , no grip in shoes :(

Re: Increasing Drum brake performance

One of the dutch tuners made a foot brake for a puch, but you would have to remove the pedals. That seems like the only way to get enough leverage.

Re: Increasing Drum brake performance

Downhill Harvey (OFMC) /

I did what Silverfox says in this thread, https://www.mopedarmy.com/forums/discuss/6/120420/120420/ , damn link better work.

Re: Increasing Drum brake performance

Get some cable lube and use it. Also grease all pivots etc. Friction in the mechanical systems wreck efficiency.

Re: Increasing Drum brake performance

Using bicycle cable housings that are lined is a real plus. Exige brand brake shoes are nice. When I sand the drum and apply the brakes it puts metalic bits in the brake shoes reducing their effectiveness. Taking them apart and sanding the metal out of the shoes and you are good. I am lazy so I don't sand my drums anymore. But those bike cable housings really work wonders. Credit to Naz for bringing it to my attention. You can try to soak the grease out of old shoes but the shit it usually cooked in there preety good.

Re: Increasing Drum brake performance

yeah, jagwire brand cables use some crazy longitudnal wire shit that is awesome. i use them for throttle.

Re: Increasing Drum brake performance

use aluminum oxide paper. silica is slippery.

Re: Increasing Drum brake performance

"When I sand the drum and apply the brakes it puts metalic bits in the brake shoes reducing their effectiveness. Taking them apart and sanding the metal out of the shoes and you are good."

Steve, do you mean that after you sand the insides of your brake drums, you have to use your brakes a few times and then clean them out?

I don't think I've ever done this intentionally, but it sounds like a good idea.

+++

Campbell, yes, that friction fit holding your metal strip in will be pretty strong. Also, the pressure on the cam won't stop unless the springs in your brakes fail, at which point you've got all kinds of problems anyway.

Still, while I like the simplicity of this idea, I'm still wondering how you could tweak it to make it a near-permanent modification.

What if you used a thinner strip of metal that wrapped around more than once? Then, you could coat the strip of metal with flux, and use a torch to braze it all together with some solder (or, ideally, with some brass).

In case I ever have to do this (and I probably will - I've got a whole mess of random drum brakes for bicycles, mopeds, and motorbikes), what kind of steel are you using as a wrap? Standard-gauge sheet metal thickness, or cheap cookie-tin thickness?

If it's the former, then the brazing idea might work well with the latter.

Re: Increasing Drum brake performance

bump

Re: Increasing Drum brake performance

A little tig weld would make that metal strap permenant. You could weld it to itself, so you could easily cut it off later, or you could weld right to the cam.

Re: Increasing Drum brake performance

Yes James thats what I say. The local vintage moto boys around here have a guy that relines your shoes with any hard to soft material you choose. I should try him

Re: Increasing Drum brake performance

King Drunky JCams /

Standard guage sheet steel.

I think it's 18ga. that I used on my brake setups...

As for a couple wraps and then soldered, that would probably work just fine. You then at least it would be super secure...

Re: Increasing Drum brake performance

Things that have worked for me:

Thicker cable from a motorcycle

moving the attachment point up on the brake arm, making a shorter brake arm.

new shoes

The sachs rear brake isn't a true coaster brake. It's a normal lever pulled brake, that is activated by pedaling backwards. It's leverage- a really short brake arm, and all the weight you can put on a pedal arm makes it work really well.

Re: Increasing Drum brake performance

why would you want a shorter brake arm??? isn't that less leverage????

Re: Increasing Drum brake performance

Less leverage, but is that really where you need the leverage? Think less cable movement.

When was the last time you were like "Oh damn this brake lever is really hard to pull."

Re: Increasing Drum brake performance

That would make the brake mush less responsive. I don't know if that's a bad thing.

Responsiveness isn't effectiveness, it's just the degree to which you can control the braking force. A shorter lever on the brake itself would make the hand lever more like an on/off switch.

That does seem like an odd thing to do, but I can't knock it. You say that this worked out for you Mike? Was it possible your hand lever didn't match the brake hub?

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