Crash course in improving front drum brakes: Get in here!

Manco
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Manco
Edited Date/Time 6/4/2016 11:08pm
Long story short, just the other day while ripping down the interstate on a vintage dual sport bike I am prepping for racing I had the unique experience of realizing just how worthless a vintage front drum brake is while I narrowly avoided a three car pile up as I drifted sideways at 65 mph. Pretty much any of my other bikes, dirt, street or otherwise would have come to a stop in the same situation because they all have disks brakes on front. The vintage bike I was riding on the other hand attempted to seriously injure or kill me by refusing to slow down. Luckily cool nerves, lightening reflexes and luck allowed me to avoid rear ending a truck, just miss a SUV I needed to pull out in front of to avoid the catastrophe and go into an asphalt drift at 65mph before throttling back into control and weaving my way out of the mayhem. After that experience a few things are certain to me: 1. Aged OEM disk brakes are horrible. 2. Do not test out a vintage bike project in interstate rush hour traffic no matter how awesome the bike is. 3. Aged OEM disk brakes are horrible.

To improve my front drum brake here are a few things I have put together:

1. New brake cables.

2. New pads.

3. Groove and rough sand the pads.

4. Rough sand the drums.

I am wondering if there is anything else that can be done. Is there a brand of drum brake pads that actually work? Is there a way to increase hand leverage at the lever or at the brake mechanism? Are there modifications that can make a front drum brake worth a crap?'

Any help anyone has please post. Not only will you help folks go stop faster you may save someone's life. Thanks for contributing.

Here are pics of the type of front drum brake I have on my bike for reference:





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Shawbridge Husky 6/3/2016 4:07pm
6/3/2016 4:07pm
Right on love this stuff thanks for posting ! Vintage Brakes.com have LOTS of good info on their site. Relining with current materials and arcing pads with turned drums is the way to go. Race Tech also do drum facing, has to be done with wheel under tension and trued ( with spokes and rim ) If you have access to a big oil field type lathe I guess you could chuck up the wheel true to the axle as well. Is what I'm going to try. There is a Hodaka shop in Cali that has a Dumore bench grinder kind of set up with a carbide burr seems to do a nice job. Wear a mask !
wfoyz250
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wfoyz250 6/3/2016 6:18pm
6/3/2016 6:18pm Edited Date/Time 6/3/2016 6:28pm
Really.......so placing blame on the brakes is what almost killed you? Hmmmmm.......

Looks to me like you may have a yamaha.

This is what you need.
I have them on my bikes. Also don't skimp on cables, pay the extra bucks on OEM Yamaha cables, AS WELL as OEM brake shoes.......YES OEM.

http://www.ebay.com/itm/1982-YZ250-IT-250-Front-Brake-Plate-Yamaha-YZ25…
speedman
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speedman 6/3/2016 6:18pm
6/3/2016 6:18pm
Scroll about 3/4 down the page at Klemm Vintage 350 Bighorn roadrace build for a description of how Klemm optimized the stock Bighorn single-leading-shoe front brake when the AHMRA changed rules to keep Klemm from using a period Kawasaki double-leading-shoe brake. The big thing Klemm discovered that Vintage Brake doesn't discuss is the possibility that the front hub's bearing seats may not be perfectly concentric with and perpendicular to the brake drum; it's easy to assume that the manufacturer lined everything up in there correctly, and even a tiny misalignment hurts potential braking power and is not completely solved by arcing the shoes to the drum carefully.

Other than that, a longer actuating arm at the hub obviously gives you more leverage there, but needs to run smoothly--you have to re-angle the brake cable holder at the hub so that it's pointed straight as straight as possible at the end of the actuating arm; some brakes might even need to have that alignment improved with the stock arm. You're optimizing that so that you're not losing braking force to overcoming friction at the hub end of the brake cable. Likewise, getting the straightest possible run on the cable housing overall on the forks reduces friction loss.

Also, maximum force is applied to the actuating arm when the cable is at 90 degrees to the arm, so brakes are usually set up with an acute angle there at rest, and are pulled toward that optimal right angle. So do the available positions on the splines and the inner cable length give you any leeway to achieve a better pulling angle range? Don't assume that the factory optimized that--they may have been wary of making the front brake too strong for dirt use. And don't assume that the brake arm spline setting and the brake cable are factory stock either.

I have seen someone else suggest that the front brake lever be moved inboard on the bars as far as you are comfortable with, so that you are pulling as close to the outside end of the lever as possible. Again, that's where your maximum mechanical advantage is. I tried it on my bicycle and it works.

Klemm says he got that stock SLS brake working nearly as well in outright power as the period DLS brakes he'd been putting on, and that the SLS brake was more predictable at first application, so it was actually more raceable. Hope there is that much room for improvement in yours & no more close calls--
1
Manco
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Manco 6/3/2016 7:48pm
6/3/2016 7:48pm
wfoyz250 wrote:
Really.......so placing blame on the brakes is what almost killed you? Hmmmmm....... Looks to me like you may have a yamaha. This is what you need...
Really.......so placing blame on the brakes is what almost killed you? Hmmmmm.......

Looks to me like you may have a yamaha.

This is what you need.
I have them on my bikes. Also don't skimp on cables, pay the extra bucks on OEM Yamaha cables, AS WELL as OEM brake shoes.......YES OEM.

http://www.ebay.com/itm/1982-YZ250-IT-250-Front-Brake-Plate-Yamaha-YZ25…
I never blamed the brakes. I just noted how they responded. I was riding in a prudent and safe manner when the flow of traffic simply came to an immediate stop and I made all the right decisions. I wouldn't change a thing about the incident. I lived, learned, and had a blast in the drift.

It is a Yamaha. The organic OEMs make sense as they are stupid grippy. With some disks I do the opposite and run carbon kevlar for less grip smoother response.

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Manco
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Manco 6/3/2016 7:54pm
6/3/2016 7:54pm Edited Date/Time 6/3/2016 7:57pm
speedman wrote:
Scroll about 3/4 down the page at [url=http://www.klemmvintage.com/bighorntech.htm]Klemm Vintage 350 Bighorn roadrace build[/url] for a description of how Klemm optimized the stock Bighorn single-leading-shoe front brake...
Scroll about 3/4 down the page at Klemm Vintage 350 Bighorn roadrace build for a description of how Klemm optimized the stock Bighorn single-leading-shoe front brake when the AHMRA changed rules to keep Klemm from using a period Kawasaki double-leading-shoe brake. The big thing Klemm discovered that Vintage Brake doesn't discuss is the possibility that the front hub's bearing seats may not be perfectly concentric with and perpendicular to the brake drum; it's easy to assume that the manufacturer lined everything up in there correctly, and even a tiny misalignment hurts potential braking power and is not completely solved by arcing the shoes to the drum carefully.

Other than that, a longer actuating arm at the hub obviously gives you more leverage there, but needs to run smoothly--you have to re-angle the brake cable holder at the hub so that it's pointed straight as straight as possible at the end of the actuating arm; some brakes might even need to have that alignment improved with the stock arm. You're optimizing that so that you're not losing braking force to overcoming friction at the hub end of the brake cable. Likewise, getting the straightest possible run on the cable housing overall on the forks reduces friction loss.

Also, maximum force is applied to the actuating arm when the cable is at 90 degrees to the arm, so brakes are usually set up with an acute angle there at rest, and are pulled toward that optimal right angle. So do the available positions on the splines and the inner cable length give you any leeway to achieve a better pulling angle range? Don't assume that the factory optimized that--they may have been wary of making the front brake too strong for dirt use. And don't assume that the brake arm spline setting and the brake cable are factory stock either.

I have seen someone else suggest that the front brake lever be moved inboard on the bars as far as you are comfortable with, so that you are pulling as close to the outside end of the lever as possible. Again, that's where your maximum mechanical advantage is. I tried it on my bicycle and it works.

Klemm says he got that stock SLS brake working nearly as well in outright power as the period DLS brakes he'd been putting on, and that the SLS brake was more predictable at first application, so it was actually more raceable. Hope there is that much room for improvement in yours & no more close calls--
All the lever and leverage stuff really neat. That stuff plus the TT YZ style brake system OEM pads and some friction mods may be the way to go. Thanks for posting good tips everybody.
Cancerman
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Cancerman 6/4/2016 12:53pm
6/4/2016 12:53pm
Speedman has it figured out. The only thing I've done differently, is I use a Motion Pro front brake cable on my 79 Suzuki RM250. It is a huge difference over the OEM cable. I also use shorty levers, moved inward so my finger line up with the lever, and adjust it so I can one finger it. For a drum brake, I can lock it up at times. Good conversation, guys.
newmann
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newmann 6/4/2016 2:35pm
6/4/2016 2:35pm
Careful when selecting new cables from aftermarket mfg's as they are not all created equal. Heck, some from the same mfg aren't created equal...lol.

Now, about the dual leading shoe WFO linked to on ebay. That is an 82 model and the slot for the fork lug is way back at a 90 degree angle. Not going to work. Look for a similar one from 1980-81 YZ465 as the slot will be in the right position. No hole for speedo cable though. Did any it the IT endures have a dual actuated brake???
Zr0man
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Zr0man 6/4/2016 8:02pm
6/4/2016 8:02pm
Did any it the IT endures have a dual actuated brake???

My 83 IT250 has a dual/double leading front brake. Speedo drive on opposite side. Back in the day upgraded my 85 IT200 with the dual leading brake assy from a YZ125 IIRC.
Jim in VA
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Jim in VA 6/4/2016 9:57pm
6/4/2016 9:57pm
speedman wrote:
Scroll about 3/4 down the page at [url=http://www.klemmvintage.com/bighorntech.htm]Klemm Vintage 350 Bighorn roadrace build[/url] for a description of how Klemm optimized the stock Bighorn single-leading-shoe front brake...
Scroll about 3/4 down the page at Klemm Vintage 350 Bighorn roadrace build for a description of how Klemm optimized the stock Bighorn single-leading-shoe front brake when the AHMRA changed rules to keep Klemm from using a period Kawasaki double-leading-shoe brake. The big thing Klemm discovered that Vintage Brake doesn't discuss is the possibility that the front hub's bearing seats may not be perfectly concentric with and perpendicular to the brake drum; it's easy to assume that the manufacturer lined everything up in there correctly, and even a tiny misalignment hurts potential braking power and is not completely solved by arcing the shoes to the drum carefully.

Other than that, a longer actuating arm at the hub obviously gives you more leverage there, but needs to run smoothly--you have to re-angle the brake cable holder at the hub so that it's pointed straight as straight as possible at the end of the actuating arm; some brakes might even need to have that alignment improved with the stock arm. You're optimizing that so that you're not losing braking force to overcoming friction at the hub end of the brake cable. Likewise, getting the straightest possible run on the cable housing overall on the forks reduces friction loss.

Also, maximum force is applied to the actuating arm when the cable is at 90 degrees to the arm, so brakes are usually set up with an acute angle there at rest, and are pulled toward that optimal right angle. So do the available positions on the splines and the inner cable length give you any leeway to achieve a better pulling angle range? Don't assume that the factory optimized that--they may have been wary of making the front brake too strong for dirt use. And don't assume that the brake arm spline setting and the brake cable are factory stock either.

I have seen someone else suggest that the front brake lever be moved inboard on the bars as far as you are comfortable with, so that you are pulling as close to the outside end of the lever as possible. Again, that's where your maximum mechanical advantage is. I tried it on my bicycle and it works.

Klemm says he got that stock SLS brake working nearly as well in outright power as the period DLS brakes he'd been putting on, and that the SLS brake was more predictable at first application, so it was actually more raceable. Hope there is that much room for improvement in yours & no more close calls--
Very good points about highest leverage at 90 degrees (pulling point farthest from center of rotation) and cable routing/friction losses. I haven't had drum brakes in many many years, but as a kid, used a thin wipe of anti seize lubricant on the pin and the flats of the actuation shaft (where they contact the shoes to spread them) to reduce friction there too. It seemed to help as it is a great high pressure lubricant. Just a VERY thin wipe is all I ever used, and it never seemed to contaminate any of the other parts you DON'T want slippery... Just a thought. If you do try it, be sure not to get it anywhere else (friction material on shoes or drum) due to its great friction reducing properties.

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