So Im going through my collection of old Rod and Customs and find this article on Drilled Drum Brakes. Seems by drilling holes in them just like disc brakes, they totally change for the better.
The company CH Topping, will drill your drums, you can find them on line, they're in Long Beach. If you go to their website, they have a reprint from the 2001 article you can read.
So what does drilling drums do for you? Releases gasses and heat, that make drum brakes fad. Gets rid of water, that if you have ever driven a drum car in water is like try to stop the car, by dragging your foot out the door.
The article hints toward fuel economy. Drums are 3 times lighter than discs. Calipers are 4 times heavier than wheel cylinders, and the brake surface area of a drum brake shoe is 6 times larger than a disc pad.
So what does the future hold? Light weight efficient drums for economy cars. The manufacturing draw back? Disks on the assembly line are quick to install, drums are inticate and take longer to install. Benefit, drums are light weight. So if you have an older drum car, save the money by not having to do a disk conversion.
I believe what Benfrogg is refering to is what they used to call "Self Energizing" brakes. A VW bug has 2 wheel cylinders pushing out, using both shoes, by using 1 wheel cylinder, as in American brakes, the first shoe grabs and pushed the second shoe harder, requiring less braking force. That's how the 2 shoe, single cylinder braking system was explained to me.
The trick is drilling the drum, not the brake shoes. I'd like to try the trick, I just don't have anything with drums right now, but I have been looking at 50's, 60's rods, that I plan to do a V6 engine conversion in. I think I'll do a post on Eco-Hot Rodding.
My rears are drums - small and pretty heavy because they are thick. The heat surface of a drum is on the outside too so that helps radiate the heat. I think the main problem with drums however is that they trap a lot of heat inside and cause a lot of cylinder heating where the calipers on a disk get some air cooling. Drums can warp and crack just as well as a disk brake but is all depends upon the quality of the materials used.
One thing for sure is that checking a disk brake for wear is a lot easier than a drum brake.
I think half the listed benefits are vaporware. Drums aren't likely to be three times lighter than disks, not when drums have metal taking up close to the same area as disks, then wrapping all the way around the shoes for a couple more inches, adding a lot more metal mass and weight. Even figuring that calipers add weight to disk brake systems, drums have larger and heavier shoes and added springs and star adjusters. I suspect any weight difference is closer to a wash than a 3:1 ratio.
Ditto for drums supposedly having six times the braking area of disks. That probably assumes brakes of equal diameter, which isn't true in the real world. Drums are typically smaller, maybe 7" in diameter v. 11" disks. Stop twice, and drum heat will cause enough fading to decrease their effectiveness to 1/4 or less what they originally did.
i've driven many different types of large construction/delivery vehicles and have NEVER realized a loss of stopping capability after multiple stops. these vehicles, as you know, are 4 wheel drum equipped.
Most of the issues with drum brakes are a wash if you design them correctly. only poorly sized drums with cheap friction material fade in a few stops.
The only argument that I've heard explained convincingly is shedding dirt/water and heat. Dirt (including brake dust) or water can get temporarily trapped in the drum whereas disks will usually clean themselves in a few revolutions. heat shedding ability is a trade-off: vented disks shed heat faster but absorb less. drums take longer to overheat but once they're hot, they don't lose it as fast.
The reason they're so widespread on new cars are
1. safety because of the self-cleaning aspects.
2. heat shedding: Usually cars aren't braked long enough to do damage, when they are you get warped rotors
3. (and most importantly with 100k mile warranties and long maintenance intervals) little or no maintenance and very few moving parts. Doing drums is like building a Rube Goldberg project on some cars and there are many ways of doing it. Disks come in far fewer varieties with less variation where there is any not to mention fewer pieces to assemble.
1991 Toyota Pickup 22R-E 2.4 I4/5 speed
1990 Toyota Cressida 7M-GE 3.0 I6/5-speed manual
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"You don't get to judge me for how I fix what you break"
Also if i remember right disks activate quicker than drums. That and they are a heck of alot easier to assemble.
Yea disks dry off a hell of alot quicker than drums but most cars have drum rears still because theres no point in worryign about that as the rear only does 30% of your stopping anyways. (hence why thier usually so small too)
The previous mentioned advantages/disadvantages are all somewhat valid BUT the drilled rotors and drums argument i feel.
yes u are making vent holes to shed away dirt but lets REALLY stop and think: If you drill out rotors or drums you are decreasing your stopping power because you just removed some friction surface. (think of it as racing slicks VS M+S tires on a dry track) Releasing heat? maybe but your gonna create more with less metal to help it evenly dissapate.
if it were so much better why hasnt any car manufacturer since the model T drilled any rotors or drums?(yea theres prolly a few oddball ones but not any normal class cars) Especially on cars / trucks that have long stopping distances or common brake fade problems.