drum vs disc for front brake?
 

I already have the right length spokes to build the wheel with a drum brake, but since I'm going to need a new fork (unrelated reason) I'm wondering if I should go with a disc brake instead.

What do you guys think? If the disc brake setup isn't going to be lighter then I think I'll probably just stick with the drum.

Disc definitely won't be lighter, as there's usually more substance to the fork, and the rotor and caliper weigh more. Will definitely supply more stopping power, so it's really a question of whether it's an all-weather bike or loaded enough to warrant it as to whether it adds value for you.

Remember we're comparing drum to disc brake here. Not disc to rim brake. Are you sure the rotor and caliper will weigh more than a drum brake?

Only comparison I can remember was a Shimano Dynohub w/ disc vs Sturmey Dynohub w/ drum and they weighed about the same.

I weighed the Sturmey alloy 70mm frt drum brake hubs, the no dyno version weighs 760gm, 1220gms with the dyno. It's probably heavier than a disc, but cooler!

For shear stopping power would not a disk brake be the clear choice? I have a drum front brake SA and it not as good as a good V-brake under dry conditions.

Someone reported that an Alfine dynohub w/ BB7 mechanical disc rotor and caliper weighs a little under 2kg. Maybe the integrated drum/dynamo in the Sturmey saves weight by, for example, allowing a stiffer hub shell to perform double duty or something, but given their appearances double duty seems unlikely:
http://www.sturmey-archer.com/userfi...small/X-FD.jpghttp://www.sturmey-archer.com/userfi...mall/X-FDD.jpg

Obviously the only way to settle this for the brake hubs w/o dynamos is to actually compare the weights, but considering the facts above I think it most likely that the drum brake hub is lighter than a comparable disc brake+hub. Especially if one opts to use a lighter fork with the drum brake.

Yeah, but stopping power is only half the problem; The other half is reliability and robustness. My biggest fear is discovering my brakes were tampered with or in need of adjustment as I try to stop myself from careening in front of a mac truck. For me it's way more important that I stop reasonably fast every time than that I stop instantly 99% of the time and not at all the other 1% of the time. Besides, I'm a bit skeptical of those who criticize the stopping power of drum brakes because there seems to be a bit of confusion/misinformation about how to properly adjust them with many folks "in-the-know" claiming they are just as good as V-brakes in the dry.


In any case I've decided to go with the drum brake for the following reasons:
1. I have the spokes already cut to length.
2. I'm a light rider and disc forks are almost certainly overbuilt for me. With a drum brake I can pick a fork appropriate to my weight.
3. I'll be running 23c tires and, let's face it, all the stopping power in the world isn't going to overcome insufficient tire traction.
4. The drum setup is probably lighter and cheaper.
5. The drum brake is lower maintenance and safer against booby traps/vandalism.

No no, under 1 kg.

Alfine appr. 570 g (without quick-release)
BB7 caliper 155 g
160mm. rotor 105g
Front adapter 15g

I just bought a disc fork to make one of my 700c commuters into frt dyno/disc, it weighs 1200gm, the non-disc fork it's replacing is 900gm. So the disc set up is 570+155+105+15+1200 =2045gm and the Sturmey dyno/drum is 1220+ 900 = 2120gms.

My SA weight included axle nuts, the Alfine weight didn't include a QR, that's another 60gm.

Looks the the SA is 15gms heavier....

Here's some IGH/drum and dyno/drum porn for your viewing pleasure:

What's the flange height on the Alfine dynohub? If it's shorter than the difference in spoke lengths could make the SA setup lighter. Also what about the pads? I bet it's not included in the caliper weight. :)
I know I'm splitting hairs, but 15 grams is what split hairs weigh.

Although there is a big difference in weight between your forks. There's only 100g difference between the disc and nondisc Nashbar carbon forks.

Drool. Can't beat the look of the chrome fork with the fat chrome hub.


Decisions decisions...

[QUOTE=chucky;101371373. I'll be running 23c tires and, let's face it, all the stopping power in the world isn't going to overcome insufficient tire traction.[/QUOTE]

One misconception is that the width of the tire contributes the stopping power. The stopping force is weight multiplied by the coefficient of friction of the tire, so the tire width does not contribute.

Schwinn Sports Tourer/Super Sport vs Dimension Cyclocross disc fork for 700c wheels. Charcoal forks is against my religion :)

IMHO, the main point is, it's close. My freaking work backpack with laptop is almost 20lbs, what's a few oz one way or another?

Just received an SRAM 730 QR disc/3.0W dyno, it weighs 620gm with QR.

I believe the misconception is yours. Coefficient of friction is an extremely complex quantity which is affected by tire width among other things.

Another assumption is that the tire remains in full contact with the road, the validity of which varies with tire width and pressure among other things. The point is that due to the texture of the road surface, the suspensive properties of pneumatics, and the well known aberrant behavior of rubber the coefficient of friction is simply not a constant property of the two materials as it is in some simpler scenarios (or equivalently we can simply say we're not dealing with "friction" but rather "traction"). Heck, according to Sheldon Brown it's even affected by the posture of the rider.

As I said it boils down to the fact that the coefficient of friction is an extremely complex quantity the determination of which in general is a science in itself (and perhaps one of the most important ones of the modern age at that). So I don't think this is going to be settled in another thread either.

Good choice with the drum brakes. The only situation in which you'll get improved performance on level terrain with disc brakes is to go hydraulic. On hilly terrain, that's another story altogether, as drum brakes will fade when hot. (think long mountain descents, not just coming down a hill in the city)

Overall, assuming you use a proper 4-finger brake lever designed for cantilever brakes, and keep your brake housing as tightly bound as possible, I'm sure you'll find drum brake performance to be the equal of any caliper brake in the dry and in another league in the wet.

This is one of those tired old urban myths made up by bike-journalists/industry ho's to sell overpriced brake systems to un-suspecting riders. How weak do one's hands need to be for this fable to come true?

I plan on using a caliper brake in the rear. I think it an ideal complement to a drum for long descents.

Perfect, the silly fool that's never figured out a wheel doesn't stand on it's spokes, is an advocate of hydros....I'll rest my case....

BTW, I engaged Josbt in the old Palo Alto Bike Shop in the mid 80's. It's clear Josbt doesn't want to debate the "standing on a spoke theory" with anyone that has even an undergrad engineering degree...I fear Josbt had a little trouble passing Statics :p

Even the cheap as hell Hayes mechanical discs on my Buzz don't drag, and they're approximately 2.5 million times easier to adjust than the damned cantilevers on my RB-T.

I'm curious how old that Brandt article is. If it's from the '90s it may have been correct at the time,but I have zero probs with any of my brakes dragging,or having to apply excessive force to stop quickly.