GV27

Yeah, rim brakes are in the same category as steel frames, panniers, freewheels and gears - bad ideas that never did work.

Yawn.

Sixty Fiver

Mechanical disc brakes are as easy to install and set up as v-brakes and do provide the best all round stopping power you can get.

The benefit also includes the fact you will save your rims and in some places like Portland and Vancouver disc brakes will save you the cost of having to replace rims at a freakishly high rate.

My mountain bike has a front disc and a rear V... the disc provides all the stopping power I need under most conditions and the rear V will provide more than enough power to lock up the rear wheel.

The rest of my bikes run rim brakes and they serve me well in the conditions I ride in.

CliftonGK1

I don't have discs on my commuter/distance bike, but I'll put them on my hauler build when I spec out my next bike, because I don't feel like rebuilding wheels as I grind through pairs of rims on a loaded bike in wet, gritty conditions.

I went for a soggy 36 miler with keithm0 yesterday, and really got to put my new cantis to the test. Tektro CR720s: Old school, wide profile, but they use V-brake cartridge pads. They're rim-crushingly strong and don't have the typical old-school canti problem of having to fart around with pad adjustments every time you replace a pair. I've got them toed-in properly so they don't squeal (even when wet), and when these pads wear through I pop out the pins and slide in a new $5.00 pair.

cyccommute 

Non sequitur: Latin for "it does not follow."

If I sent you a set of brake pads from an Avid Juicy system, would that mean that one is a disk and another isn't? They aren't interchangeable but both are still disk systems. Both use a caliper to squeeze a friction pad against a rotating disk. Oddly, that is just the same as a rim brake. A caliper squeezing a friction pad against a rotating disk. The fact that the pads and calipers aren't interchangeable with some other brake system doesn't mean that it's not the same principle nor that it isn't the same kind of brake.

I have not said anything about the effectiveness of either hub mounted disk brakes or rim brakes. However, if you can skid the rear wheel on either, how much more effective do you need the brake to be? A disk may allow you to apply more clamping force to the disk than you can with a rim brake (still a disk brake) but all that does is make it easier to skid the rear tire. The effective braking limit is still the amount of force you can apply to the front brake before stopping its rotation and throwing the rider over the handlebars.

BarracksSi

"Disc brakes" in bicycling are understood to have a separate, smaller rotor dedicated to braking and either a mechanical or hydraulic caliper system.

Extrapolating this "they're all discs" logic to automobiles would mean that it would be okay to build brakes that press against the rims of the wheels. Right.

Any modern braking system is strong enough to overwhelm the tires' grip. What makes discs so desirable is that their braking surface is far from the slop and junk on the road. They've worked great on mountain bikes for that reason, and it only makes sense that they'll work well on poor road conditions as well.

If someone's going to get all retro-grouchy and ignore new devices, they should ditch their cantis, v-brakes, and road calipers and just push spoons against the tires like in the old days.

BradBB

Well said! I find it entertaining and also tedious when folks compare discs to rim brakes as if they are winning high school debating points, yet don't see the forest for the trees.

K6-III

You're right about the Shimano Roller Brake, but the Sram i-Brake actually is a drum brake. It is the same as the brake in Sram's drum brake hubs, but bolts on and has cooling fins.

CCrew

A disc brake will stop axle rotation without a rim installed.

Shoots the "exactly" like duck in a barrel doesn't it?

dynaryder

Orly? Good to know. Them thar fancy pants words cornfuse me.

My point was that you said disc and rim brake systems were exactly the same. They're not. Sorry your sarcasm detector didn't pick up on that.

The calipers are of completely different designs,as are the braking surfaces. One is steel and dedicated for braking only,the other is usually aluminum(rarely steel or carbon) and is structurally part of the wheel itself. They're very different. Disc brakes clamp a disc rotor,rim brakes clamp the wheel's rim.

Actually,the effective limit is determined by the amount of grip the front tire has,not the brake.

dynaryder

Ah,thought the iBrake was just SRAM's version of a roller.

cyccommute 

By the same criteria, if you remove the rotor, the axle won't stop. By removing the rim, you have effectively removed the rotor on a rim brake. The principle (the point I was making and which all of you have missed so completely) of a rim brake and a disk brake are exactly the same.

cyccommute 

You can limit your definition as narrowly as you like. It does not negate the fact that the principle is exactly the same. Just because the parts are slightly different means nothing. Rim brakes can use mechanical or hydraulic calipers. Is the rim not a spinning disk? Do the calipers not press against the rim in exactly the same manner as the calipers of the smaller rotor of "disk" brakes? If not, then demonstrate how they are different.

It wouldn't matter if it were "okay" or not. If you built a car with brakes like a bicycle rim brake, i.e. where the caliper applied friction to the rim of the wheel, it would still be a disk brake. There is nothing that says that it couldn't be done. It wouldn't be as compact as the current systems but it would still be a disk brake.

Outside of some rather narrow applications - rain and wet weather riding - rim brakes work every bit as well as disks. And, in some applications, they work better than disks. Mounting racks and fenders are much easier on a bike without them. Additionally, putting discs on a touring bike takes an inherently strong, undished wheel and makes it weaker and more prone to spoke breakage which is already a problem on heavily loaded bikes.

Oh great. Another non sequitur.

cyccommute 

What I said was in response to nivekdodge's question.



Every manufacturer has a different design. Some use one piston. Some use two. Some have a fixed pad, some have a floating pad. Some use hydraulics. Some use a cable. Which one is the one, True® disc brake? If the rotor is aluminum or carbon or unobtainium, is it not a disc brake? Different materials and different mounting points don't change the basic principals involved.

All you guys have done so far is to narrow the definition further but you are still missing the point. Both rim and disk brakes use the same principle of friction against a rotating disc of metal via some kind of clamping mechanism. One just happens to be further from the hub than the other.

nmanhipot

This thread isn't going to degenerate into an argument about some arcane/esoteric discussion on the essence of disc brake technology, is it?

jeph

+1 on the modulate.

I love how they work on my MTB. Yes you can lock up the front and I have but just as quick they unlock, the sensory feedback is great. you can really get them to that razor edge for max stopping, way better than any antilock brake I have used in cars (IMHO). I often have done front wheel wheelies, especially when the traction is good. I guess an unskilled hand might send you over the bars, they are certainly powerfull enough.

I think they would be great on a road/cyclocross/commuter. Just rode in foggy weather the other day and my road bike brakes took at least a full second to wipe the water off before they worked.

BTW, my are hydrolic, never tried the mechincal ones.

a surly crosscheck is looking better all the time.

My $0.02

Jeff

Catgrrl70

Where exactly do you live?
An ice rink is manufactured ice on a flat, controlled surface. No water layer, no heat or other variables. Why do you think Seattle basically shuts down after 1" of snow? Hills, water (ok, some idiots who think they can drive in it anyway)...

I would love some Disc Brakes someday. I go through brake pads like crazy during the winter and watch my rim wear. It's not the water, it's the road grime thrown up by the water.

CCrew

As a FYI, I haven't missed anything completely. Please refer to my first post which states" If you're splitting hairs, sure. But for the sake of the OP's question they're different. "

Which part of that did you miss completely?

Dheorl

I live in good old England (temperate but soaking).

Seriously though, I'm genuinly curious now. What is stopping all this bad stuff that happens to rim brakes happening to disc brakes.

Most of the time when my rims get grimy because of poor conditions (especially on the road where I get splashed by everything else going past), the whole of my bike gets grimy. Also if you experience proper freezing rain then why don't you get ice on the discs?

edbikebabe

I'm no expert, so I'm sure someone will correct me if I'm wrong...

Disc brakes have metal pads on metal rotors. Rim brakes are rubber on metal. The metal on metal works regardless of mud or grime. Not sure about the freezing rain part.

Also - disc brakes are mounted around the hub of the wheel, so some of the grime that easily gets on the rim may not get to the rotor quite the same way.

I DO know that disc brakes allow faster stopping than rim brakes. And yes, endos are very possible with disc brakes - due to the increased stopping power & quicker engagement.

Dheorl

Even if they do still work with mud and grime, why don't they get worn out as quickly as rim brakes?

CliftonGK1

For road discs, there's less gunk that builds up on the rotor than on the rim. That means less abrasive damage to the system.
The big deal with wearing parts on a rim brake vs. a disc brake is the ease of maintenance. Pad realignment can be a tricky job for a caliper or cantilever brake without cartridge pads. The other big deal is the replacement of the "rotor" in either system. On a disc brake, you either un-do the centerlock or the 6 bolts, and pop on a new rotor. On a rim brake system, you take off the tire/tube/rimstrip, unlace the wheel, re-lace the new rim, tension and true it, then reinstall the rimstrip/tube/tire.

cyccommute 

Your first post in its entirety:

You seem to be the one splitting hairs here. Each system consist of a caliper, pad and rotating metal disk, don't they? If they share the same parts and work the same way, they how are they different? The only differences you guys have been offering is in materials. The principles of how rim or 'disk' brakes work are exactly the same. If it quacks like a duck, walks like a duck and swims like a duck but happens to be bigger, it's still a duck.

cyccommute 

You can have organic pads on disks. Organic pads, or plastic pads, are even suggested on grabby brakes like Avid Juicys. Even 'metal' pads are nothing more than metal particles embedded in a plastic matrix. You could use metal pads on rim brakes or rubber pads on discs. Neither would necessarily be an improvement in longevity of the pad in the case of discs or the braking surface in the case of the rim. If you use organic pads on a disc, they don't last as long.

Pads on rim brakes can be designed to improve braking by selection of the proper material for the conditions. Disks do work better in wet conditions...I've never argued otherwise. However, rim brakes can, and do, still work in wet conditions. I've ridden many miles in rain, snow, slush and mud with rim brakes. They still stop, you just have to be a bit more careful about how you apply them.

Disks can still suffer from the same problems, however. Get disks wet and the same principles of physics apply. Disks on a bicycle are mounted high enough that they usually keep out of the slop. Car brakes are closer to the spray and can get incredibly scary when wet. It takes a moment to sweep the water off the surface.

BarracksSi

I don't say this often, but...

cyccommute, you're an idiot.

surfjimc

That is a moronic statement. Your front brake has more stopping power than the rear, it should do the work. In theory and practice, you use both brakes; the front to stop and the rear to modulate stopping power. However, even then you are modulating both brakes to keep from the endo and skid. Quite often I only use the front when slowing, both when needed. The same holds true on my motorcycles.
Endos and skidding are caused by rider error, except in some extreme situations where you have to hit em hard to avoid a painful fall, or you ride a fixie and are into skidding and tricks.
It is sad that more people aren't taught to brake correctly.