pkulak

Wow, this thread has taken on a life of it's own. Just as an update, I'm done with disc brakes. It's a long story, but I got myself a a Kona Jake instead. Now I have cantilever brakes, and they suck about as bad as my disc brakes, but at least I can mount normal fenders and racks now (and my trailer hitch), the new bike is substantially lighter, and at some point I'll upgrade the stock cantis to hopefully get stopping power I'll be comfortable with (or maybe just get a smaller transverse cable).

If you want a bit of the long story, the bike shop I bought my Norco CCX3 from is actually returning my bike and the rest of their stock to Norco. The owner said he's not happy with the mounting tabs on the front fork (it made getting the pads adjusted properly nearly impossible). So, it totally may be that discs _are_ awesome, but there were some issues with that bike that made adjusting them impossible. Regardless, I'm going to stick to rim brakes for the time being.

canyoneagle

It might be worth popping a message in the cx forums to get some input on cantis.
I hear the Paul's are awesome, and know that Avid and Tektro both offer some highy regarded models.

Grats on the change! Sounds like you had an out of spec bike, which would explain your experience.

Though I am a disc convert, I must say that (to me) the biggest tradeoff is ride quality. In order for a fork to handle the specific loads at the caliper, it must be beefed up substantially, making for a much stiffer fork. This does affect the ride quality, though some changes can be made to the overall bike geometry (slacker head tube angle, larger for offset to maintain trail) to allow for a compliant ride.

cyccommute 

Cantilevers are more difficult to set up than a v-brake but this article will help: Adjusting cantilever brakes. I suspect that your straddle cable (or link wire if the Jake uses one) is too long. That's usually the issue with cantilevers. I don't personally agree with Sheldon Brown on the link wire, however. I find a straddle cable works better and is more adjustable.

Andy_K 

That's a slippery slope, but you'll always have plenty to do. With most brakes you set 'em up one way and you can confidently say that they are "properly" adjusted. With cantilevers, something can always be just a tiny bit better.

MileHighMark

It's not necessary, but it greatly improves performance, especially on the road version. The road version's "ramp-up" is very different than the mtb version, and the former works noticeably better when you pre-load the actuator arm.

Andy_K 

They can fail if you're a complete bozo. Read this for a description of what that's like. The failure described at that link may be hydraulic-specific.

You're actually in the ideal setup, because you can use your rear brake to scrub speed on descents (which is safer anyway), while saving the front brake for actually stopping. Someone will immediately jump in to lecture me about why using the rear brake in this way is wrong, but I think on a long, steep descent with a front disc brake it makes sense. Of course, with enough abuse on a descent you can get a rim brake to fail too. On the other hand, who needs to slow down.

Andy_K 

I had't heard this before. Do you get a different effect by pre-loading the actuator arm than just adjusting the pads closer to the rotor?

MileHighMark

It's hard to explain the difference, but it does feel different than just adjusting the (outer) pad closer to the rotor. As a side benefit, I've found that I can actually run my pads farther out and still get plenty of stopping power (although I prefer that all my bikes' brakes not engage until the levers are very close to the handlebars).

drbenjamin

That's surprising. I wonder if the screw pitch is variable, so that there's a different mechanical advantage depending on how far rotated the actuator is.

Mine have always seemed a bit mushy, and I just ordered some compressionless brake housing, so when I redo the cables I'll try your trick.

AndreyT

I'm using the right levers with BB7. My bicycle is equipped with SRAM Apex group.

The advice about pre-tensioning the cable comes from the simple fact that moving the actuator arm on BB7 makes the pads to spread apart at first (!). They move away from the rotor for the very small fraction of the initial movement of the actuator arm. And only after that, as one continues to move the arm, the pads begin to close and grab the disk. This behavior is easily observable from the outside. When I saw it for the very first time, I though that my BB7 might be defective, but further investigation and testing of several brand new BB7 packages revealed exactly the same behavior (not even mentioning that it has been reported by other users before).

I believe it is caused by some amount of lateral play that is always present in the actuator mechanism. The "screw" of the actuator can wobble from side to side in the caliper. When one begins to pull the cable, the first thing that happens is that the actuator screw tips up, under the force applied by the cable to the actuator arm. And only after that the actuator arm begins to move and the "screw" begins to rotate, closing the pads around the disc. That initial tipping motion changes the alignment of brake pads (and is often seen from outside as brake pads "spreading apart"). This initial realigning effect is exactly what we are trying to dial out be pre-tensioning the actuator arm. Note, that we are not really trying to move the arm per se. What we are trying to do is to dial out the lateral play of the actuator mechanism. Of course, in practice it normally means that we move the actuator arm up a very tiny bit before tightening the pinch bolt.

Pre-tensioning the actuator arm is not absolutely necessary. I used my brakes without pre-tensioning the arm for a while and they worked fine. Again, they will work fine without any pre-tensioning, if aligned properly. However, when the arm is ever-so-slightly pre-tensioned, just to dial out that extremely minimal initial portion of its movement range that makes the pads to spread/realigh, the brake feel improves noticeably. It also becomes much easier to adjust the pads for that ideal position where they don't drag and at the same time respond instantly, with minimal "dead zone" on the brake levers.

KLW2

I find that holding one's arms close to the torso allows for a more aerodynamic flight as one passes over the stem bolts and garners more points from one's riding buddys. Mine are hydraulic and that is how I broke them in.....

digger

I've used a number of different brake systems over the last 25 years (with the exception of hydro disc brakes) and I find that the mechanical disc stop no better than linear pull or cantis (that are properly setup).

I do find that _quality_ disc brakes (in my experience) are better in frozen conditions and wet/mud. They are not affected by ice or water/mud like rim brakes. So in that respect, they are better. In the dry, no difference.

I have BB5_mtn on my commuter and BB7_mtn on my mtb bike. The BB7s are far superior than the BB5. I had Tektro disc brakes on another bike, and I felt like an oil tanker....I needed 2 miles to stop. Slight exaggeration there, but they were crap.

The BB5s were better than the Tektros, but a son of a gun to setup.
Like many I had to pre-tension the actuator arm for them to work properly. I have since discovered the business card trick to setup BB5 disc brakes, with no need to pretension the actuator arm.
https://www.ecovelo.info/2011/04/15/a...5-disc-brakes/
https://bikeshopgirl.com/2011/08/how-...id-bb5-brakes/

I am very happy with the BB7 brake system using XT levers. However, high quality rotors, cables and housing make all the difference. The rotors I have are XTR 6 inch. Unfortunately, the tab on the brake pad will strike the arm of the rotor, so I have to cut off the tab from the inboard brake pad.

There are advantages and disadvantages of rim and disc brakes. In a nutshell, I use disc brakes due to the muddy off-road riding conditons that would grind through a set of rims in one season. If you ride in dry conditions, then mechanical disc brakes would offer no advantage.

I can't comment on hydro brakes as I have no experience. But they come with yet another set of advantages and disadvantages.

digger

Agreed, cantis are a challenge. The cantis of the late 80s and 90s was were I learned how to swear most efficiently.

I find the Avid Shortys on my touring bike quite setup friendly though. They come highly recommended from me.

I'm on the fence with yoke vs link wire. The yoke is adjustable fershizzle, but if one uses the right length link wire then I find it better. The Avid Shortys came with 3 differant lengths, I was impressed!

cyccommute 

Why? I'm not being facetious either. I see this all the time with people setting up their levers so that the brakes don't even engage until the lever is pulled half way but I really don't understand the thinking behind it. I've ridden a few bikes with that set up and have always found the braking to be uncomfortably slow and the lever perilously close to bottoming out.

All of my brakes are set so the brake engages immediately and if the lever reaches the halfway point the wheel is locked. That's the problem I was having with the BB7 before I found the proper adjustment method. The brake didn't even engage until half way and the levers were almost at the bar before the bike was stopped.

cyccommute 

Based on my experience, the mechanical discs aren't any easier to set up than cantilevers are. Both involve a fair amount of voodoo but with cantis, at least, you can see what you are doing.

My problem with the link wire is that too often the link wire is too long. That makes for mushy brakes. A straddle cable can be adjusted more easily to tune the brake better.

alan s 

My experience with hydraulic disc brakes is they have better modulation and require less force on the levers than mechanical brakes of all types. The system is sealed. They work great. All advantages and no real disadvantages.

ItsJustMe

Like Cyccommute, I like my brakes to engage fast and have no chance of bottoming out. I keep my brakes adjusted to where they're as close as possible to actually dragging as I can get them. Generally on the BB7s I adjust the inside disc first then the outside, in each case I adjust up, then apply and release the brakes and spin the wheel, if they don't drag give them another click or two, when they start to drag, back off a couple of clicks.

digger

I find that odd as well. The standard my LBS uses is when the lever is about 1 inch from the handlebar, then the brake will engage. Too me, as Cyccommute states, this is very close to bottoming out. My brakes are setup so that there is very little movement in the lever before those brakes are on.

My experience differs from Cyccommute with the BB7s. I have no trouble setting them up so my levers engage almost immediately. Now with the BB5s, this is nigh on impossible, and I have to settle for more lever movement. Even with the busines card trick.

BB5s, I agree with you, like the cantis of the past they are a very frustrating setup.

BB7s, I disagree. BB7s are much more easier for setup than cantis or linear pull. Just my experience. I often find it is usually some little nuance that one guy or gal does that makes a world of difference.

digger

Ok, I see.

Wouldn't there be a bit more of a weight penalty? What about busting a line when cycling? Is that a concern, or does it happen inoften?

digger

That is exactly what i do with my BB7s. No need to touch the barrel adjuster nor pre-tension the actuator arm.

BB5s.....not so much. The business card trick helps immensly and some fiddling (cheating) with the actuator arm.

alan s 

Weight penalty? Even if there is one, and I've never checked, I'm not counting grams on a commuter bike. Never busted a line. But if I did bust a line, I have a back up brake. Same as if a brake cable snapped.

AndreyT

If your purpose is to get it "as close as possible to actually dragging", as stated by ItsJustMe, then you are doing it wrong. There's no way to get the pads "as close as possible to actually dragging" without pre-tensioning the arm. If you are not pre-tensioning the arm, it means that you are leaving a rather generous amount of "dead" travel for your pads. As I said above, BB7 can and will work adequately without pre-tensioning, but dialing-out that "dead zone" makes a world of a difference in brake feel and responsiveness.

MileHighMark

I set them this way because I have more control when my hand is (more) closed like a fist.

digger

I'm not sure I understand. I'm happy to talk about it and perhaps I misunderstood what ItsJustMe stated. If memory serves this is what I did..and do.

I'll take it from when caliper is first installed.

To align caliper, insert new pads and tighten pads down onto rotor with rotor centered in the caliper. I think Avid states about 1/3 outboard and 2/3 inboard. I find this does not work well.
Tighten caliper bolts
Tighten pinch bolt on cable
Prestretch your cable by pulling on it a few times, use a rag to protect your hand
Readjust cable in the pinch bolt.
Back off the pads until the rotor is free.
At this point, and this is what I understood from ItsJustMe;
Pull and release the lever a few times, spin wheel
Adjust each pad until you here it start to rub the rotor, back off each until rubbing stops.
Pull and release lever, spin and check. May rub slightly, may not.
Adjust the pad, or pads in until rubbing starts, back off and recheck lever. You may have to put up with some slight rotor rubbing.

The success of that last step will depend on the trueness of the rotor.

Some cable slack MAY, I say MAY, be need to be removed by turning the barrel adjuster usually after 1 or 2 rides when cable stretches a little more. Or you can readjust teh cable in the pinch bolt. I find that a 1/4 turn just about does it.

If I missed a step, or perhaps I am unable to adequetly describe it, therefore I apologize.

All I can say is that the brake lever moves very little, perhaps 1/8 to 1/4 of the distance to the handlebar using this methodology. But not the 3/4 of the distance for a 1 inch clearance from the bar, before the brake engages, like the LBS sets them up.

digger

Ok I see. Everyone is different.

I like to use one finger, just inside that hook on the end of the lever. "Back in the day" when we had something like 6 finger levers, then this "fist" type braking style was the norm.