MrPolak

Can someone explain to me why discs are bad when they are so good? Does anyone who's against discs on a touring bike have any anecdotal advice? I'd like to hear about your negative experience with discs on tour that caused you to switch back to cantilevers.

foamy

Disc's aren't bad. Their modulation and smoothness are great. I was astounded by their smooth, sure stopping power. I just don't prefer them.

They weigh more.
They're down there around the axel and can get in the way. You have to work around them.
It's something else I'd have to learn how to fix. I know canti's, vee's and calipers.
More parts.
I'm given to understand that they apply different forces/stresses on the wheel—spokes in particular. Someone else who understands that aspect better can fill you in. Cyccommute, I believe, gave a rational explanation.

Anyway, those reasons won't hold water for a lot of folks and that's all right. As I said—it's personal preference. As most things are. I don't think they're bad at all, I just don't prefer them. It's mostly about the weight and added complexity for me.

NeilGunton

There have been some issues with disc brakes, some of which I have only heard about, others which I have seen for myself:

1. Anecdotal: They are very strong, and so if you brake too hard with the front brake, you risk going over the handlebars. I don't know how true this is, but I think I've read it on occasion.
2. Anecdotal: The front disc brake puts a lot of tortion stress on the wheel, which tends to pull it out of the dropout, thus producing the possibility of a catastrophic crash on bikes with quick release hubs that haven't been tightened properly. I don't know if this is still an issue, since all front forks now seem to have "lawyer lips" which prevent the wheel from disengaging unless the quick release is manually loosened.
3. Anecdotal: Fork stress. The tortion causes stresses to be put on the fork, which could cause handling problems or even failure. Some bike makers (e.g. Tout Terrain) make forks specially strengthened to compensate.
4. Personal experience: Clearances can be complicated for mounting racks and kickstands. The disc brake housing tends to go just where you want to be attaching these things. For example, I cannot put a standard rear rack on my Novara Safari because of the disc brake mount position and housing; also, I cannot mount my favorite kickstand, the Greenfield.
5. Debatable: Complexity, and less availability of parts abroad, since disc brakes are relatively newer than the classic cantis.

Having said all that, there are benefits to disc brakes:

1. They are indeed very strong! Good for stopping a loaded bicycle on steep downhills.
2. Less risk of blowing out your tires on long descents because of heated up rims
3. Less wear on your rims, thus lengthening their useful life
4. If your rim goes out of true, then it doesn't affect braking
5. You could, on bikes with enough clearance, use either 700C or 26" wheels.
6. Disc brake pads tend to last a lot longer than rim brake pads
7. Better braking in the wet, and less clogging in muddy or snowy conditions

I guess there are pros and cons to any system; it depends on what is important to you and what you're willing to put up with.

Neil

Muttsta

They aren't bad, I love mine. I toured from Alaska to Panama on disc brakes. You just have to know how to adjust them because occasionally they misalign and cause an annoying 'brushing' sound.
The biggest downside of them is that if they break, parts are hard to find for them in remote areas, but overall I love mine.
They stop me down the steepest hills in any type of condition.

nancy sv

We had them on the triple - three people on a fully loaded bike = heavy and hard to stop. That being said - they were a pain in the rear. Every time we had a flat tire we had to unhook it and then hook it up again - which was a bit of apain. Would we do it again? In a heartbeat. Would I put them on a hot-so-heavy single bike? Probably not.

nancy sv

Oh wait - we had a DRUM brake, not a disc. Never mind what I said above...

Niles H.

It would clarify the issue to use a more specific category, rather than the broad category of 'disc brakes.'

There are significant differences among the different companies and models.

These include some major differences in reliability and durability, ease of adjustment, soundness of design and engineering, feel and modulation, quality of construction, simplicity/complexity, frequency of maintenance and repairs, and mtbf, among others.

Some are easier to learn about and easier to service.

Rowan

One significant drawback is that many of the bikes used for touring don't have the lugs required to fit disc brakes either on the fork or the rear left dropout.

I have just acquired my first-ever pair of disc brakes for an MTB project, and pair of Hayes MX1 with cable actuation. I have the fork to fit them, but now I am perplexed by the fact that the frame (yes, another dump retrieval, but an OK one) doesn't have the rear lugs, and I am looking at acquiring a new frame that does. But then I could just go with V-brakes on the rear. Decisions, decisions...

Having just set up the front hub on the fork, I found the adjustment to get pad clearance to be extremely simple. As to on-the-road adjustment to avoid rubbing... well, I don't think it would be any more difficult. Adjustment of hydaulic calipers might be different.

Carrying two or three pairs of replacement pads also would be nothing compared with pads for cartridges for any rim brake.

The benefits were outlined well by Neil. I think that as far as the problems go, you only have to look at the experience of the MTBer. The drop-out issues were major ones, I think, when poorly designed forks were placed on the market. But they have been redesigned, I believe, so the leverages on the axle won't pull the wheel off. Looking at my Magura Odur, the drop-out itself has a different angle, there are lips around the dropout, and the caliper mounting tabs obviously are placed behind the leg. Of course, the through-bolt system has now been adopted to make absolutely sure wheels won't come off.

The issues of torsional stress on the spokes I don't see as valid when compared with the stresses of normal riding uphill in very low gears with a heavy load. As to stress on the hub and bearings, that might be a different issue.

The only major drawback I can see is damage or distortion to the rotor caused by a fall against a object.

Niles H.

Part of this is inertia.

Often when something new arrives on the scene, there is some period of lag time. There is some prejudice or doubt, some habit or attachment to tradition.

This seems to happen in many fields. Touring is one of them.

There are other aspects of touring bikes that also suffer from this.

Niles H.

Also, early versions tend to have bugs. Even long after the bugs have been worked out, rumors and residual attitudes tend to linger.

Niles H.

Some models have problems staying in proper adjustment. They can make very annoying sounds.

Some people just give up and turn back.

The Figment

I use Shimano M-475 (Deore) Cable Discs on my bike,with Shimano Deore Vee-Brake levers.I carry an extra caliber,cable and two sets of spare pads,Cheap,VERY Effective,Bombproof...Sorry,but I will never go back to rim brakes...Ever!!!

Niles H.

Many touring bikes just are not set up to accommodate them.

Many people stay with what they have.

There isn't much demand for touring bikes period (compared with other segments of the bike market), and there is even less demand for touring bikes with disc brakes (for various reasons, some of which are mentioned above).

Sheldon Brown has said that eventually discs will overcome and predominate.

It takes some years though.

Niles H.

Peter White talked me out of disc brakes. He said that good, properly adjusted cantilevers do just fine. Yes, [some] disc brakes are 'stronger': but that is meaningless [according to PW, in that conversation] because if the cantis can freeze the wheels, you can't do any better than that.

Even in the rain, I wondered.

Yes, he said.

He talked about his own bike, and how he could lock the wheels under any conditions, including mud.

*******
[I remained somewhat skeptical, but this was his way of seeing it.... He thought that discs were just expensive and unnecessary, even on tandems.]

[He also seemed to think that most people do not get the most out of their cantis.]

vik 

I have disc brakes on some of my bikes, cantis on some and road bike calipers on a couple. I don't really think any of these systems is perfect for every application. My touring bikes have v-brakes and I have no issues with stopping power rain or shine. I don't overheat my rims in the mtns.

I use v-brakes because:
- allows you to use a fork with vertical compliance to absorb road vibration
- inexpensive $25 a pair
- lots of stopping power
- modulate well
- easy to adjust
- easy to get parts for
- light
- simple
- easy to repair
- doesn't require dish in front wheel and less dish on rear than disc
- not easily damaged during transport

Disc brakes do have some advantages:
- better in all weather, especially winter & mud
- better for really heavy loads as you can get bigger discs [however - you need an appropriately strong fork/frame or all you do is damage your bike under severe braking]

However, there is no magic bullet and unless you are riding an Xtracycle hauling a ton or winter commuting or off road touring down muddy tracks I don't think they add much value to your bike while making it much less likely to be repairable internationally.

One often quoted reason to get discs is to avoid over heating rims. First off read this article and appreciate your discs only have a finite heat capacity before they are damaged. Second consider that you may be using your brakes poorly. Applying the brakes constantly for a long duration is a recipe for disaster. Shorter stronger applications allow your discs and rims to cool down in the air flow. You can validate this yourself. Go down the same long hill twice apply your brakes lightly, but consistently the whole way down to keep a constant speed. Then try the same hill again and keep the same approximate speed by applying your brakes strongly and then letting them off for a bit - repeat. Check the rims at the bottom - which are warmer.

Quote from the article I linked to above - it talks about tandems, but a heavily loaded touring bike has the same issues:

"Tandemists who are using the current crop of mountain bike disc brakes on their tandem should keep in mind that none of the current disc brakes are designed for tandem use. All of the current disc rotors are too small and light for tandem loads on big hills with heavy teams. Some of the rotors are too light even for light teams on medium hills. In the right conditions, the rotor will overheat too quickly because of its low mass (and therefore low capacity to absorb braking heat).

Certain people are successfully using existing single-bike disc brakes on tandems, without risk of brake failure. Those people ride in flat places with no big hills. The next question those people may wish to ask themselves is why they have bothered with the expense, complexity and extra weight of disc brakes when rim brakes would have offered perfectly adequate performance.

Rim brakes on a 700c or 26" wheel have a mechanical advantage over a typical 8" disc brake because the radius of the braking surface is much smaller on a disc rotor than on the wheel rim. Much more braking power can be applied with the rim brake (about 10 times more, thanks to the miracle of leverage)."

I'm not suggesting disc brakes are bad or they should not be used. However, there seems to be a very simplistic view of how brakes perform that suggests discs are better than a canti brake without factual basis for this argument.

Rowan

One of the furphies about rim brakes is their ease of setting up. Sheldon Brown has some interesting things to say about mechanical advantage and being able to get the most efficiency from cantis. Most people aren't aware of these issues and blythely adjust their brakes anyway.

There are issues with straddle cable length and others such as such as toe-in related to brake squeal. And the fundamental design parameters of various canti and V brakes can influence stopping efficiency. Just getting the pads aligned correctly on the rim can be a challenge. V brakes don't escape criticism here, either, if you run standard STI braking systems -- setting up a Travel Agent can be an interesting exercise, too.

Having just set up a disc brake on the bench... well it was just soooooo easy. The proof will be in the riding, of course.

But a critical factor not really highlighted yet in this discussion is the longevity of rims. Take the pad quality of V and canti brakes. Shimano pads are renowned for being very abrasive on rims. Koolstops have a reputation for being relatively gentle, but I have worn a Velocity Aerohead front wheel to a point of concern.

Most importantly, there are the conditions, and I am not talking about braking efficiency here -- I am talking about if you ride in wet, gritty conditions that will wear away the rim wall rapidly. A (real) advantage of disc brakes is that they rotate away from crud on the road, and are less prone to wear because they don't pick up the grit so much. Plus, you don't have horrible grey masses of fine brake dust oozing all over your rims, tyres, frame and clothing.

I am interested comments from long-term users of both types of brakes as to how long their rotors and their rims last under the respective systems in similar riding conditions.

I am not sure, also, that it is entirely fair to compare the efficiency of either brake by using tandems as the basis. No touring bike is going to be ridden with another person plus luggage on board, as well as the extra mass of the frame. The issues of overheating might be real in very very tortuous conditions, but why do not the same principles of cadence braking (on-off-on-off) apply to disc brakes?

I went with mechanical discs because of their simplicity in set-up and adjustment. I have dealt with hydraulics in other automotive arenas and they can be finickity if (a) your seals aren't totally sealed, (b) everything isn't totally (surgically) clean when servicing and (c) you don't use alcohol to clean the system (there are others, but that's a start). Above all, it's much easier to replace a broken or bent cable than it is to source a new hydraulic hose and the associated paraphenalia to connect it (which also could be read as a positive for rim brakes).

It's also worth pointing out that rim brakes are in fact disc brakes in of themselves.

Niles H.

From another perspective, they are bad because they can lead to liability problems.

Many bike manufacturers pay attention to potential liability issues.

Disc brakes have had some unexpected consequences that have led to lawsuits.

The QR is initially restrained by the retention lip on the fork (assuming it is present), however over time the slipping of the quick release leads it to unscrew, which is described here. Once it has unscrewed enough, it can be forced over the retention lip and the rider will crash.

Some further discussion of these and related issues here:

https://www.ne.jp/asahi/julesandjames...quick_release/

*******
In addition to the liability issues, there are the safety issues.

'The QR is initially restrained by the retention lip on the fork (assuming it is present), however over time the slipping of the quick release leads it to unscrew, which is described here. Once it has unscrewed enough, it can be forced over the retention lip and the rider will crash....'

So even with a retention lip there can be problems, and I would respectfully disagree with

and
which isn't always the case.

Niles H.

The advantages of ceramic rims may be relevant to consider. Among other things, they allow rim brakes to be used in abrasive (muddy, gritty...) conditions without rapid rim wear. They also tend to be better in wet conditions, with some brake setups at least.

Under similar conditions of use, they last much longer than standard rims.

[They do tend to wear out brake pads more quickly, even though the pads are much harder and more resistant to wear than the pads used with non-ceramic rims.]

Rowan

Riding ANY bike with ANY equipment can lead to liability issues. I have seen MANY riders with rim brakes who didn't have a clue about doing up QRs and wondered why their bikes handles like rubbish. In one case, the non-disc-brake suspension fork on a hire bike of mine was damaged severely in an incident just like this. It was entirely operator error for not reassembling the bike as instructed after they travelled by motor vehicle to their ride venue.

The incident you point to is relatively old. The issue of fork design and particularly the placement of the mounting tabs for the calipers on the forks came to light in the early 2000s. I haven't seen many posts in the MTB forum here talking about lost front wheels since then. The two related design factors, as I remember the discussions at the time, were the angle of the dropout, particularly if they were vertical, and the tab position and the leverage or turning effect that created on the axle.

Rowan

You are talking from personal experience on this, of course?

vik 

I can mount and adjust either a set of v-brakes or a set of avid BB-7's in about the same time. Neither is particularly hard and both require some care and knowledge to get the best performance out of them. I've seen poorly adjusted discs and cantis.

Rim life will be better on a disc rim for sure, but what is better and does it matter? For a rainy/winter commuter or a tour through mud or really wet dirt roads I'd lean towards discs as they don't wear out your rims as fast. For just about anything else rim wear has never been a factor. This obviously depends a lot on the rider and situation - I've never been hard on brakes or rims - I can't explain why other people burn through pads/rims so fast???

I've gone through Avid BB-7 pads faster than I have kool stop v-brake pads. Not really a huge deal as both kinds of pads are small and light enough that carrying spares is a non-issue. I've not worn through a rotor yet.

I posted the tandem link as an example of the issues discs face during hard use. There was a German mtb bike magazine article that compared how much heat various braking systems could take before failure. The disc systems failed at around the same heat that rim brakes blew out tubes - unfortunately my link to that article no longer works. The problem with over heating IMO isn't the type of brake, but how it is used. I don't think a normal fully loaded touring bike should have brake overheating issues in the mountains with either rim brakes or disc brakes if used correctly, but I wanted to emphasize you can over heat and essentially destroy your rotor on a disc brake just like you can overheat a rim on a rim brake and blow out a tube.

All my discs are mechanical cable actuated. I don't trust hydraulics for a travel bike and for a bike I use in town I'd just as soon stick with cables as they are easy to work with. You might convince me to use a hydraulic disc for winter commuting. I have an original Avid disc brake - essentially a BB-7 which is 7 years old and going strong. I also have a new set of BB-7s and they both functional identically.

Niles H.

It's still "the early 2000s" and this incident did not occur that long ago. There are still plenty of bikes being used that were from that time.

*******
"Riding any bike with any equipment can lead to liability issues" does not mean that disc brakes do not have their own set of concerns.

Rowan

The website you refer to says "Updated January 2006". That's now over two years ago. The links are circular and add nothing to the information. But knowing the way things move slowly in legal matters like this, I'd say the incident likely occurred in 2002 or 2003 at the latest.

And rather than having the option of using 1990s, 1980s, etc, just how do you want me to describe the first decade of what we are in? Read my reference to early 2000s and being early in this decade... which is well and truly past half way.

NoReg

Brakes are the most troublesome part of the component search for touring bikes due to the difficulty of matching road levers to various styles of frame and long reach powerful brake. So whatever the faults of discs it isn't as though all the other options are easy in every case either.

Generally the discussion starts and ends with the cable actuated version of disc brakes. For better or worse there seems to be an agreement that a hydraulic brake systems on a touring bikes is too complicated for easy field service. Also, most touring bikes do not encounter the kind of mud that stops rim caliper brakes dead in their tracks. So two of the main advantages of "discs" die before we even start the discussion.

- Wheel separation issues should be dealt with, not used as an excuse for not mounting discs. I wouldn't by choice have quick releases on any touring bike. My mom's touring bike had a nice compromise, solid axles with butterfly nuts on them. Another option would be pullable axles as on motorcycles and enclosed drops. Lawyer lips may also helps, so possibly uber bike makers/users should stop the name calling.

- Discs do weigh more, and the forks they run weigh more. Fully loaded touring bikes probably should be dropping the wimpy forks anyway. The fiddly tapered tubing in a lot of touring bikes is a nice vintage look but just as heavy as straighter stronger forks (the thin ends are swaged and have near the same metal in them). The idea there is a lot of useful compliance happening is scary if anything, on a touring bike, that is the job of the tires.

- Easy to adjust, and stay adjusted if the rim wows, better than the rest in this regard.

- Run with either kind of levers required for drops or bars, though you need the right caliper.

- Discs can be fragile, but the are also light and easy to replace, and they are easily found in bike shops in the first world.

- There are rack mounting problems, but they are only integrative. There is no serious difficulty if the discs are designed in as part of the package from the beginning.

- Wheel strength problems are twofold, one is the tweak put on the spokes when stopping, and the other is the need to dish the wheel on the left side also, wherever there is a brake mounted. It's not good news, but it can be dealt with, by solid building technique, and also by future potential mods like a wider than 100 front hubs.

- Disc systems aren't particularly expensive, but they require an added BO on the frame, and also the Avid brake itself. You can pick them up for under 50 per wheel at times, and that is cheap compared to premium rim brakes, but very expensive compared to the kind of tripe that gets fitted to a stock touring bikes, and might cost 10 bucks a pair of brakes.

- It probably is true that discs are not super familiar among tourist. Though for anyone who follows cycling, disc brakes are one of a handful of big gets the cycling industry worked on for a decade, and every tiny improvement was much written about in the mags. Think of discs; hydraulic brakes of any kind; suspension; better shifting derailleur and clusters; aero wheels, etc... Maybe today, tubeless tires.

- Discs are ugly. They have a lot of nooks that catch dirt. There isn't anything really clean in the way of an install like an Exile sprotor mounted, drive side brake on a Harley. Imagine if they had something like that and the hydro was wired through the frame for a cleaner look.

- Some of these issues go away if you mount only a front disc, or a front disc and second brake system. How likely would you be to pop off the front wheel if it was only 50% of your braking force? How serious a problem would hydraulic reparability be if you could fall back on a second brake?

- The final problem with discs is that calipers can be made to work, and they are rather beautiful to boot, cheap, and accounted for on most frames. If it ain't broke don't fix it. I think that is a fair attitude, as long as one keeps an open mind to the circumstances in which rim brakes are a somewhat limited system.

I think in taking anecdotes about stuff like bikes flipping (gotta be a severe downhill in the woods somewhere). Or Thorn's caution on discs, one should consider the source. If you sell bikes with touring style forks and outfit them with flat bars and MTB discs, stuff may happen. I don't think that package of ideas is going to travel well to every bike.

Rowan

V brakes are a slightly different kettle of fish, and I deliberately didn't lump them in with cantilever brakes. Are you? I still hold that adjusting cantis can be a chore. V-brakes less so.

The point I was making about rim life is a reality for a lot of people. Everyone has different riding styles, so people who work their brakes hard will wear out their rims faster. Likewise those who ride in wet and gritty conditons. Is it better to run the risk of a cracked rim in the middle of nowhere and be immobilised? Or to have a rotor warp (the most likely scenario) and remove it and keep riding on the rear brake?