From another thread, to avoid hi-jacking:

That's a strong argument for disc brakes. Is there an argument against them?

Weight and expense.

Not as easy to repair, meaning not as many parts available. Also, if you have a roof rack tray for a non-disc bike, you'll need to replace that tray with one that will accept a disc brake bike.

Those things said, I'm thinking of getting a disc bike for commuting as I live in Portland and it rains 8-9months out of the year here.

I love 'em, but one other potential downside is noise. The pads can occassionally rub against the rotor. I noticed when walking my son to school this morning if I tilted my bike to the right, no sound. To the left, the ringing noise from pad on rotor.

I've never used them. I passed on them when I ordered a spare wheelset for my MTB due to cost and weight. My understanding is that the mechanical disc brakes don't have much modulation. The hydraulic ones are supposed to work better, but they come with the potential leak issue.

I think if I were buying a new MTB, I would probably get them. I would not on a road bike.

Come ride with me on my off road commute in the winter. You'll wish you had them. I wouldn't go back, and yes, I can adjust canti's, V's etc. just fine.

And I'm in the PNW, too.

User problem.

Heavy, ugly, expensive thief magnets that are completely pointless for most of us. I'm convinced that 90% of people buy/want disc brakes because they suck hard at setting up and adjusting V or caliper brakes.

Is that enough? Let me know if you need more.

The biggest problem I see with them, other than cost and weight, is adding fenders and racks can be difficult. Trek/Lemond made it easier by placing the caliper inside the chainstay/seatstay junction, rather that outside, but you still have the issue up front. I'm not saying it can't be done, but it helps if you are a little creative.

Kool Stop Salmons haven't failed me, even in the PNW rain and constant moisture. Even when I build up a new bike, I'm sticking with canti's instead of discs.

I have disc brakes and am quite fond of them. For a heavier rider who rides in the rain and mud and snow and ectoplasmic semen of mother nature they come in pretty handy. I don't mind the weight and uglyness factor of them because... well... because I weigh alot and I don't think their ugliness distracts from the fact that there is a fat man on the bicycle they are attached to. Having said that, my current project bike is not going to have disc brakes, I'm sure the canti brakes will work just fine with the right pads.
Oh, and as for modulation and faceplants: they have excellant modulation, better than the rim brakes I have ridden in the past, and I have never been able to endo on this bike, maybe it's my weight, but I can't get the back wheel off the gra\ound unless I am leaning so far forward my package is resting on the handlebar.

I hear disc brakes make you stop shorter. Coworker w/ discs has done MAJOR faceplant twice now going over the bars during 'panic stop'.

The arguments have been made in other threads. I've run Kool Stop Salmons and in the rain and disc brakes just work much better. Does it matter most of the time? No. But for unexpected decelerations in the rain there is no "waiting" for your rims to dry off. The modulation of my disc brakes is fine.

I'll give you that I sucked hard at setting up my ancient cantis. Discs are much easier to maintain.

While disc brakes are the most "modern" brakes they are not 'new' at all.
What they are is a re-invention of the rim brakes to seperate you from a
few more bucks. Yep, that right "rim" brakes are , in effect, "disk" brakes
because they use the rim in place of a disc to stop the bike.

When you consider the level of mechanical complexity that "disc" brakes
add to a bike , to me, they are just gee whiz without adding any real $$
value to the bike. To me all they add is cost & weight.

Rim brakes work & work very well 99.999% of the time while being
very user friendly. There is no real advantage to "disc" brakes on a
bicycle at all.

Disc brakes are heavier and a bit more fuss but perform better and more reliably than Canti's do. My Paul canti's with fresh Kool Stop pads and properly dialed in can just match my el cheapo discs in a poor state of repair. In the muck there is no comparison in my experience.

none really

https://www.bikeforums.net/search.php?searchid=2874627

How about in snow/slush/freezing rain? I gotta believe discs would be better there. I haven't had much trouble braking in the rain with rim brakes but I'm thinking about discs for the winter.
Also I ride over gravel roads, and I get a lot of grit embedded in my brake pads; the rim brakes are really wearing through the rims, especially on my front wheel. I should maybe switch before I have to build a new wheel.

They are almost a requisite part of a trike. I have mechanical disc brakes, and modulation is pretty good IMO. No worse than rim brakes. And it's true, they are better in the rain, stay clean, and have fantastic braking power.

DISadvantages of Disc Brakes?

There are quite a few, depending on what you plan to do with the bike:

– Less choice of racks and potential conflicts with panniers. Rack selection is improving and should be less of a problem in a few years.

– Disc brakes and an appropriate disc-compatible frame are heavier then their canti equivalent. Not a real problem for touring.

– Parts harder to find, whereas there are some brake pads – not the best ones, mind you – in almost all towns and cities. However, except on a multi-year tour, it's rare that a tourer replaces pads on the road without any serious advance notice.

– The fork needs to be beefier. Which then means a less springy fork, so bumps feel harder.

– Less gracious look. But that's me.

Ugly is a practical reason??

Another advantage is that I can swap out wheels w/o readjusting the brakes. I can have 4 sets of wheels, one with skinny's, one with wider tires, one with knobbies, one with studded tires, and use them all on the same bike.

So far.. the counter points are:

Racks need adjusting before mounting.
Can't find parts readily in some backwards bombed out country on your 40000 mile tour.
Too cheap to buy it.
Too weak to ride with a few extra ounces.
Too dumb to adjust it.
Ass too soft to take the bumps.
Too inexperienced to use it properly.

Wow that's frightening the type of people who dislike disc brakes... except the guy on the 40000 mile tour, he's cool I guess.

In my experience, my discs have a lot of power but it comes on linearly, I can predict when and where it'll be so I actually have less experiences with lock up.

I've sworn that I'll never buy another bike without discs. Certainly for riding in traffic I consider them mandatory.

Some real-world disadvantages:
Harder to get a rack and pannier to fit -- but still doable, I've got two bikes set up that way.

Spoke repair is harder if you break a left-side spoke. You have to take the disc off, whereas on a non-disc bike you can sometimes do that repair with the wheel on the bike. One of my bikes has straight-pull spokes and does not have this disadvantage.

Not an inherent disadvantage, but a flaw of the Avid mechanicals my bikes have: The rear brake is the same as the front brake, with a different mounting bracket. The return spring on the rear needs to be stronger to compensate for the longer cable on the rear and the attendant friction. The rear has a tendency to stick when applied. Not really a problem for me as I haven't used the rear brake in years.

Sure, weight and cost are issues, but with any bike part you can buy things that cost less and don't work so well.

Before I had discs I went over the bars twice, haven't done it since I got discs.

Any brake should have enough power to lift the rear wheel. If it didn't I would consider it defective. What makes powerful brakes is modulation -- the ability to apply braking right up to the point where the rear wheel lifts, and then back off. This is where discs really shine, the modulation is terrific -- and it stays good, even as the brake pads wear.

A well-adjusted rim brake, on a perfectly true wheel, can also have good modulation. The problem, particularly for commuters, is that it is very easy for a rim brake to go out of adjustment, or for a wheel to go slightly out of true. When I had rim brakes I found that I just didn't adjust them as often as I needed to, and I often was riding with sub-standard brakes.

I'm considering putting a disc on the front and leave the v-brake on the rear of my commute bike. I hate the noise my rim brakes create when I don't keep the rims clean. I had them adjusted perfectly...no noise and stopped great. That lasted for about a week. Now the squeel again.

I want to run panniers and a rack, and dont want to deal with the rack if I have to fix a rear flat. Plus the rtear brakes don't do a whole lot anyway.