Advantage of Disc Brakes?
 

I am pondering getting a disc brake equipped bike. Do they have any advantages over a rim brake equipped bike?

Yes and no. Depends on your riding style, terrain etc....
Personally, I don't like the "vulnerability" of the rotor when little brats jamb their bike against yours in bike racks etc.

Mine outperform rim brakes in wet/slick conditions. So if you do a lot of riding in those conditions, then they are the right tool for you.

Rim brakes are equal on dry roads. Rim brakes work in slick conditions, but you just have to be more careful.

Disc brake works a lot better in the wet/muddy condition than traditional rim brakes and have consistent braking.
I love hydraulic disc brakes as they automatically adjust the pads as they wear down.

The rims aren't worn down. Care must be taken when handling the wheel off the bike to not bend the rotor.

My opinion is consistent with what others have said, but I'll try to add some explanation (and a couple more points).

1) The talk of disc brakes being obviously stronger in good weather is largely marketing hype. As others in this thread have noted, discs aren't "better at being brakes" in dry weather. The increased clamping force of discs are canceled out by the much smaller disc diameter compared to a rim.
2) Disc brakes are generally better in wet/mud for two reasons: (a) the disc is further from the ground, and doesn't get wet or muddy just based on what the bike wheel is rolling through (b) wet rims need a revolution under the brake pads to scrape the water off for better friction between rim and pad. Disc brakes have higher clamping force, which squeezes the water out from between pad and braking surface almost instantly.

Other relative upsides of disc brakes:
3) you can easily swap between different wheel sizes on the same frame
4) no need to replace the rim once the braking surface is worn down. this matters more for commuting bikes (where braking is more frequent and rims will thus wear down more quickly)
5) easier to use with fatter tires and/or fenders, where longer arms of normal sidepull brakes will mean more flexing and less braking force (this advantage disappears when comparing disc brakes with centerpull rim brakes)

Other relative upsides of rim brakes:
6) less finnicky adjustment when changing wheels, because tolerances are larger
7) a flexible fork (which gives a smoother ride) can be used, whereas disc brakes require a stiffer fork.
8) pads are less likely to "fade" from overheating on long descents, because large rim (esp aluminum) acts as a better heat sink than small steel disc
9) less aerodynamic drag in crosswinds
10) brake pads last a lot longer. numerous reports of disc brake pads wearing down quickly.

All this means that disc brakes are obviously better for off-road usage.
For road riding, things are much less clear. Disc brakes are more likely worth it if you live in rainy conditions, where you'll get better power and won't need to replace your rims when the braking surface wears out.

Jan Heine of Bicycle Quarterly (who rides fatter-tire road bikes in all-weather conditions, with centerpull rim brakes on some bikes and discs on others) recently wrote a general overview of disc brake pros and cons

My very first disk brake equipped bike is my daily commuter. It took a bit to get used to them. I was squeezing to hard when coming to a stop and I had a few minor crashes. I am much better now. I really like them for commuting as I am always stopping and going. As other forum members have mentioned, disk brakes are not effected by rain. I can't imagine my commuter not having disk brakes any more. They have made my commute much safer.

Yuppers. I'd also add.... Larger tires are possible versus traditional caliper brakes. Also details like thru-axles in your frameset and wheels grant stronger wheels (which on offroad makes for better for steering).

I had wider tires at #5 (though it's buried in a longer list)

I don't think there's technically anything keeping thru-axles from being used with rim brakes. My sense is that they developed in part because of the asymmetrical forces on frame/fork that come with disc brakes. but as mostly a roadie, I'm not an expert on this one.

I've commuted with rim brakes for years, often in the rain, and have never worried for my safety. In my experience, rim brakes are worse in the wet, but not by an order of magnitude.

Down side for me has been ....wheels. Getting disc brake wheels with thru axle is nothing. Then look at 36 spoke wheels,disc brake and thru axle the numbers narrow down quickly.
However as a Clyde I do like my disc.

And to not pull the brake lever lest you extend the pads too far to get the wheel back in without having to use a tool to push them back.

There's no direct link between wheel strength and thru-axles. Wheel strength comes from things like flange diameter/ spacing, spoke count/diameter etc
The advantage you can get from thru-axles is that they tie the left and right side of the fork/frame together more rigidly, which makes the frame/fork overall stiffer.

A thru-axle wheel may well be stronger, but not b/c its a thru-axle.

I find even under dry conditions that my hydraulic disc brakes are a major improvement over rim brakes, probably because I do a lot of riding in very steep hills and off-road, and I make very heavy use of the brakes. Being sub-clinically paranoid after a significant injury probably doesn't help either, but I find they have given me a lot more confidence.

Having said that, I recently put new rims and Campy rim brakes on a different road bike, and I would say they are at least 80% as effective. My hands do hurt more, however, when I use conventional brakes for long descents.

For me, the main irritations are finicky adjustment and frequent replacement of pads as well as rotors. The other thing is I highly recommend thru-axle, especially in the front, if you get disc brakes. I don't have it, but I wish I did. Because of the way the front brake caliper mounts on most forks, the force vector points down, which tends to push the wheel out of the fork dropouts. (My Enve 1st gen cyclocross fork has forward-pointing dropouts, which is a bit better, but they obviously decided thru-axle was an improvement, because the next gen of cyclocross fork is thru-axle.)

I also recommend Shimano (vs. SRAM) as mineral oil is a lot more pleasant to work with than DOT brake fluid, when it comes time to bleed your brakes (another delight).

I think a lot of the "stronger" commentary comes from disc brakes generally providing more braking for a given amount of hand effort compared to rim brakes.
Getting full braking on my road bike - with old, single-pivot Saccon rim brakes - takes literally a white-knuckle effort.
On my nice MTB, I can get all the braking I'd ever want from a moderate, 2-finger effort.
I'd say that calling disc brakes stronger - for the amount of hand effort that feels comfortable and natural to apply - is a quite fitting description for many bikes.

This is a massive thing that the anti disc crowd don't get, and it stays this way forever unlike cabled brakes which are susceptible to corrosion and dirt ingress making the brakes harder to operate. Yes modern rim brakes can be amazing (105 5800 and above) but it doesn't take much to change that.

09box, The greatest virtue is that disc brakes work better in wet conditions.

Braking power is limited by traction and a set of linear pull cantilever brakes or dual pivot caliper brakes modulate braking power well, while still capable of delivering enough power to endo the bike and rider.

Disc brakes wouldn't be a deciding factor for me WRT a new bike purchase.

Brad

Better braking in the wet
No rim damage from braking
Rims can be made stronger lighter and more aero

If you live in a dry climate all you're doing is adding a pound to your bike and restricting your wheel options.

I understand that the big reason for the thru-axle is to keep the front wheel from self-ejecting. I guess you should put that on the negative list for disc brakes.

That IS a consequence, which the bike industry would never admit to.


No, you should put that on the list of poor engineering decisions that the bike industry has accepted as standard.
It is not an unavoidable feature of disc brakes as such.

Putting the caliper on the front of the fork leg would have been a far better solution, not only to avoid wheel ejection but also for thru-axles.
As it is, you still have ride forces pushing the axle up, and brake forces pushing the axle down.
And as thru-axles aren't press-fit, the design still allows the axle to shift around and become self-loosening if the lever is ever not sufficiently tightened.

Oh man! Now I have to check to see how the front wheels of my Catrike are held on.

I can tell you from personal experience that the front wheel disc brakes have PLENTY of stopping power to lift the rear wheel off the ground. It won't endo, though, because the sprocket bash guard hits the ground to stop it. Might it eject a front wheel? I honestly don't know. I've never needed to take one of the front wheels off. If I have a puncture, I just roll the trike up on it's side.

Forks with solid "lawyer lips" are adequate security against front wheel ejection if the axle nuts or qr skewer are tightened properly. So the lack of a thru-axle isn't a hazard.

I understand the theory but I'm not 100% it works in real life.

I worked on a full suspension mountain bike from a major manufacturer that kept ejecting it's front wheel. The best solution I could come up with was to replace the QR lever with a genuine Shimano (enclosed mechanism) lever. It wasn't my bike and the owner never brought it back so I don't know if that was an adequate solution.

Some high dollar forks are not sold with lawyer tabs. Like say Enve IIRC.

I can see where disc brakes could be an advantage; in wet conditions, and for severe downhill speed limiting (either on long mountain descents, or on heavily loaded touring/tandem bikes). Other than that, I can't see where the extra weight, cost, and complexity would be worth it.