rick458

Looking through different vendor sights I see MTBs often have Disc brakes but far fewer road bikes, I thought Disc worked better esp in the wet

jimc101

They wern't allowed in racing, now the UCI has allowed them in Cyclocross, expect to see them becomming more common place on road bikes; when they are used in road racing, they will quickly filter through to the consumer market.

Remember that it's all weight in racing, additional wheels for the support crews to carry, will be interesting to see how it is done.

Also, there is the problem of fitting the reservior, but with DI2 (electronic shifting) or external placement this should become possible.

Would expect this and 135mm rear axle's to come in over the next 2-5 years.

For touring bikes with cable discs, these are now becming fairly common

Kimmo

Wet braking isn't too shabby with good old DPs.

Discs weigh more. They require beefed-up forks and stays, and a dished front wheel.

Discs make a lot more sense in muddy conditions, where rim brakes can cause excessive rim wear.

IMO discs will never be considered essential for elite road machines.

135mm rear hubs on the other hand, make a lot of sense.

jimc101

Agree with this, but money talks, and IF professional road cycling goes to disc, the tecnology will quickly come to the comsumer market, the weight thing is important as well, CF frames are now so light, some have to have weights added to get them to the minimum allowed weight, so adding a little for discs is not really an issue.

fietsbob

They appear on sporty commuting bikes already, those with a 622-32 to 40 tire capability.
then their inclusion in the build specs is all about foul weather braking, day after day
... raining for weeks on end. and snow sleet slush , etc.

Kimmo

I guess they're fractionally more reliable too, another commuter consideration

FBinNY 

Racing is about what makes bikes go, not what makes them stop. In competition braking is used for speed control, but serious stopping power isn't needed.

Caliper brakes are more than adequate to the requirements of racing, even in downpours and I'd be very surprised to see anyone take the weight penalty involved in a disc brake system, until those systems get much lighter and smaller.

safariofthemind

The weight penalty is small for mechanical disc brakes like Avid BB7's. I think they are coming to most road bikes - save for the most extreme racing models and the low end (cost considerations make canti's a better choice) within the next 5 years. Especially now that there are quite a few models proven reliable at reasonable prices.

Al1943

Unnecessary weight for a racing style bike.

Re-Cycle

Exactly what everyone else said about weight keeping disks out of road racing. Disk brakes require bulkier hubs for starters, that coupled with the disk itself would increase rotational weight which reduces your ability to accelerate.

at 160grams a pair I doubt you could find a disk setup that is even remotely as light

Shimagnolo

Lennard Zinn recently wrote an article in Velonews on testing of
carbon road wheels in braking while descending Flagstaff Mt.
What was news to me is that there are serious R&D issues with making
the braking surfaces of CF wheels hold up to the heat generated.
It requires special high-temp resins, and reinforced sidewalls to withstand the braking.
He pointed out that if road bikes went to disc brakes, it would enable cheaper, lighter CF wheels to be built.

Re-Cycle

Oh ya, and disk brake wheels have to be laced with consideration for the braking torque. As far as braking goes you can lace a rim brake wheel radially with as few spokes as you feel comfortable with and be fine. Not the case with disk.

jimc101

Only if hand build, with factory wheels, they can do just about anything, the Fulcrum Red Carbon XRP uses a non-3 cross pattern, if it computer designed, then it can be designed radial, carbon and a few spokes as they want. Can't see why even a Reynold RZR 46 couldn't be re-designed to take disc's if their sponsored teams demanded a ultralight weight carbon disc brake wheel.

If you were hand buiding a wheel for disc's can't see the difficulty in getting the lacing correct, I've put several disc wheels together, the instructions are avaliable in the Shimano Techdocs.

BCRider

Reduced and paired spoke wheels for disc brakes are certainly doable. But not full radial lacing. You can't use all radial for disc brakes for the same reasons you can't use all radial for drive wheels.

The use of super light carbon rims coupled with disc brakes to produce a wheel and brake combined weight that is the same as the current road wheels and caliper brakes would be just about the only reason for racing bikes to shift to disc brakes. Even if the weight only matched the disc brake wheels concentrates the weight in by the hub where it doesn't slow down the rotational acceleration as much. So just by shifting the mass from the rim to the hub there would be a nice advantage for sprinting compared to heavier rim brake style rims. But then there's the issue with the fleeting gains and losses from aerodynamics. A disc setup definetly has more draggy bits around the hub area. Perhaps shaped calipers that hide in a streamlined forward portion of the fork leg such that the fork and caliper form a streamlined teardrop shape?

As for real world bikes used for every day riding where fenders are not seen as some horrible contraption aimed at reducing sprint times and top speeds disc brakes are really nice. They offer an all weather performance for those of us living in wet areas that can't be beaten. As such we're seeing a large number of higher end hybrids, touring and cyclocross frames with disc tabs. And that's a nice thing to see.

Re-Cycle

This is news to me, I never heard of machine built wheels having any advantage over their hand built counterparts. Might want to check on that again.

Disadvantages to a disk road race configuration:

-Wheels require heavier spoking
-Hub needs more material
-Add a disk
-Longer cables
-Oh, and you can't just add disk tabs to a road fork / chain-stay, it has to be reinforced:


The part I'm curious about is machined vs non machined rims. If say an open pro rim came in both flavors, would the non machined version actually be lighter? If so I guess there is an argument that taking the weight from the outside of the wheel and placing it in the center is better.

Oh wait, we could remove the rear brake bridge, I'm sold on the disk idea now

HillRider

Weight will always be an issue for pure racing bikes even with the current UCI minimum. The very light weight frames and components that let builders create a sub 15 pound bike allow the teams to add power meters, and other useful items while still staying just above the mandated minimum weight. Heavier brakes will make this option not as useful.

Another problem is fast wheel changes are essential to a racer. Disc brakes will always impede wheel changes and that, alone, will disqualify them until a totally flat-proof tire system comes along.

jimc101

Modern Factory wheel, like Shimano, Fulcrum, ZIPP, DT etc are a world away from machine built wheels common on most low end bikes.

These factory wheels will be designed to be near enough perfect straight fom the box.

For that picture of a failed fork, that leg looks a little whimpy to begin with, as though the tabs were just put on a normal fork. Take the Salsa Vaya which has discs, it's far more substantial in the legs than that; when discs came to MTB, ppl didn't just weld tabs to old forks, new ones were made which were designed for the disc, and additional forces involved.

With all the CEN testing which bikes have to go through now, all the factors of where to add and remove weight / strength are taken care of by the design engineers who have to spec the frames.

For wheels needing heavier spokes, why? I have a SRAM 9.0SL disc with DT Revolution spokes on a Mavic 717, built it, and have run several hundred miles on & off road with no need to true.

safariofthemind

The thing is, only a tiny fraction of road bikes are pure racing machines. Most of the market (club riders, touring, randonneurs, commuting, CX, cruisers, etc) could benefit with a sturdy 20-25 lb bike with the improved braking of discs IMO.

motobecane69

i got a disc brake on the front of my touring framed commuter. I love it. i get road bike like speed riding around the city. I can stop without issue in all weather conditions (and I do commute in all weather) as well as keep my speed in check going down big hills. I remember the first time i took my bike down a serious hill last year where i hit over 40mph. I went to hit the front brake and it barely did a thing, it was pretty scary. I went down a similar hill with my commuter the other day and the disc brake is so much better for controlling speed.

I do agree with those who say we probably won't see it on true "racing bikes" but if your the type who has a road bike for your daily rider, club rides, century's etc. I don't see why people wouldn't opt for a disc brake.

LarDasse74

They could, but the current trend is relatively inexpensive bikes that look and sort of behave like thoroughbred racing machines at the expense of any versatility or usefulness.

coldfeet

The two major reasons are that that discs weigh more, an important consideration when you're trying to get the bike as light as possible, and MTBs experience bad conditions more often, for that, discs rule. I try to ride as much as possible in the Winter, and here that means foul slop with lots of grit, so I make sure anything i ride in the Winter has discs.

sillygolem

Alternatively, drum brakes still remain popular on cargo bikes because they allow for a wheel that isn't heavily dished, increasing overall strength. Since they're expected to be used in any weather (unless you're talking indoor industrial bikes) they use drum or disk brakes almost universally. Obviously, the weight penalty isn't a big deal.

relyt

Disc brakes are really overcomplicated and not necessary for most riders. Calipers stop bikes well enough.

FastJake

My thoughts exactly. Properly setup rim brakes will lock up either wheel at will, even in wet conditions. Disc brakes only make sense (to me) for mountain bikers who would otherwise destroy their rims if they didn't use disc brakes. The rest of the time discs just make the bike heavier and more complicated than it needs to be.

motobecane69

I somewhat disagree. I live in a relatively flat area, but I see guys on here posting videos of riding in mountains and the disc brake is far superior for scrubbing off speed on major descents. That is a MAJOR additional safety feature for avid recreational riders who do a lot of miles but will probably never be in an actual race.
When you look at cost of a higher end bike, its the same cost for a BB7 disc brake, even a little bit cheaper than it is for an ultegra brake caliper so for someone like me, I'd love the option of a disc brake on the front of my road bike.