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  1. #1
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    road bikes and disc brakes

    Why is it I don't see disc brakes on road bikes?

    Thanks,

    Jim

  2. #2
    Senior Member mulveyr's Avatar
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    Quote Originally Posted by jtdickie View Post
    Why is it I don't see disc brakes on road bikes?

    Thanks,

    Jim
    Not looking in the right place?

    More and more touring and utility bikes have them. But people who weigh components to fractions of grams would never tolerate the additional weight over caliper brakes.
    Knows the weight of my bike to the nearest 10 pounds.

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    Bike ≠ Car ≠ Ped. BarracksSi's Avatar
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    They're coming.

    Race bikes have already been loaded with ballast to meet the UCI-mandated minimum weight. Some people have said that it would make sense to put that extra weight to good use -- such as, say, disc brakes so they don't have to cook wheel rims on 50-mph downhills.

    I can't remember its name, but there's a new one with two small rotors on the front, giving plenty of braking force without adding any twisting forces to the fork.

  4. #4
    tsl
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    It's because they don't sell well.

    Trek debuted the Portland in 2006 as the first production road bike with disc brakes. They discontinued it due to poor sales after the 2011 model year.

    I don't have many pics of the non-drive side of mine (a 2006 model). Here's the only one I could find fairly quickly.



    Other than four-seasons all-weather commuters who are willing to drop some serious coin on a bike to ride in the rain and snow, there's no compelling need for disc brakes on a road bike.

    Part of it too is that dealers couldn't figure out how to sell them. I own the only one sold in my area. There are six Trek dealers just on my side of town. Five of them have never even seen one in real life, until I ride in the door, then we're instant celebrities. They all think it's cool, but they don't have a clue as to who they'd sell one to.
    Last edited by tsl; 09-25-11 at 09:56 PM.
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  5. #5
    tsl
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    Quote Originally Posted by BarracksSi View Post
    Race bikes have already been loaded with ballast to meet the UCI-mandated minimum weight. Some people have said that it would make sense to put that extra weight to good use -- such as, say, disc brakes so they don't have to cook wheel rims on 50-mph downhills.
    The problem with that argument is that the wheels weigh a ton, (well, okay, 2100 grams or so). Sure, disc brakes are nice on mountain descents, but you have to pedal the damned things up the mountain first.

    I've done it, so I know it can be done,

    but it was neither fun, nor pretty.

    Next time I go to Colorado, I'm taking my Litespeed with its 1400 gram wheelset.
    My two favorite things in life are libraries and bicycles. They both move people forward without wasting anything.
    The perfect day: Riding a bike to the library.—Peter Golkin


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  6. #6
    Senior Member Nermal's Avatar
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    BarracksSi, That's a problem I had never considered, and already there's a solution waiting to go.
    Some people are like a Slinky ... not really good for anything, but you still can't help but smile when you shove them down the stairs.

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    I've ridden in downpours and down mountains (Mt. Evans even) and have always found rim brakes good enough.
    Specialized Secteur & 29" Camber, 26" Trek MTB.

  8. #8
    Bike ≠ Car ≠ Ped. BarracksSi's Avatar
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  9. #9
    idc
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    Quote Originally Posted by BarracksSi View Post
    Nice. $1 per gram.

    The next bike I buy will probably be a CX with disc brakes. I have a good, light (enough) road bike for decently dry conditions but I've ridden through enough rain showers now to want something with disc brakes. Fortunately UCI has now legalized disc brakes for cyclo cross so more and more 2012+ models should come with disc brakes. And the CX will also double duty for the times I want to ride a bit of off-road.

  10. #10
    tsl
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    Quote Originally Posted by BarracksSi View Post
    That's claimed weight, not measured. And I doubt it includes rotors (and possibly not rim tape). Rotors count as rotating weight, just so you know. Mine are 120g each, plus let's say 5g each for the six mounting bolts and a drop of blue Loctite. So that's another 300 grams to your 1500 for 1800. Still nowhere near a "climbing" wheel.

    I don't see Alberto trading in his Zipps in the near future.
    Last edited by tsl; 09-26-11 at 09:33 AM.
    My two favorite things in life are libraries and bicycles. They both move people forward without wasting anything.
    The perfect day: Riding a bike to the library.—Peter Golkin


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  11. #11
    Bike ≠ Car ≠ Ped. BarracksSi's Avatar
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    All I'll want is for the Pro Tour to start using them. Then maybe us mortals will have more options available (not that the current offerings aren't good, 'cuz they are). I can't say that I'll give up my road bike anytime soon, but even after converting my commuter to drops -- which the general public perceives as a "road bike" -- I'd like to build up another that includes disc brakes.

    Why the pros? Well, where d'ya think they developed integrated shift/brake levers?

  12. #12
    Travelling hopefully chasm54's Avatar
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    As has been pointed out, it's not just the weight of the wheels, it's the forks. They need to be beefed up to withstand the strain, and that both adds more weight and compromises handling. And there really isn't any need for them, if you're riding on the road you don't get the crud that CX or mountain biking has to deal with, and my rim brakes work fine. Moreover, while discs certainly stop you, they also require more maintaining and are more vulnerable to damage. So for the moment I can't see that the pros outweigh the cons for road cycling.
    There have been many days when I haven't felt like riding, but there has never been a day when I was sorry I rode.

  13. #13
    Senior Member mulveyr's Avatar
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    Quote Originally Posted by chasm54 View Post
    Moreover, while discs certainly stop you, they also require more maintaining and are more vulnerable to damage. So for the moment I can't see that the pros outweigh the cons for road cycling.
    I see people claim this all the time about disc brakes, and I have no clue whatsoever about where this idea comes from.

    I have a touring bike with discs, and a road bike with dual-pivot calipers.

    When I do my yearly complete tear-downs that include brake maintenance, after I've taken them off and cleaned them, I can install, align, and adjust my disc brakes in literally less than five minutes.

    When I do my dual-pivots, it takes a good 15 minutes to get everything perfectly centered and aligned.

    When I need to change my disc pads, I drop the wheel, pull the retainer clip, install the new pads, back off the dial, and I'm done.

    When I need to change my dual-pivot pads, I need to deflate the tire, drop the wheel, install the new pads, fiddle with height and toe-in, tweak the barrel adjuster, reinstall and reinflate the wheel... and I'm done a lot later than the disc pads.
    Knows the weight of my bike to the nearest 10 pounds.

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    Travelling hopefully chasm54's Avatar
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    Quote Originally Posted by mulveyr View Post
    I see people claim this all the time about disc brakes, and I have no clue whatsoever about where this idea comes from.

    I have a touring bike with discs, and a road bike with dual-pivot calipers.

    When I do my yearly complete tear-downs that include brake maintenance, after I've taken them off and cleaned them, I can install, align, and adjust my disc brakes in literally less than five minutes.

    When I do my dual-pivots, it takes a good 15 minutes to get everything perfectly centered and aligned.

    When I need to change my disc pads, I drop the wheel, pull the retainer clip, install the new pads, back off the dial, and I'm done.

    When I need to change my dual-pivot pads, I need to deflate the tire, drop the wheel, install the new pads, fiddle with height and toe-in, tweak the barrel adjuster, reinstall and reinflate the wheel... and I'm done a lot later than the disc pads.
    Fair enough. I take it you don't bend any discs, then? And I've seen plenty of my MTB-ing friends struggling with jammed discs. But ymmv, and anyway I'm not arguing against discs for tourers, merely saying I don't see that they have any particular advantages for road bikes at present.
    There have been many days when I haven't felt like riding, but there has never been a day when I was sorry I rode.

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    Quote Originally Posted by tsl View Post
    Rotors count as rotating weight, just so you know.
    That weight is nearer the hub than the rim (and the axis is an important part of the "rotating weight" issue).

    This says that "inertial" (ie, rotational) weight of the wheels is negligible.

    http://www.biketechreview.com/review...el-performance

    I haven't seen any source that indicates to what amount the rotation weight contributes to effort expended moving the bike.
    Last edited by njkayaker; 09-26-11 at 11:48 AM.

  16. #16
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    I have disc brakes on my touring bike and love them. I have no need for speed, however, so weight isn't an issue with me. I understand why roadies don't like them as the extra weight would definately slow down a good cyclist (however most aren't good enough to notice the weight difference, but that's a topic for another thread...).
    "There are many causes worth dying for. There are none worth killing for." Albert Camus

  17. #17
    tsl
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    Quote Originally Posted by njkayaker View Post
    That weight is nearer the hub than the rim (and the axis is an important part of the "rotating weight" issue).

    This says that "inertial" (ie, rotational) weight of the wheels is negligible.

    http://www.biketechreview.com/review...el-performance

    I haven't seen any source that indicates to what amount the rotation weight contributes to effort expended moving the bike.
    Not saying it does or it doesn't. Just saying it's not reasonable to compare one set of wheels with a braking surface to another set without.

    Unless the second one is a fixie.

    Since you can't remove the braking surface from a set of rim brake wheels for a valid comparison, then you must add the braking surface--the rotors--to the disc brake wheelset for a valid, apples to apples comparison. Anything else is disingenuous.
    My two favorite things in life are libraries and bicycles. They both move people forward without wasting anything.
    The perfect day: Riding a bike to the library.—Peter Golkin


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  18. #18
    Senior Member Thor29's Avatar
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    There's at least one company betting that discs on road bikes are worth doing: http://www.volagi.com
    The only thing I don't like about the Volagi is that it has 130mm spacing. That really limits the number of hubs you can use on the rear.
    I have a Salsa La Cruz cyclocross bike with disc brakes. I really like the extra stopping power. I personally would like to see a lighter version of the BB7 brakes and more options for road frames that use disc brakes.

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    Senior Member Thor29's Avatar
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    Quote Originally Posted by chasm54 View Post
    Fair enough. I take it you don't bend any discs, then? And I've seen plenty of my MTB-ing friends struggling with jammed discs. But ymmv, and anyway I'm not arguing against discs for tourers, merely saying I don't see that they have any particular advantages for road bikes at present.
    I also ride mountain bikes and so far nobody in my group has ever managed to bend a rotor. Bending rims happens sometimes, which makes disc brakes an even better option since you don't have to worry about a bent rim hitting the brake pads. (I once tried to ride my Surly Cross Check on a mountain bike trail and bent the rear rim so severely that I had to disconnect the rear brake to finish the ride).

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    Quote Originally Posted by chasm54 View Post
    As has been pointed out, it's not just the weight of the wheels, it's the forks. They need to be beefed up to withstand the strain, and that both adds more weight and compromises handling. And there really isn't any need for them, if you're riding on the road you don't get the crud that CX or mountain biking has to deal with, and my rim brakes work fine. Moreover, while discs certainly stop you, they also require more maintaining and are more vulnerable to damage. So for the moment I can't see that the pros outweigh the cons for road cycling.
    There are some advantages for racers: the rim doesn't need to withstand the heat or abrasion of the brakes, which are big problems with plastic rims. That, in theory, should let the rims be a bit lighter, and longer lasting. Theres' also the possibility of some (very small, I suspect, but that doesn't matter to the people who buy this stuff) aerodynamic improvement from not having to have a brake track.

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    Quote Originally Posted by mulveyr View Post
    When I need to change my disc pads, I drop the wheel, pull the retainer clip, install the new pads, back off the dial, and I'm done.

    When I need to change my dual-pivot pads, I need to deflate the tire, drop the wheel, install the new pads, fiddle with height and toe-in, tweak the barrel adjuster, reinstall and reinflate the wheel... and I'm done a lot later than the disc pads.
    I'm a little puzzled. When I replace my sidepull brake pads I just screw in the barrel adjuster, take off the old pads, attach the new pads, and I'm done. I don't see the need to do any fiddling with the wheel or tire.

    The main maintenance problem I see with rim brakes is that they eventually wear down the rim surface and replacing the rim takes a significant amount of time. Since I live in a climate where we have a limited rainy season this is only needed every 50 - 80 kmiles and therefore isn't a major burden. But I'd welcome a switch to a separate (and easier to change) disc if I frequently rode in wet conditions that wear out the rim's braking surface. I'd opt for just having the disc in the front since that's where you need the most effective braking and retain the lighter rim brake in the rear (I have yet to wear out the brake surface on a rear rim).

    One other consideration is that the current disc brake designs make the 'lawyer lip' retention of the front wheel an essential feature. With a front rim brake I prefer to remove the lawyer lips to provide for more convenient wheel removal and replacement.

  22. #22
    coprolite fietsbob's Avatar
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    Yea there are road bikes for racers .. weight weenies ... Titanium and carbon-fiber land.

    then there are road bikes for commuters and the rest of the Lumpen Proletariat .
    Put the BB up a half inch or so and you got the Cross bike thing going on too .

    something for just about everyone.

    FWIW, On my V brake posts I have Magura hydraulic rim brakes , pad changes are literally a snap.

  23. #23
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    Thanks all for your input.

    Jim

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    Bike ≠ Car ≠ Ped. BarracksSi's Avatar
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    Quote Originally Posted by dscheidt View Post
    Theres' also the possibility of some (very small, I suspect, but that doesn't matter to the people who buy this stuff) aerodynamic improvement from not having to have a brake track.
    Although I think it's silly, not only does Zipp put little dimples in their wheels, they even sell tires with dimples on them. I'll bet that they'd love to dispense with the brake track altogether.

  25. #25
    PatronSaintOfDiscBrakes dynaryder's Avatar
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    Quote Originally Posted by chasm54 View Post
    Fair enough. I take it you don't bend any discs, then? And I've seen plenty of my MTB-ing friends struggling with jammed discs.
    Apples to oranges. MTBing causes all kinds of damage you don't regularly see on street bikes. When was the last time you bent a hanger on a rock?

    I've had to straighten the discs on two bikes;one got damaged in shipping from eBay(wheel also needed trueing) and one took a hit playing bike polo. Never had an issue just riding around town.

    C'dale BBU('05 and '09)/Super Six/Hooligan8and 3,Kona Dew Deluxe,Novara Buzz/Safari,Surly Big Dummy,Marin Pt Reyes/Novato,Giant Defy 1,Schwinn DBX SuperSport/Qualifier,Brompton S6L,Dahon Speed Pro TT

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