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Thread: disc brakes on road bikes - why not?

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    Default disc brakes on road bikes - why not?

    just askin'........sorts gonna segue off the EBB/disc commuter thread. got this from a client:..............:) Hey Steve, Just chillin' over here in Singapore! I love my coco - it's been racking up the k-metres - up to 2500 already! I just had a superbly suffering foray into Malaysia on Saturday - 225k in just under 8 hours - lots of hills, traffic and punishing heat - a great day!

    A nugget for your knowledge bin - I ride in the mornings mainly - in the dark before work. A couple weeks ago I got caught out in a thunderstorm with two mates in the backcountry of Singapore (it does exist). It was about 6am with no light and there were branches down everywhere. We're ticking along at 30kh with me in the middle and I hear "BRANCH" - just as it hits my front wheel... The bike washed out from under me and I was sent hurtling towards a concrete drainage ditch. With no time to think instinct took over and I pushed the bike towards the ditch to break my advance. My beloved coco crumpled into the ditch while I skidded (relatively) harmlessly into a patch of grass. After shaking off my state of shock, and taking compliments from the rider behind me for cordially crashing out of his way, I went to pull my trusty machine from the jaws of ruin.

    Guess what? NOT A SCRATCH! I did a quick and thorough inspection, she was indeed rideworthy, even shifting perfectly, and hopped on to complete the last 30k of my morning ride. That evening I went over her completely, even removing the fork to inspect for cracks, nothing. What damage there was was inconsequential, a little torn bar tape and small rip on the seat. And oh, the rear wheel was a bit out-a-whack (thanks to the disk brake this was not even noticed on the ride home).

    Just want to say THANKS again for this bomb-proof masterpiece, I get nothing but salivating looks from the rest of the guys (and gals) on my group rides. ............:) please discuss..........Steve.
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    Steve Garro, Coconino Cycles.
    Frames & Bicycles built to measure and Custom wheels
    Hecho en Flagstaff, Arizona desde 2003
    www.coconinocycles.com
    www.coconinocycles.blogspot.com

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    Send me a frame to test out. I'll give you my measurements. I'll build it up with some nice fancy wheels and report back to everyone here.

    Sounds good?
    :cheers:


    -Eric
     

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    I like that bike. A little unorthodox, but it still looks right. Refresh us with the details on the build. IIRC you were sweating the detail stuff on that one.
     

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    Good enough for cars, motorcycles and mountain bikes....why not road bikes then? I do hear a lot about braking issues with carbon rims, this would solve that potentially, just again the whole weight/complication issue: hubs have to accept rotors, frame and forks have to accept calipers, and cable routing become an issue especially if you have hydraulics (then the whole issue of brake lever/shifter design to accept hydraulics, though you could stick to cable actuated ones)
     

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    What is the weight difference?
     

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    Quote Originally Posted by Flux View Post
    the rim makes a sweet disc brake.

    cheers,
    flux
    yeah- freaking 28" rotors. how can you beat that?
     

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    Quote Originally Posted by riceburner View Post
    Good enough for cars, motorcycles and mountain bikes....why not road bikes then? I do hear a lot about braking issues with carbon rims, this would solve that potentially
    see, that's what i'm talking about. i bet you could make a really light all carbon tubular rim - no heat issues from extended braking messing with the sewup glue either........discs calipers & rotor diameters could be slimmed down allot as they only have to slow down a skinny tire........cable accuated would be fine. if you have never tried discs then you don't realise how much superior they are in wet conditions. wheel out of true? *no big deal* as long as it doesn't hit the frame! faster descents with better braking? you bet. cable routing? same-same. if you can accept the idea of BB30 & electronic shifting, why be so quick to poo-poo discs? MTB phobia? Steve.
    Steve Garro, Coconino Cycles.
    Frames & Bicycles built to measure and Custom wheels
    Hecho en Flagstaff, Arizona desde 2003
    www.coconinocycles.com
    www.coconinocycles.blogspot.com

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    Quote Originally Posted by jerk View Post
    yeah- freaking 28" rotors. how can you beat that?
    pretty easily when they are anything but perfect - carbon braking surfaces, wet conditions, heat fade, tire rub if not perfectly true, and how about worn through sidewalls? let's not play the "because UCI says no" card. let's just ask "why not?" what if you could make the rims lighter reducing rotational weight, and move the brake weight lower to the ground? minimal diff, i know..........but so is the difference between a BB30 setup & a "regular" crankset.........why be pro-evolution in all aspects of road bike tech except braking? have you tried some nice discs? just askin'.......Steve.
    Steve Garro, Coconino Cycles.
    Frames & Bicycles built to measure and Custom wheels
    Hecho en Flagstaff, Arizona desde 2003
    www.coconinocycles.com
    www.coconinocycles.blogspot.com

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    i saw a guy up in greenwich riding a very swank road bike equipped with disk brakes. the thing looked very cool.

    some logistical questions: where is the reservoir kept, will campy/shimano/sram road "brifters" provide enough oomph, how do you reinforce a carbon fork to accomodate a bracket (or does the fork have to be steel), etc. etc.

    that black bike with the discs looks sweet!
     

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    love the stopping power of discs on my mountain bike, but I really dislike setting them up and dealing with slightly warped rotors.
     

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    Quote Originally Posted by 54ny77 View Post
    i saw a guy up in greenwich riding a very swank road bike equipped with disk brakes. the thing looked very cool.

    some logistical questions: where is the reservoir kept, will campy/shimano/sram road "brifters" provide enough oomph, how do you reinforce a carbon fork to accomodate a bracket (or does the fork have to be steel), etc. etc.

    that black bike with the discs looks sweet!
    that bike has Avid BB-7 mechanical discs - cable accuated. just sting them up to your regular levers.......that is a carbon fork.........Steve.
    Steve Garro, Coconino Cycles.
    Frames & Bicycles built to measure and Custom wheels
    Hecho en Flagstaff, Arizona desde 2003
    www.coconinocycles.com
    www.coconinocycles.blogspot.com

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    Default Honestly,

    I like the idea...I have been dreaming of a little campy caliper and 3 inch rotor for a long time. Road bike brakes generally suck, but they suck for a specific reason: the problem is racing. No one wants to be around the guy/ma'am that keeps grabbing a handful. Disks would make you have to be VERY careful when riding in a pack.

    I think someone just needs to make it. Retrofit to a campy lever, there's room in there for more stuff. That new little elf-shoe thing can be a reservoir.
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    cable-actuated discs? holy smokes i need to get out of the dark ages....who knew?

    (seriously, didn't know such things existed! i'm completely ignorant of cross and/or mountain bike technology...)

    Quote Originally Posted by steve garro View Post
    that bike has Avid BB-7 mechanical discs - cable accuated. just sting them up to your regular levers.......that is a carbon fork.........Steve.
     

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    I like it! You could have the reservoir be cleverly designed (and shaped) to face the interior of the brake/bars (i.e., it sticks out an inch or two to the left for the right lever and to the right for the left lever). Further, it could be shaped to provide an additional place to rest your hands. Does that make sense?

    Quote Originally Posted by huckleberry View Post
    I like the idea...I have been dreaming of a little campy caliper and 3 inch rotor for a long time. Road bike brakes generally suck, but they suck for a specific reason: the problem is racing. No one wants to be around the guy/ma'am that keeps grabbing a handful. Disks would make you have to be VERY careful when riding in a pack.

    I think someone just needs to make it. Retrofit to a campy lever, there's room in there for more stuff. That new little elf-shoe thing can be a reservoir.
     

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    IMO one of the real issues is that of braking torque and spoke tension.

    With a rim brake you are stopping the rim which then in turn stops the bike. With a disc you stop the hub which then transfers the torque from the hub to the rim through the spokes. This means radial spoke patterns are out and for the best wheel stabilty low spoke counts are also out. You can generate MUCH more braking force torque that you could ever do with chain drive torque and you risk spoke or rim failure if you don't use enough spokes.

    Most everything in the motorosport world has moved away from spoked wheels in part because of this.

    I agree with the Jerkman......... 26" discs are huge and powerful and offer great modulation and heat sink capacity.

    Discs do look cool though.

    dave
    D. Kirk
    Kirk Frameworks Co.
    www.kirkframeworks.com


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    Why did you have to bring logic into this discussion?

    Isn't this the land of make believe?

    :D

    Quote Originally Posted by Dave Kirk View Post
    IMO one of the real issues is that of braking torque and spoke tension.

    With a rim brake you are stopping the rim which then in turn stops the bike. With a disc you stop the hub which then transfers the torque from the hub to the rim through the spokes. This means radial spoke patterns are out and for the best wheel stabilty low spoke counts are also out. You can generate MUCH more braking force torque that you could ever do with chain drive torque and you risk spoke or rim failure if you don't use enough spokes.

    Most everything in the motorosport world has moved away from spoked wheels in part because of this.

    I agree with the Jerkman......... 26" discs are huge and powerful and offer great modulation and heat sink capacity.

    Discs do look cool though.

    dave
     

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    Quote Originally Posted by Dave Kirk View Post
    IMO one of the real issues is that of braking torque and spoke tension.

    With a rim brake you are stopping the rim which then in turn stops the bike. With a disc you stop the hub which then transfers the torque from the hub to the rim through the spokes. This means radial spoke patterns are out and for the best wheel stabilty low spoke counts are also out. You can generate MUCH more braking force torque that you could ever do with chain drive torque and you risk spoke or rim failure if you don't use enough spokes.

    Most everything in the motorosport world has moved away from spoked wheels in part because of this.

    I agree with the Jerkman......... 26" discs are huge and powerful and offer great modulation and heat sink capacity.

    Discs do look cool though.

    dave
    I have wondered about this issue before; if the braking forces would be different at the hub as opposed to the rim.. Thanks Dave for sharing some tech knowledge on it!

    Steve- regardless, I think this will be explored more and the issues resolved somehow. Your bike looks great as usual.

    Scott
     

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    Quote Originally Posted by Dave Kirk View Post
    IMO one of the real issues is that of braking torque and spoke tension.

    With a rim brake you are stopping the rim which then in turn stops the bike. With a disc you stop the hub which then transfers the torque from the hub to the rim through the spokes. This means radial spoke patterns are out and for the best wheel stabilty low spoke counts are also out. You can generate MUCH more braking force torque that you could ever do with chain drive torque and you risk spoke or rim failure if you don't use enough spokes.

    Most everything in the motorosport world has moved away from spoked wheels in part because of this.
    Are we know talking about Lightweights as wheels for disc brakes?
     

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    time to bring back the aerospoke....
     

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    Default these are "crossed"...

    Quote Originally Posted by Dave Kirk View Post
    This means radial spoke patterns are out and for the best wheel stabilty low spoke counts are also out.
    These are not radial.

    I am J-B Welding a rotor mount on one right now.

    Plus, you can "true" the rear wheel with those little twisty things. That comes in handy after you ram it into a rock, or root or sidewalk or whatever.
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