I find it a bit hard to believe that disk brakes have heat problems for road race bikes on long descents. Most tandems use disks and tandems need way more braking than a single. And, tandems use disks because the braking effort creates so much heat using rim brakes that the tires can explode (this has happened to me twice - a bit scary). If road singles required braking effort that is too much for a disk, they should also generate enough heat with rim brakes that tires blow up, but I do not think that is a problem.
I have not seen the article James references and I do not follow road bike tech, so I may be missing something, but it seems if disks will work for tandems they will work for singles.
Joined: 07 Dec 2004 Posts: 1259 Location: da 'Ville
Posted: Fri Apr 27, 2012 1:50 pm Post subject:
freeheelwilly wrote:
Aren't they a solution in search of a problem?
Nope. Disc brakes on roadies are going to go big. The problem it solves is that of rim brakes overheating carbon rims (resulting in major brake fade for one thing, and beyhond that, tire, and even rim failure). They do not dissapate the heat nearly as well as aluminum.
With aluminum rims, it is a solution in search of a problem. Not so with carbon rims, which are becoming wildly popular. This despite potential braking issues - only a problem on the longest, steepest descents, so most folks will never have a problem. Seeing as how I live at the foot of the Rockies, and as how dire the potential outcome could be...I will eschew any and all carbon rims until the issue is solved (most likely by roadie discs - which means a new frame, which means I'll probably be waiting even longer, since I just bought a new frame).
I've not heard of the issue of disc brakes failing due to heat. Seems unlikely, given the punishment DH mtb's give their brakes. But maybe the issue is making them robust enough while remaining roadie-light. Seems like the engineers in question will nail this before long though, assuming it's a real issue.
EDIT: Well, that bikerumor.com link (posted while I was typing) certainlhy answers the question of whether roadie discs have failure issues! Sounds like they are more sketchy than rim brakes on carbon rims, for sure. While I've got carbon-almost-everything on my ride, I'll be sticking with alloy rims and rim brakes. _________________ Control is never achieved when sought after directly. It is the surprising outcome of letting go.
Joined: 07 Dec 2004 Posts: 1259 Location: da 'Ville
Posted: Fri Apr 27, 2012 2:01 pm Post subject:
twopass wrote:
Wow, nice ride! Positively pimpin'!!!
(but now I have to wonder about the disc brakes, of course) _________________ Control is never achieved when sought after directly. It is the surprising outcome of letting go.
Most tandems use disks and tandems need way more braking than a single. And, tandems use disks because the braking effort creates so much heat using rim brakes that the tires can explode (this has happened to me twice - a bit scary)
Don't most tandems use MTB disks, even disks specifically designed for downhill mtbs?
If so, multiple pistons, big calipers, and huge diameter + thick rotors mean they can stand the heat.
I believe the disk brakes being put on road bikes are designed to be a lot lighter, hence not as efficient at dissipating heat.
edit: I've also heard of loaded-touring tandems using a drum brake hub (??), that they use as a "drag" brake on long descents, to save their disk brakes from over heating. this might be an ancient setup though, been awhile since I've looked into it...
Joined: 24 Jan 2005 Posts: 7012 Location: Castle Rock, CO
Posted: Fri Apr 27, 2012 2:24 pm Post subject:
skizix wrote:
Seeing as how I live at the foot of the Rockies, and as how dire the potential outcome could be...I will eschew any and all carbon rims until the issue is solved (most likely by roadie discs - which means a new frame, which means I'll probably be waiting even longer, since I just bought a new frame).
When was the last time you road a carbon rim. I ride long descents up to 50 mph all the time and have been on carbon rims both tubular and clincher for a few years now with little problem.
The resin and brake tracks have come a long way in the last few years. You can't be stupid with the brakes and you will go through more pads.
Zipp, Enve and Reynolds all have solid carbon clinchers on the market today.
Thanks for the link James. Looks like the issue is not that disks cannot handle the braking load - and heat - of road bikes, but that a disk brake that can do that is too heavy. I put this in the "too heavy" bucket, not the "fail due to load" category, but I see the point either way.
Carbo, tandems can use a rear drum brake; mine does. However, this technology has been replaced by disks which are lighter (mine tandem is old). Either a drum or disk can be set up on the rear as a drag. My tandem uses regular cantis and bake levers, and has a rear drum rigged to a mountain bike thumb gear shifter that can be put on as a drag. I retrofitted this after blowing a rear tire at speed on a long fast descent. I blew another tire when I foolishly thought I did not need the drag.
Joined: 20 Oct 2005 Posts: 17876 Location: following Diogenes, but the ba$tard threw away the lamp so I'm just stumbling along in the dark!
Posted: Fri Apr 27, 2012 5:10 pm Post subject:
Anti-stoke!
a hit-and-run two-fer...
I hope justice is very harsh on that motorist! _________________ "Moderate is not the new Low" - Chris Joosen, USFS Lead Snow Ranger (Tuckerman Ravine, White Mountains National Forest)
Joined: 21 Dec 2004 Posts: 240 Location: Back in the Bay Area
Posted: Sat Apr 28, 2012 1:39 am Post subject:
That neighborhood seems, as far as I've experienced during the past twenty-something years of riding there, to have a decidedly anti-bike anti-stoke. Partly, I assume, because we cyclists act pretty brazen and bold in the bay area, and partly due to the unrivaled sense of entitlement many folks have around these parts. This, coupled with rats-in-a-cage general crowdiness and urban angst, gets us to the video.
What's kinda gnar is the commentary that follows in Youtube. It's so wild how two wheels brings out the vigilante in folks. It's nuts.
I'm a cyclist and motorcycle commuter and the hate for two wheelers always gives me pause. I'm down with irrational hate - I feel it for all kinds of things all the time; poor planning, lack of common sense, stupidity, laziness, greed, etc. All things I hate. But why the hate to two wheels?
That neighborhood seems, as far as I've experienced during the past twenty-something years of riding there, to have a decidedly anti-bike anti-stoke. Partly, I assume, because we cyclists act pretty brazen and bold in the bay area, and partly due to the unrivaled sense of entitlement many folks have around these parts. This, coupled with rats-in-a-cage general crowdiness and urban angst, gets us to the video.
the Bay Area self-entitled douche sphere has ratcheted up the game quite a bit recently. Nothing about anti-bike most of the dickbags would probably spew pro-bike. It's just they are assholes. Nothing more, nothing less.
Joined: 04 Jan 2005 Posts: 887 Location: Eugene, OR
Posted: Sat Apr 28, 2012 2:56 am Post subject:
twopass wrote:
Yes, that Colnago is hot, must have the new Campy electric set up...Wow! I'm also loving that awesome chrome bike stand, plus it's the only thing in the picture I could afford
The video sucks, fu_king phones and texting while driving, and on a curvy and narrow road. I have to think that it was not an intentional hit, that would be hard to believe.
Also, stop at the signs!!!! _________________ Those voices in your head are not real, but they have some really great ideas!
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