Author Topic: Re: Road bike disk brakes  (Read 122 times)

jim-ratliff

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Re: Road bike disk brakes
« on: July 02, 2013, 12:38:55 pm »

a very interesting article about the challenges facing road bike disk brakes. i still think they are coming.

http://velonews.competitor.com/2012/08/bikes-and-tech/technical-faq/technical-faq-throwing-ice-water-on-road-disc-brakes_235280
Less than a year later, and SRAM has introduced disk brakes for road bikes (and cross) and also has hydraulic rim brakes that are being used in this year's Tour de France.  Shimano is supposed to be releasing their disk brakes in the fall and borrowing cooling fin technology from their mountain bike rotors (that have extra cooling fins in the center of the rotor).

Sounds like there would actually be disk brakes in the le Tour if they were approved by whomever the sanctioning body is

.
http://velonews.competitor.com/2013/07/bikes-and-tech/news/shimano-unveis-6780-di2-hydraulic-road-brakes_292856
« Last Edit: July 02, 2013, 12:48:12 pm by jim-ratliff »
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Svend

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Re: Road bike disk brakes
« Reply #1 on: July 02, 2013, 09:26:03 pm »
Hey Jim,

Nice to be chatting about bike stuff again.  One of my favourite subjects, next to ski talk.

Before I go on, let me preface this by stating that I am no expert on road bike technology.  I have never owned a road bike, but have learned a few of the basics lately in assisting my brother search for a new road bike for himself. 

That said, the article by Zinn raises some very valid points re. weight and stresses on the hub and spokes.  The recent trend to low spoke count radial laced front road wheels being the most pertinent example, in my opinion.  I just can't see a lightweight wheel that is laced in that way being able to withstand the force of a hub-mounted brake when asked to stop a 220 lb rider hurtling at breakneck speed down a long steep hill. 

OTOH, if there is a market for this, and given that the manufacturers then WILL adapt the wheel designs to cope with disk brakes (a no-brainer based on years of mtn. bike experience), my guess is that the real-world performance of wheelsets may actually improve the overall performance of the bikes.  With proven performance gains, even weight-conscious riders may be swung in this direction.  What I'm getting at is this:  the wheels will have to be stiffer and stronger when built for disk brakes, and therefore they will also perform better.  Snappier acceleration, less flex, better steering and handling.

As an aside, I have heard that most modern wheelsets put as stock factory spec on road bikes today, are designed to perform well for riders of 160 lbs or less.  Light rims, low spoke count, radial lacing, thin spokes, light hubs (if that makes a difference).  A guy my size will probably never get good performance from a wheel like that (maybe I'm wrong on that, but it just makes sense to me).  The bike will feel like a noodle, no matter how good the frame is.

My experience, albeit with mtn. bikes, has been that some heavier bikes may actually perform better than lighter ones because their frames and wheels are stronger and stiffer, and there is much less energy wasted due to frame and wheel flex.  These performance improvements negate any losses due to extra weight.  Good geometry helps, of course, but I think you get the drift....

As a general comment, I think the whole lighter-is-better thing is highly overrated.  I know guys who agonize over 100g here and there, and spend big bucks to shave off these minor amounts from their rides.  And then they don't blink at carrying 1000g of water into their two bottle cages.  ???

So, do I think disc brakes for road bikes is a good thing? Not sure on that one, as I don't road ride, so don't know how good a high quality side-pull caliper brake can be.  Specifically, how strong the braking force is for, say, large riders going downhill fast (to use the above example). Or how good their performance is in wet weather.  Or in winter for that matter.  I can imagine that disc brakes may hold strong appeal to those riders living in rainy climates, or who ride even when the snow flies.  Urban cyclists will likely go for this in a big way, and we're seeing more and more hybrid bikes aimed at city riders with disc brakes.

The first time I rode a mountain bike with disc brakes I was blown away by how strong they were -- just a touch of the lever, and Bam! the bike stopped dead.  Took some getting used to.  But that is not what impressed me most, as my old cantilever rim brakes were always able to hold me, even on the steepest slopes.  Just needed good pads and lots of mustard on the levers, and they were plenty strong....if it was dry....  But when things got wet, and especially when mud got on the rims (a frequent happening), then they just plain sucked.  Not to mention leaves getting pulled up and stuck between pad and rim....yikes! Enter disc brakes....problem solved.  To me, that was their no. 1 advantage, was consistent performance in wet and muddy conditions. 

It'll be interesting to see how this evolves for road bikes.  Probably not the thing for many riders, but for some it will be a welcome improvement.

Cheers,
Svend

PS - nice to have the forum up and running again.
« Last Edit: August 01, 2013, 09:54:29 am by Svend »

jim-ratliff

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Re: Road bike disk brakes
« Reply #2 on: July 02, 2013, 11:12:02 pm »
An additional impetus may be carbon wheels with their requirement for special pads and an inability to dissipate heat very well. I would say that more than half of the good bikers I see in Central Park are running aero carbon wheels this year. It will be interesting to see how long before the high end components actually trickle down to bikes I can afford.

Like you, I am just blown away by the power and modulation of MTB disc brakes; and I do have low spoke count wheels on both road and mountain bike with no problems, but I am lighter as you said.  Here again, carbon may be an answer.  The guy at Neuvation now offers a 2 year warranty on his carbon wheels because of great experience with strength and reliability.  Not a single **** rim or pulled out spoke in the past two years.  They used to be more brittle, I believe.

The SRAM adaptatin of hydro power with rim brakes is an intriguing approach.

And I have to say that my bikes both ride better since I took about 10 pounds of weight off of the bike-rider combo.  For the first time, I can actually keep up with Lynn this year.
« Last Edit: July 03, 2013, 12:16:50 am by jim-ratliff »
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ToddW

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Re: Road bike disk brakes
« Reply #3 on: July 03, 2013, 03:46:22 pm »

 Specifically, how strong the braking force is for, say, large riders going downhill fast (to use the above example). Or how good their performance is in wet weather. 

In my limited experience (Ultegra 6700) brake technology improvement would be a plus for larger riders on hills ... especially steep hills that end in a stop sign  :o

ToddW

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Re: Road bike disk brakes
« Reply #4 on: July 03, 2013, 04:00:52 pm »
And I have to say that my bikes both ride better since I took about 10 pounds of weight off of the bike-rider combo.  For the first time, I can actually keep up with Lynn this year.

  Way to go Jim ... cutting your load and  slimming your form factor to reduce the drafting advantage that Lynn gets off you.  Don't forget to let her win occasionally  ;)

jim-ratliff

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Re: Road bike disk brakes
« Reply #5 on: July 03, 2013, 08:14:51 pm »
Todd:

I would recommend a set of KoolStop pads (the Salmon colored ones).  I replaced my Ultegra pads with these and they stop better, modulate better, and seem to wear on the wheel less.
And while they aren't always cleaning the rim as is the case with disk brakes, I've never noticed any problems on wetter rides, but my experience is limited to light showers and water left on the road after a shower.

http://www.koolstop.com

http://www.performancebike.com/webapp/wcs/stores/servlet/SearchDisplay?searchTerm=kool+stop&catalogId=10551&langId=-1&storeId=10052&ddkey=http:PBSearchTermAssocia tionsCmd

Jim
« Last Edit: July 04, 2013, 04:24:06 am by jim-ratliff »
"If you're gonna play the game boy, ya gotta learn to play it right."