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 Post subject: Disc brakes road bikes
PostPosted: Tue Feb 14, 2012 8:35 pm 
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Joined: Mon Sep 19, 2011 5:36 pm
Posts: 53
Location: Boston MA USA
They're coming, so no surprises there. I just read this article and it, honestly, scared me a bit. Having never actually thought about the differences in braking profiles in road, mountain biking, and cyclocross, I've simply thought of discs being an inevitability in just a few years time, likely about the time I purchase my next bike. Reading this, it seems that the braking loads of a road bike are significantly more problematic than I had imagined.

The TL;DR version of the article was that road braking loads are light load for long periods of time (long downhills), while both for mountain and 'cross, they're short and grabby. The road loads bring on brake fade, as all the components are too small to effectively cool quick enough, while mountain and cross doesn't brake long enough to build up enough heat to cause problems.

In any case, I'm curious of other peoples thoughts are on this. I've never had too little power from even inexpensive/cheap brakes (SRAM Apex and crappy ten year old Tektros). Modulation has always been sufficient for me: I'm not very picky here. Mind you, I'm not particularly heavy (160lbs/72kg), and use only aluminum rims.

I've seen a number of threads lately that partially address this (specifically the SRAM 2012 Red thread), but nothing particularly definitive. Hopefully this thread could be a clearinghouse on the topic.


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 Post subject: Disc brakes road bikes
Posted: Tue Feb 14, 2012 8:35 pm 


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PostPosted: Tue Feb 14, 2012 9:28 pm 
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Joined: Tue Nov 11, 2003 9:47 pm
Posts: 1733
Location: Santa Cruz, California, USA
500g more (when you include wheel frame and fork changes) pretty much kills it for me.

I also descend steep technical roads like the one that the BikeRumor guy crashed on. I'm a reasonably good descender, don't weigh much and know how to brake, but the parts will need to work 100% of the time for heavy riders who are not confident descenders and ride the brakes all the way down the ugliest possible descent. On a hot day. I have seen riders in the Death Ride doing this on perfectly straight roads that aren't even steep. Some people are just scared to go more than 25 mph on a bike. The discs have to work for them too. If production systems have a couple failures like this one you can say "class action lawsuit".

So I think what we'll see will be over engineered parts that work for everyone. Thick 160m or 180mm rotors, heavier calipers, etc. No WW parts from the MTB bin. That's great in that I don't want to see people crash, but it means that it will take even longer for disc bikes to equal the weight of caliper brake bikes, if they ever do. I don't see it ever happening to be honest.

I'd consider a disc bike for a dedicated rain bike but my rain bike's calipers work fine for me and I rode in the rain a lot last year.


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PostPosted: Tue Feb 14, 2012 10:17 pm 
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Posts: 377
Don't want to sound like a caveman (in fact I just ordered my Campagnolo EPS) but I can't see a place for them.

1) I get the weight saving at the rim benefit (potentially), but you will need more spokes to cope with the stresses which will offset the benefit, as will the reinforcement of the forks and non drive side stays to cope with the disc forces.

2) Even the rim weight saving may not be as much as you think as there will still need to be a rim bed suitably reinforced to take a clincher or tubular. Look at an Ambrosio Nemesis. The rim couldn't be any shallower and still have enough depth for a spoke nipple. Now factor this into something carbon. Not much less material in reality.

3) The weight of the caliper, disc and hydraulic lever will certainly be more than a mechanical equivalent.

4) Weight aside, wheels changes in a race will be a nightmare of spacing which will need to be overcome. Not so much of a problem to recreational cyclists, but the market is ultimately driven by the trickle down of what the pros use. The 2 mainstream discipline using discs (mtb and cx) don't have wheel changes for punctures, they rely on either a repair or pit stop, so not an issue.


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PostPosted: Tue Feb 14, 2012 11:05 pm 
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Joined: Fri Oct 28, 2011 3:25 am
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Location: United Kingdom of Great Britain and Northern Ireland
The more marketing-orientated bike companies, typified by the likes of Cervelo and Felt, will lead the market to disc brakes. And like sheep ... you will follow.


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PostPosted: Tue Feb 14, 2012 11:44 pm 
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Joined: Wed Dec 01, 2010 4:29 am
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I like the idea, especially for touring, but as always it's all about the implementation. I wonder how much of that extra 500gms will disappear when it is finally released. Another question is whether road disc brakes will be employed into a 130mm stay like the volagi :-)


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PostPosted: Tue Feb 14, 2012 11:46 pm 
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Joined: Sat Jun 07, 2008 8:50 am
Posts: 156
Location: Scotland
Another solution looking for a problem IMO. Just like electric gear shifting. I don't need them and I don't want them. But some will, and that is their choice.

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PostPosted: Tue Feb 14, 2012 11:51 pm 
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I read the article and honestly it sounds like he is looking to blame the discs for his mistakes. He does everything but admit his technique at descending was at fault. He took a bike that was meant for cyclocross out on the road, fair enough a canti equipped bike might have managed it, but you aren't going to be riding on the brakes constantly for a descent with them either.

People have used disc brakes on tandems fine

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PostPosted: Wed Feb 15, 2012 12:03 am 
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Location: Islip, NY
I think it has it's application, but not for race bikes. Why add a 160-180mm brake rotor when you have a massive rotor already at your disposal? Right now you get two functions out of the rim instead of adding more components to the mix. The article just goes to show that you can cook any brake system with poor braking technique.

I do see myself getting a disc braked bike for a sort of "all conditions" bike. Full coverage fenders, room for 28mm tires and disc brakes would be awesome for the daily grind. When I'm out in the wet, I hate hearing my rims being sanded down when I try to stop. We get a lot of sand on the roads in the winter/spring from the spreader trucks.

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PostPosted: Wed Feb 15, 2012 12:15 am 
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Valbrona wrote:
The more marketing-orientated bike companies, typified by the likes of Cervelo and Felt, will lead the market to disc brakes. And like sheep ... you will follow.


So are you still riding with down tube shifter's Valbrona or...did you follow...to STI /Ergopwer?

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PostPosted: Wed Feb 15, 2012 12:30 am 
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Joined: Sat May 09, 2009 1:52 pm
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Location: England, UK
Since when has braking power or control been a problem with modern road calipers? Usually the narrow tyre will break loose/control long before the brakes run out of power. As the article implies road bikes will use small rotors to save weight and heat build-up might be a problem for heavy brakers. Heck I've seen overheated 180mm rotors out on the MTB.

Sure disc rims won't wear out but the wheels will still be heavier since since the hubs will need rotor mounts and rotors and bizarrely I believe the rims need to be stronger to cope with the braking forces. Just look at MTB wheels. Hands up who wants heavier wheels?

The only time that I see that they are truly superior on the road is the wet, especially vs carbon rims. Having said that I guess many a serious road rider has more than one set of wheels.

Good disc brakes are great on the MTB. On Cross Bikes and Tourers etc, yes absolutely I see them.

Either way, it's another way to sell us more stuff...and as most people come I know come from MTB these days, they'll see it as good idea. So that, along with the marketing machines means we'll all get lumped with it, whether we like it or not.


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PostPosted: Wed Feb 15, 2012 12:38 am 
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Joined: Sat Oct 23, 2010 8:36 pm
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euan wrote:
I read the article and honestly it sounds like he is looking to blame the discs for his mistakes. He does everything but admit his technique at descending was at fault. He took a bike that was meant for cyclocross out on the road, fair enough a canti equipped bike might have managed it, but you aren't going to be riding on the brakes constantly for a descent with them either.

People have used disc brakes on tandems fine


Also those ultra lightweight rotors are barely good for anything.

In a recent interview with enve founder, Jason Schiers talks about how when you remove braking from a road rim, you can build the wheels out of a stronger carbon fiber, one that doesn't need to resist heat. He thinks you will see clincher rims approach current tubular rim weight. The weight argument will quickly fall away, and all you'll be left with is slightly higher spoke count.

http://www.twojohnspodcast.missingsaddl ... n-schiers/


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PostPosted: Wed Feb 15, 2012 12:54 am 
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Joined: Mon May 30, 2011 5:42 am
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euan wrote:
I read the article and honestly it sounds like he is looking to blame the discs for his mistakes. He does everything but admit his technique at descending was at fault.


This... A tyre blow out due to excessive heat can happen with poor descending technique.

I am exited about the disc revolution, especially for wet rides.


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PostPosted: Wed Feb 15, 2012 2:50 am 
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Joined: Thu Sep 02, 2010 5:54 pm
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Arguments about the pros and cons of road disks aside, while the article had some interesting bits in it I dislike how he began the article pointing out how his wreck was his own fault and ended stating the same, but the meat of the article was what was wrong with disks. Sure, he prefaced it with his mistake, but he quickly distracted you from it to make a mountain out of the engineering challenges. If I focus on the fact that I'm 40, 10 pounds too heavy, and scare everyone behind me when I wear white shorts on a ride, then why even get on a bike? Big deal! It's a few engineering obstacles that will be worked out by gen II. I'd wager dollars to Deda handlebars that any of the hurdles those guys discusses are ones their respective companies have already considered and solved.


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PostPosted: Wed Feb 15, 2012 3:22 am 
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Location: Islip, NY
Jameslee92 wrote:
Arguments about the pros and cons of road disks aside, while the article had some interesting bits in it I dislike how he began the article pointing out how his wreck was his own fault and ended stating the same, but the meat of the article was what was wrong with disks. Sure, he prefaced it with his mistake, but he quickly distracted you from it to make a mountain out of the engineering challenges. If I focus on the fact that I'm 40, 10 pounds too heavy, and scare everyone behind me when I wear white shorts on a ride, then why even get on a bike? Big deal! It's a few engineering obstacles that will be worked out by gen II. I'd wager dollars to Deda handlebars that any of the hurdles those guys discusses are ones their respective companies have already considered and solved.


Still, the big companies have to account for riders that can't ride. Telling the guy he doesn't have great technique won't hold up well in a lawsuit. They will have to design out most if not all of the user error.

Witness lawyer tabs.

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Posted: Wed Feb 15, 2012 3:22 am 


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PostPosted: Wed Feb 15, 2012 5:45 am 
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Posts: 301
It's kinda fascinating watching the reaction to that blog post. A lot of fans of disc brakes are missing the point and criticizing the guy for riding the brakes and for choosing bad equipment. He admits that right in his post though.

I think the bigger point is that people don't want to be worrying about considering equipment limitations for riding downhill on the same hills that were fine with rim brakes. So until the ones that come with popular group sets or on complete bikes are very well tested, there is a ways to go.

Personally i can't wait for a good road disc brake. My xc bike's Maguras are to die for.


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