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Why don't road bikes have front disc brakes?

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Road Cycling “It is by riding a bicycle that you learn the contours of a country best, since you have to sweat up the hills and coast down them. Thus you remember them as they actually are, while in a motor car only a high hill impresses you, and you have no such accurate remembrance of country you have driven through as you gain by riding a bicycle.” -- Ernest Hemingway

Why don't road bikes have front disc brakes?

Old 04-20-07, 11:51 PM
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Why don't road bikes have front disc brakes?

I was just riding my neighbor's high-end mountain bike since it is raining here in socal and I didn't want to get my road bike dirty. I noticed it was one of those types with disc brakes. I started playing around to get a feel for their power and I was able to do stoppies (lifting the rear wheel off the ground) with firm front brake pressure. The power was phenominal. I felt like I could stop on a dime at low speeds.

Why don''t road bikes come with disc brakes or at least have them available for aftermarket add-ons? Keep in mind that I had Dura Ace brakes on my last road bike, so it's not like I've only experienced low end brakes. It would be sweet to have that kind of stopping power on a road bike capable of 40mph sprints.
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Old 04-20-07, 11:53 PM
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weight?
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Old 04-20-07, 11:55 PM
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Carbon forks are too weak to support the brakes without breaking. Disc brakes on MTBs are mounted on very stout magnesium lowers with lots of strength. Disc brakes put huge amounts of force into the fork. If you want disc brakes on a roadie, the fork would have to be VERY heavy to have the necessary strength.

The disc brakes themselves are also heavier than dual pivot brakes.
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Old 04-21-07, 12:19 AM
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1) weight
2) resistance to change
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Old 04-21-07, 12:55 AM
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As you said you could lift the rear wheel off the ground. Big companies understand the words "endo" and "liability". Front discs do make sense on a tandem. See the 10 inch rotors on some Santana tandems.
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Old 04-21-07, 12:58 AM
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Give it a couple of years...Campagnolo and Shimano will find ways to make disc brakes compatible with contemporary forks so roadriders can take advantage of the massive stopping power of those brakes.
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Old 04-21-07, 01:02 AM
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I don't really mind the rim brakes on my roadie. I think it is about maintenance and up-keep. My v-brakes on my mountain bike stop better than my roommate's mechanical discs by far and his are relatively new.
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Old 04-21-07, 01:08 AM
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A mtn bike has a much larger contact area between the tire and the ground---your road bike has very little. It takes very little to lock up a wheel on a road bike as it is. It makes no sense to have that more braking power when it really cannot be used. Secondly, how much technical braking do you require on a road bike, unless you are on some crazy technical descent?
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Old 04-21-07, 01:26 AM
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Some cyclocross bikes have discs, though I'm not sure whether they had carbon forks. I think they did?
I remember my old hybrid, which had such nice brakes. The stopping power gives you so much confidence. On the road bike the brakes work well enough, but once they heat up...

Weight doesn't bother me too much, and I would definately put a hydraulic disc on the front if I had the option to. The only worrying thing would be locking the wheel, but good brakes have excellent modulation.
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Old 04-21-07, 01:37 AM
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Trek Portland, Kona Sutra, Schwinn DBX... these are sort-of "road" bikes with discs (and carbon forks).

The big advantage of discs is consistent and clean braking in all weather conditions. They are great for commuting, but the added weight make them disadvantageous for racing.
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Old 04-21-07, 01:49 AM
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If you like a road bike , yet don't race, why not? Doing moutain touring, I think disc brakes are catching on for certain touring/hybrid type bikes. I like the tought of consistent braking when doing mountain work.
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Old 04-21-07, 03:36 AM
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Originally Posted by filtersweep
A mtn bike has a much larger contact area between the tire and the ground---your road bike has very little. It takes very little to lock up a wheel on a road bike as it is. It makes no sense to have that more braking power when it really cannot be used.
Agreed. I think that's the best reason - good v-brakes are powerful enough to bring road tires to the limit of friction anyway (in most conditions) so there's no advantage in using disc brakes.

Yes MTBs do stop better but you won't manage that same deceleration on a roadbike without using wide MTB tires too. The reason that some hybrids and tourers are starting to use disc brakes is for their better performance in very wet conditions, and consistency over long periods, but these aren't worth the tradeoff in weight and parts on a roadbike.

Last edited by Endox; 04-21-07 at 03:49 AM.
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Old 04-21-07, 06:06 AM
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The nice thing with discs on a moutain bike is they work wet and dirty. I don't see much advantage on the road unless you ride your bike when it is wet and dirty.
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Old 04-21-07, 06:37 AM
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Originally Posted by Mach42
Carbon forks are too weak to support the brakes without breaking. Disc brakes on MTBs are mounted on very stout magnesium lowers with lots of strength. Disc brakes put huge amounts of force into the fork. If you want disc brakes on a roadie, the fork would have to be VERY heavy to have the necessary strength.
Someone better tell that to Co-Motion. Their tandems are available with an all-carbon fork and disc brakes...
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Old 04-21-07, 06:53 AM
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Here's a road bike (touring bike) with disc brakes.

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Old 04-21-07, 07:07 AM
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Originally Posted by 2manybikes
Here's a road bike (touring bike) with disc brakes.

Yeah, mine was black and it weighed 34 lbs for commuting!
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Old 04-21-07, 07:11 AM
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Originally Posted by slvoid
Yeah, mine was black and it weighed 34 lbs for commuting!
Hehe... this one's around 27. The Rolf carbon tubulars are particularly schweet...

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Old 04-21-07, 07:12 AM
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Originally Posted by DrPete
Someone better tell that to Co-Motion. Their tandems are available with an all-carbon fork and disc brakes...
I guess it's a lot harder to do an endo on a tandem, and there's a lot more weight to be braked, so the disks are more appropriate there than on a single person road bike.
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Old 04-21-07, 07:13 AM
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Originally Posted by cooker
I guess it's a lot harder to do an endo on a tandem, and there's a lot more weight to be braked, so the disks are more appropriate there than on a single person road bike.
Very true--I was just pointing out the "no disc brakes with a carbon fork" fallacy.
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Old 04-21-07, 07:17 AM
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Originally Posted by slvoid
Yeah, mine was black and it weighed 34 lbs for commuting!
It sounds like you enjoyed it, and it was a great bike for that application. wow 34 lbs.
Well my 1970's Schwinn continental weighs 40 lbs.
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Old 04-21-07, 07:20 AM
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Originally Posted by DrPete
Hehe... this one's around 27. The Rolf carbon tubulars are particularly schweet...

Holy !@#$%^!

It must be hard to find a stoker that weighs 57 lbs.
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Old 04-21-07, 07:31 AM
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Originally Posted by DrPete
Someone better tell that to Co-Motion. Their tandems are available with an all-carbon fork and disc brakes...
You usually don't go over the bars with a tandem- to load the carbon fork. With decent brakes, the back end usually finds a way to come around like a semi, to the surprise of your partner!
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Old 04-21-07, 07:33 AM
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Originally Posted by rufvelo
You usually don't go over the bars with a tandem- to load the carbon fork. With decent brakes, the back end usually finds a way to come around like a semi, to the surprise of your partner!
Yeah, I did that once... ONCE. Fortunately we still got married. From that day forward I decided not to approach stop signs at the bottom of hills sideways.
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Old 04-21-07, 07:43 AM
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A couple years back Red Bull had an event called the "Road Rage", where invited riders raced a steep downhill road, Tuna Canyon. Top speeds were near 60mph and there were sharp turns. Avid was partial sponser and riders were encouraged to use disc brakes, and some did, but the event was won by Myles Rockwell on a standard road bike. Avid had a special brake, but I don't know if it ever made it into production. It would be good to have consistant, all-weather stopping power in the mountains, especially for Clydes like me.
BTW, is this endo thing really a concern? Have you ever done or even seen an endo on a road bike from too much brake? Was the endo-er a total dweeb?
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Old 04-21-07, 07:50 AM
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Originally Posted by DrPete
Someone better tell that to Co-Motion. Their tandems are available with an all-carbon fork and disc brakes...
Yep...



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