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School me on disk brakes on a road bike....

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School me on disk brakes on a road bike....

Old 10-08-10, 10:16 AM
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accordionfolder
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School me on disk brakes on a road bike....

I have a nefarious plot that has slowly developed in my mind to swap my front fork on my Trek 1000 (an aging carbon fiber piece...) to a disk compliant one (kona ... something like that). Now my questions is, can I get levers that play nice with typical cartridge road brake in the back and a disk up front?

https://cgi.ebay.com/NEW-TEKTRO-R200-...#ht_2623wt_905

These lever preferably....

Thanks!
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Old 10-08-10, 10:21 AM
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If you go with Avid BB7's in the road version they'll play just fine even with STI levers.
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Old 10-08-10, 11:00 AM
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I have a cyclocross bike ( Novara Element ) with drop handlebars, skinny tires, and disc brakes. It's got Tiagra brifters, and I'm pretty sure there are Avid BB7s on the thing. ( It's downstairs, out of checking range. )

There are no words for how much I prefer disc brakes in the rain.
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Old 10-08-10, 11:19 AM
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You can 1. Replace the brake lever for the disc brake with a long pull specific lever (this works well, but the pivot geometry on the levers is a bit different, and I personally think they're harder to use from the hoods as a result)

2. Use a cable travel adjuster. These work, but they're extra complexity, weight, and one more thing that can get gummed up, and some models are bad for that.

3. Use a short pull (road) specific disc brake. The Avid BB7 Road is the only one I'm aware of, but it is really one of the best (if not the best) mechanical disc brake to begin with.

I personally recommend #3, the bb7 road disc brake is the most polished and simple solution to begin with, and if you are buying a disc brake anyways, it saves you from needing other junk.
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Old 10-08-10, 11:40 AM
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Isn't there a road version of the BB5s? How much worse are they?
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Old 10-08-10, 12:03 PM
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Originally Posted by tjspiel View Post
Isn't there a road version of the BB5s? How much worse are they?
My general impression is that the BB5s just don't adjust up as nicely as the BB7s. I always had either a very little bit of drag, or too much "throw" when actuating the brakes (if I adjusted out the drag). Beyond that, the BB5s worked great, at least in my case.
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Old 10-08-10, 12:15 PM
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Get the BB7 road and don't worry about the levers. I've been delighted with mine.

You're probably aware of this, but it's not just a fork swap. You'll have to get a new wheel with a disc hub, or rebuild the one you have.
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Old 10-08-10, 12:58 PM
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Yeah, I'm aware of the hub swap (my front hub is pretty shot anyways ..), thanks for all the info! I thought there was a road going version disk caliper, I just didn't know what it was called

Thanks!
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Old 10-08-10, 01:03 PM
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Oh, and some set up for my wanting to do this: I T-boned a car because of sub par braking capabilities

Fortunately I was alright, and it was his fault, but I would have rather not hit him at all.

Now here is another question:

I worry about a panic brake induced endo. Is this a major problem with such a short, light bike? In many circumstances it would be much worse for me to panic and endo under a car then it would be for me to just bounce (painfully) off of the side of it.
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Old 10-08-10, 02:14 PM
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I am going to jump in here with a rant on why I don't think that disc brakes make sense on a road bike.

first is the physics of the design - to stop the bike, your tires need to exert a negative force on the pavement. In the case of a traditional brake, the mechanism that does this is to apply pressure directly to the rim of the wheel, which translates the pressure to the tire and then to the pavement - all pretty straightforward.

With a disk brake, the calipers apply pressure to the disk, which in turn applies pressure to the hub, which applies the lateral pressure to the rim and then the tire through the spokes. The spokes (especially on a front wheel) are primarily designed to apply radial, not lateral pressure, so in order to accommodate the braking forces, you will want to use a lacing pattern which takes this into account. The net result will be more, longer, and beefier spokes on the front wheel than you would otherwise need.

The next issue is again one of physics - the pressure that needs to be exerted by a traditional brake pad on the rim of the wheel is approximately equal to the pressure that the tire is exerting on the pavement. For a disk brake, the disk is much smaller than the diameter of the wheel, so the amount of pressure that needs to be exerted is multiplied by the ratio of the disk diameter to the rim diameter - which can easily be 8:1 or more. This large force is applied to the fork near the dropouts, so the design of the fork needs to accommodate this as well, meaning that to support the disc brake you will need a heavier, stronger front fork.

The next issue is one of thermal dissipation - when you are slowing your bike, you are doing so by converting the kinetic energy of the bicycle to thermal energy, mostly in the brake pads and the braking surface. In the case of a traditional brake, this heat is generated in the rim of the wheel, and there is a lot of area over which it can be distributed, and dissipated. With a disk brake, all this thermal energy is transferred into a relatively small disk.

There are some advantages to disk brakes primarily when riding in wet conditions where the distance between the braking surface and the road helps to keep the brakes drier, but I believe that this is more of an advantage in mountain bikes than on road bikes.
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Old 10-08-10, 02:38 PM
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Well you've taken into account all of the purely mathematical reasons why one should avoid disks, but you haven't taken into account a whole slew of other reasons. Such as ease in tuning, ease in brake pad exchange, no rim wear (easier/cheaper to replace a disk than a rim), and how cool it looks .

In all seriousness though, I want this on my commuter where I frequently have to go through stop and go traffic, which is horrific on my standard cartridge brakes. The few disk brakes I have used have ALWAYS felt more powerful than the best of my rim brakes. Braking power is important when a car makes a sudden stop/turns in front of you.

So until I find out some terrifying reason that I shouldn't run them, it is still my plan. Thanks for the input!
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Old 10-08-10, 03:05 PM
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Originally Posted by sauerwald View Post
I am going to jump in here with a rant on why I don't think that disc brakes make sense on a road bike.

first is the physics of the design - to stop the bike, your tires need to exert a negative force on the pavement. In the case of a traditional brake, the mechanism that does this is to apply pressure directly to the rim of the wheel, which translates the pressure to the tire and then to the pavement - all pretty straightforward.

With a disk brake, the calipers apply pressure to the disk, which in turn applies pressure to the hub, which applies the lateral pressure to the rim and then the tire through the spokes. The spokes (especially on a front wheel) are primarily designed to apply radial, not lateral pressure, so in order to accommodate the braking forces, you will want to use a lacing pattern which takes this into account. The net result will be more, longer, and beefier spokes on the front wheel than you would otherwise need.

The next issue is again one of physics - the pressure that needs to be exerted by a traditional brake pad on the rim of the wheel is approximately equal to the pressure that the tire is exerting on the pavement. For a disk brake, the disk is much smaller than the diameter of the wheel, so the amount of pressure that needs to be exerted is multiplied by the ratio of the disk diameter to the rim diameter - which can easily be 8:1 or more. This large force is applied to the fork near the dropouts, so the design of the fork needs to accommodate this as well, meaning that to support the disc brake you will need a heavier, stronger front fork.

The next issue is one of thermal dissipation - when you are slowing your bike, you are doing so by converting the kinetic energy of the bicycle to thermal energy, mostly in the brake pads and the braking surface. In the case of a traditional brake, this heat is generated in the rim of the wheel, and there is a lot of area over which it can be distributed, and dissipated. With a disk brake, all this thermal energy is transferred into a relatively small disk.

There are some advantages to disk brakes primarily when riding in wet conditions where the distance between the braking surface and the road helps to keep the brakes drier, but I believe that this is more of an advantage in mountain bikes than on road bikes.
I don't think you'll ever see disk brakes commonly employed on road racing bikes, but they do have their place on commuting bikes. An extra pound or two added by brake disks and beefing up the rest of the bike isn't really that big of a deal unless you're commuting up a mountain. I'm not so sure that thermal dissipation is a big problem, either--the disk might get hot, but unlike the rim, it's not anywhere close to critical parts (tubes, tires) that can go boom if they overheat. Just don't touch your brake disks right after you get to the bottom of a big downhill.

As for the advantages, I'd say that by and large disks won't stop you any quicker than rim brakes--even in the wet, it's pretty easy to reach the limits of tire/road adhesion with a well-adjusted set of rim brakes. However, I would argue that the principal advantage of disks is wheel longevity and ease of maintenance, particularly in wet weather. Road grit tends to wear down rim surfaces in a hurry if you do a lot of braking in wet weather and/or snow. I find even my BB5s (pretty much the bottom end as far as road-oriented disks are concerned) are less fiddly to maintain than the V-brakes and cantilevers I've had on other foul-weather commuting bikes in the past.

So yeah, maybe they're not so necessary in San Jose, but I can sure see why people up in the Pacific Northwest swear by their disks.
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Old 10-08-10, 03:31 PM
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I replaced my front fork with a disc fork and upgraded to a disc/generator hub at the same time. I love the decreased braking time. Lots of road disc frame coming out, esp since the UCI legalised discs for cyclocross. Salsa has the Vaya in steel and Ti, Steelwool Tweed, Civia Bryant and Soma Double Cross DC just to name a few.
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Old 10-09-10, 08:29 AM
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Originally Posted by accordionfolder View Post
Now here is another question:

I worry about a panic brake induced endo. Is this a major problem with such a short, light bike? In many circumstances it would be much worse for me to panic and endo under a car then it would be for me to just bounce (painfully) off of the side of it.
Put your weight back when you brake and you won't endo. At least not on pavement, anyway -- use more rear brake when you're going downhill in dirt or grass and be very aware of the front brake.
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Old 10-09-10, 09:03 AM
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Originally Posted by Mr IGH View Post
the UCI legalised discs for cyclocross.
This has me stalling on any upgrades to see how long it takes to produce a hydraulic STI lever set for drop bars.
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Old 10-09-10, 10:36 AM
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German Bike industry trade show showed a prototype cable operated double master cylinder, that fit under the stem.

to do that very thing,. adapt .. won't expect to see and Brifter and hydraulic master cylinder,
any time soon, if ever,
because there is not enough internal room in normal 3 dimensional space for both..
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Old 10-09-10, 10:40 AM
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Originally Posted by tjspiel View Post
Isn't there a road version of the BB5s? How much worse are they?
Both the BB5 and BB7 are available is a road version and a mtn version.
Be very careful when ordering them to ensure you are getting the correct version.
I have seen a number of online sites selling them, but not specifying which version they are shipping.
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Old 10-09-10, 11:19 AM
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Originally Posted by fietsbob View Post
German Bike industry trade show showed a prototype cable operated double master cylinder, that fit under the stem.

to do that very thing,. adapt .. won't expect to see and Brifter and hydraulic master cylinder,
any time soon, if ever,
because there is not enough internal room in normal 3 dimensional space for both..
Found some links:
https://www.bikeradar.com/news/articl...onverter-27723
https://www.bikeradar.com/gallery/art...rticle%2Fimage
https://www.velocipedesalon.com/forum...gun-17402.html
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Old 10-09-10, 12:25 PM
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Some more stuff on hydros

You might have to click on 'Translating' to see the following 3 links as they are a translated version.

Hope Conversion

Magura Conversion

DBikes Conversion

Original Pages:
https://www.felix.ch/shop/01_shop/detail_felix.php?code=FE-058.501
https://velotraum.de/news/konverter-fuer-rennrad-sti-schalthebel-und-hydraulische-scheibenbremse
https://www.dbikes.ch/dbikes_konverter.html

Sticha has 2 dropbar road bikes with hydros, the Morati SC 1.2 Discjockey and the Morati SR 1.1
Velotraum seems to custom fit the hydros to various bike models.



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Old 10-09-10, 09:00 PM
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I did not know these products existed.

The Hope one looks pretty slick, but $700 CAD is almost six times what I paid for the hydraulic STI levers (flat-bar) on my mountain bike (ST-M775).

I'll keep waiting.
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Old 10-09-10, 11:05 PM
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$700 good lord.

Disc brake make lotta sense on the road, i have some on my commuter and in the rain ride two of us have to emergency stop... buddy on his rig had no disc brake and he ends up at least a meter ahead, in fact he almost hit my rear wheel because of water on this rim.

Disc brake are particularly valuable for saving you that extra little wheel length between going over a hood or into a door.

get the bb7, the inner pad can be adjusted as well as the outer pad - it makes for a more accurate system.
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Old 10-10-10, 03:00 PM
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Originally Posted by jefferee View Post
As for the advantages, I'd say that by and large disks won't stop you any quicker than rim brakes--even in the wet, it's pretty easy to reach the limits of tire/road adhesion with a well-adjusted set of rim brakes.
I'll disagree with this. Rim brakes there's always at least that single rotation where the brakes are stripping the water from the rim. Discs have more of a tendency to be there as soon as they're applied. Secondly, since discs are further from the tire they're somewhat more isolated from crap/debris/water/oil than a rim sidewall is and subsequently less likely to be affected.
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Old 10-10-10, 03:36 PM
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Originally Posted by fietsbob View Post
German Bike industry trade show showed a prototype cable operated double master cylinder, that fit under the stem.

to do that very thing,. adapt .. won't expect to see and Brifter and hydraulic master cylinder,
any time soon, if ever,
because there is not enough internal room in normal 3 dimensional space for both
..
Try thinking outside the box...or inside the handlebar
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Old 10-10-10, 03:46 PM
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Putting a hydraulic topmount lever with the cable to hydraulic actuator built into the lever body, is smart..
the Swiss have Clever Engineers .
That guy they hired in the patent office that dreamed up the theory of relativity , went on to do big things.
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Old 10-14-10, 07:31 PM
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Also there are cyclocross bikes with disc brakes. Great commuter choice. I may sell three of my bikes and replace them with a cross disc
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