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Disc Brakes on Touring Bikes



 
 
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  #11  
Old July 22nd 03, 06:51 PM
Rick Warner
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Default Disc Brakes on Touring Bikes

(Pheonix Ribbon) wrote in message . com...
I am in the process of building a touring bike that will last me the
ages. I have found my frame (
www.vanguard.com). It has housings for
both disc and v-brakes. Now, I know that it is best to stick to simple
brakes when out in the middle of nowhere, and I shall be using
v-brakes when I'm touring down Europe. But would still like to knwo if
it is possible to find/build-easily a drop handle lever that will be
able to operate a set of disc brakes.

Any ideas?

As we are on subject, if anyone can recommend a good set of
fully-loaded touring forks, then please divulge.

Many thanks,

Lief


Everybody seems to be concentrating on the mechanics of the brakes,
levers, etc., but no one has mentioned one issue with discs and touring
bikes: interference with racks! Not an impossible combination, but the
standard mount will interfere with racks. Things gotta be moved to make
it all work.

- rick
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  #12  
Old July 22nd 03, 11:27 PM
Todd Kuzma
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Default Disc Brakes on Touring Bikes

There are a few concerns with disk brakes on touring bikes.
First, to accomodate the rotor, the hub flange spacing
must be narrower. This will result in a wheel which is not
as strong. Additionally, the front wheel will have dish.

Second, the frame and fork need to be beefy to handle the
torque from the brake. On the rear this just means extra
weight. However, on the front, it also means a very stiff
fork which will adversely affect ride quality.

Third, it is difficult, but not impossible, to fit racks
around many disk calipers.

Fourth, there is evidence to suggest that a front disk brake
can force a wheel from the dropouts unless there is some
sort of secondary retention device (like lawyer lips) or
other provision to prevent this.

Fifth, there has also been some evidence that rim brakes can
generate more sustained braking power and dissipate more
heat prior to failure than most disk brakes. Rim brakes
fail from excessive heat by blowing a tire off of the rim.
Disk brakes fail frome excessive heat in a variety of ways:
boiling fluid, warped rotors, melted plastic parts, glazed
pads, etc. Generally speaking, rim brakes will tolerate a
higher level of heat than most disk brakes. The best disk
brakes in this regard are those with heavy, large diameter
rotors. These can be superior to rim brakes in heat
dissipation.

The main advantage of disks in mountain biking is
performance in muddy conditions when rim brakes would be
packed with mud. This generally isn't an issue for touring
bikes (unless off-road touring). Both rim and disk brakes
need to clear the braking surface of water before effective
braking can begin so there is no clear advantage for either
in the rain.

Todd Kuzma
Heron Bicycles
Tullio's Big Dog Cyclery
LaSalle, Il 815-223-1776
http://www.heronbicycles.com
http://www.tullios.com

  #13  
Old July 22nd 03, 11:42 PM
Jose Rizal
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Default Disc Brakes on Touring Bikes

Todd Kuzma:

Fifth, there has also been some evidence that rim brakes can
generate more sustained braking power and dissipate more
heat prior to failure than most disk brakes. Rim brakes
fail from excessive heat by blowing a tire off of the rim.
Disk brakes fail frome excessive heat in a variety of ways:
boiling fluid, warped rotors, melted plastic parts, glazed
pads, etc. Generally speaking, rim brakes will tolerate a
higher level of heat than most disk brakes.


Blowing a tire off a rim is a catastrophic failure with rim brakes, not
good when going down an incline, whereas a warped disk rotor will not
have as dramatic an effect. A disk brake system is better in this
respect.


  #14  
Old July 23rd 03, 12:45 AM
(Pete Cresswell)
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Default Disc Brakes on Touring Bikes

RE/
And BTW non-original pads won't fit. There is an auxiliary spacer spring
that fits around the pad material tightly. Avid shapes their material to
allow it to fit. Non-originals were caught by 2001 model magnetic mounting
example and have not "fitted" their material exactly, resulting in the
spacer spring not fitting, in my experience.


Also, if you're using the Avids, take a couple of spare springs along with those
spare sets of pads.

I had one set of pads just fall out of the calipers on me - leaving behind a
mangled spring. To be fair to Avid, I suspect I brought it on by incorrectly
inserting the rear wheel once (the rotor probably caught the little tab that
protrudes from the spring clip)...but it *did* happen.....

Also, make sure you trim the cable ends close. One guy posted either here or in
the MTB group that a friend did an endo at speed as the tail of the brake wire
somehow got caught in the caliper body.
-----------------------
PeteCresswell
  #15  
Old July 23rd 03, 01:43 AM
Chalo
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Default Disc Brakes on Touring Bikes

"Michael Dart" wrote:

Avid Mechanical ball bearing disc brakes are then next best thing to
hydraulic discs and better than V's.


Speaking as a 360 lb. rider who can use braking power and not just
braking feel, and who's tried most every kind of brake, the order of
those three brakes is reversed from a max. power standpoint.
Cantilevers and Vs can stop harder, longer. And Avid mechanical
brakes have the benefit of being tunable (through choice and/or
adjustment of the lever) with regard to mechanical advantage.

Hydraulic discs offer no leverage adjustment, and they become
overheated just as easily as mechanical discs in an equivalent rotor
size. People who don't actually use all their available braking power
become impressed with the lever response of hydraulic discs and assume
that their greater sensitivity to lever pressure means that they are
more powerful than other brakes. They are not.

They make a version for road bikes.
They are quite simple and probably easier to set up and maintain than V's or
Canti's.


Easier to set up well than cantis, maybe. Easier than V-brakes? No
way. If you have to seal your own hoses and bleed the system (such as
when installing almost any unusual setup), any mechanical brake has
simpler setup.

One point the OP should note is that disc brakes make for a dished,
weak front wheel. They reduce the amount of dish in the rear wheel,
though, which is good. If the rear rack mounting issues can be worked
out with a rear disc in place, then this might be an OK place to use a
disc on a touring bike. You're better off with a canti brake, and a
dishless wheel, in the front.

Chalo Colina
  #16  
Old July 23rd 03, 01:44 AM
Chalo
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Default Disc Brakes on Touring Bikes

"Michael Dart" wrote:

Avid Mechanical ball bearing disc brakes are then next best thing to
hydraulic discs and better than V's.


Speaking as a 360 lb. rider who can use braking power and not just
braking feel, and who's tried most every kind of brake, the order of
those three brakes is reversed from a max. power standpoint.
Cantilevers and Vs can stop harder, longer. And Avid mechanical
brakes have the benefit of being tunable (through choice and/or
adjustment of the lever) with regard to mechanical advantage.

Hydraulic discs offer no leverage adjustment, and they become
overheated just as easily as mechanical discs in an equivalent rotor
size. People who don't actually use all their available braking power
become impressed with the lever response of hydraulic discs and assume
that their greater sensitivity to lever pressure means that they are
more powerful than other brakes. They are not.

They make a version for road bikes.
They are quite simple and probably easier to set up and maintain than V's or
Canti's.


Easier to set up well than cantis, maybe. Easier than V-brakes? No
way. If you have to seal your own hoses and bleed the system (such as
when installing almost any unusual setup), any mechanical brake has
simpler setup.

One point the OP should note is that disc brakes make for a dished,
weak front wheel. They reduce the amount of dish in the rear wheel,
though, which is good. If the rear rack mounting issues can be worked
out with a rear disc in place, then this might be an OK place to use a
disc on a touring bike. You're better off with a canti brake, and a
dishless wheel, in the front.

Chalo Colina
  #17  
Old July 23rd 03, 02:04 AM
Todd Kuzma
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Default Disc Brakes on Touring Bikes

Jose Rizal wrote:

Blowing a tire off a rim is a catastrophic failure with rim brakes, not
good when going down an incline, whereas a warped disk rotor will not
have as dramatic an effect. A disk brake system is better in this
respect.


That's true although losing your brakes ain't no picnic.
This reminds me of another issue. If you damage a rotor in
an accident, you will have to remove it to continue. Not a
big problem, but it has happened to mountain bikers.

Todd Kuzma

  #18  
Old July 23rd 03, 02:59 AM
James Annan
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Default Disc Brakes on Touring Bikes

Todd Kuzma wrote in message ...

Fourth, there is evidence to suggest that a front disk brake
can force a wheel from the dropouts unless there is some
sort of secondary retention device (like lawyer lips) or
other provision to prevent this.


Four and a halfth, there is evidence to suggest that even if retention
lips are present, the skewer can still be loosened sufficiently for
wheel loss to result.

James
  #20  
Old July 23rd 03, 10:01 PM
Chalo
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Default Disc Brakes on Touring Bikes

Todd Kuzma wrote:

First, to accomodate the rotor, the hub flange spacing
must be narrower. This will result in a wheel which is not
as strong.


Actually, the resulting rear wheel may be less stiff laterally, but
can almost certainly be built stronger (more load capacity) with less
dish. Many tandem rear hubs have been built symmetrical or nearly
symmetrical for this reason, though it means that flange spacing will
be narrow.

I am not convinced that disc brakes have any advantages on a touring
bike, but in the rear at least, they will not compromise wheel
strength.

Chalo Colina
 




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