Disc Brakes for loaded touring

Robert Strickland said:

I followed a thread about disc brakes a while back in which some folks said that they thought disc
brakes didn't make sense on a road bike. The arguments made sense to me. It seems likely that
you'd trade extra hassle, weight and money for no real substantial benefits. What I'm wondering is
if you all think they make sense for loaded touring. I'm planning to have my steel touring-frame
stripped and re-painted and I then plan to build up a (mostly Campy) loaded touring bike. I was
thinking that disc brakes might make sense and since I'm having the frame repainted I might think
about adding disc brake mounts. Any thoughts on this? I should make clear that I don't have any
real knowledge about disc brakes. What would be the pro's and con's besides better wet or muddy
braking and stronger brakes for heavy loads?

You can't put a disc-brake on a conventional fork safely for two reasons, the fork end cannot
withstand the bending moment introduced at it's flimsy narrow end, and if you did use one, the front
wheel would disengage when braking unless you got dropouts with lawyer lips. Hub brakes introduce
bending moments at the dropout similar to those at the fork crown. That is why fork blades are large
and oval at the crown.

You might just go back and read the thread on wheel disengagement of disc-brake bicycles. This stuff
has not been well thought out. Disk brake bicycles should have conical sunk dropouts so that the up
and down forces from road and brake do not cause motion.

Jobst Brandt [email hidden] Palo Alto CA

Robert Strickland said:

I followed a thread about disc brakes a while back in which some folks said that they thought disc
brakes didn't make sense on a road bike. The arguments made sense to me. It seems likely that
you'd trade extra hassle, weight and money for no real substantial benefits. What I'm wondering is
if you all think they make sense for loaded touring.

...

Quoted message said:

What would be the pro's and con's besides better wet or muddy braking and stronger brakes for
heavy loads? Thanks in advance.

Most disc brakes can't sustain a comparable level of braking power (as continuous watts dissipated)
to a rim brake with a sturdy touring tire and tube. The way in which they could be called "stronger"
than a rim brake in a given application is in their ratio of braking torque to lever effort. That
is, you won't be able to brake any harder or longer with discs before they fail; you just won't have
to squeeze as hard to get them to that point.

In addition to the improved wet/muddy braking you mentioned, there are other possible benefits:

No rim wear from braking Reduced brake [censored] from wet riding May interfere less with luggage racks
May allow use of fenders with fatter tires Can allow use of different rim diameters Out-of-true
wheel less likely to rub

and possible disadvantages:

Dished front wheel-- much weaker Rotors seem to warp more easily than rims More vulnerable to damage
in a tipover Hydraulics fail totally when they fail Dedicated levers for hydraulics Fixed ratio for
mechanical discs; less tunable than cantis Possibility of QR wheel ejection/lockup (!!)

For reliability, configurability and proven performance, cantilever brakes still seem like the way
to go. Unless you crave the ability to swap between 26" and 700c wheels, and have the tire clearance
to exploit this option, it's hard to make a case for discs on a touring bike.

If you can't get equal or better braking from cantilever brakes under normal conditions, you're just
not setting them up to deliver their best.

That said, disc brakes have improved enough recently that if you want to use them anyway, they
probably won't disappoint you. Magura and Hayes hydraulics and Avid cable-actuated brakes are all
pretty safe bets, and bigger rotors appear to be better, all else equal.

Chalo Colina

Robert-<< What I'm wondering is if you all think they make sense for loaded touring.

I do, loaded touring, tandems, cross bikes, some MTB bikes, hydraulic discs make great sense.

<< I'm planning to have my steel touring-frame stripped and re-painted and I then plan to build up a
(mostly Campy) loaded touring bike. I was thinking that disc brakes might make sense and since I'm
having the frame repainted I might think about adding disc brake mounts.

I think mechanical discs are not much of an improvement over really good cantis tho-all you will be
able to use with ERGO..

<< What would be the pro's and con's besides better wet or muddy braking and stronger brakes for
heavy loads?

May not be number two in the case of mechanicals...

Peter Chisholm Vecchio's Bicicletteria 1833 Pearl St. Boulder, CO, 80302
(303)440-3535 vecchios.comvecchios.comOpen ↗ "Ruote convenzionali costruite eccezionalmente bene"

Bluto said:

For reliability, configurability and proven performance, cantilever brakes still seem like the
way to go.

There's still a few Suntour self-energising rears out there, too.
--
David Damerell <[email hidden]> flcl?

"Bluto" <[email hidden]> wrote in message
"]news:[email hidden]...

Quoted message said:

Robert Strickland said:

I followed a thread about disc brakes a while back in

which some folks said

Quoted message said:

Quoted message said:

that they thought disc brakes didn't make sense on a

road bike. The

Quoted message said:

Quoted message said:

arguments made sense to me. It seems likely that you'd

trade extra hassle,

Quoted message said:

Quoted message said:

weight and money for no real substantial benefits. What

I'm wondering is if

Quoted message said:

Quoted message said:

you all think they make sense for loaded touring.

...

Quoted message said:

What would be the pro's and con's besides better wet or muddy braking and stronger

brakes for heavy

Quoted message said:

Quoted message said:

loads? Thanks in advance.

Most disc brakes can't sustain a comparable level of

braking power (as

Quoted message said:

continuous watts dissipated) to a rim brake with a sturdy

touring tire

Quoted message said:

and tube. The way in which they could be called

"stronger" than a rim

Quoted message said:

brake in a given application is in their ratio of braking

torque to

Quoted message said:

lever effort. That is, you won't be able to brake any

harder or

Quoted message said:

longer with discs before they fail; you just won't have to

squeeze as

Quoted message said:

hard to get them to that point.

This is the heart of the issue. Braking converts kinetic energy to heat, which is dissipated into
the air. Your wheel rims are larger, and have more mass, than any normal disk brake on the market.
This means they can dissipate heat better, plus they can absorb more heat without becoming
incredibly hot.

In fact most disc brakes sold for MTB use become inadequate on long, high speed descents. And that's
on trails where really high speeds are hardly reached, and not for long, plus the load is just a
rider -- no heavy touring bags, etc. A fully loaded touring bike on a long, highway descent would
overheat these brakes very quickly. Special, larger disc brakes are sold for downhill racing bikes
and tandems --and they're necessary.

The advantages of disc brakes are consistency, modulation, and precision, especially where mud
and dirt can foul the rims. They give more control, and better threshold braking ability.
However, rim brakes ultimately have more power, that being defined as the ability to dissipate
heat on a long descent.

If you really want disc brakes for your touring bike, you'd need larger than normal ones, like
tandem or downhill racing models. These are specialized equipment and therefore expensive, plus
they'd probably need specially made forks and frames -- expensive too.

A drag brake, such as those used by tandem riders, is probably a better solution. However, most
loaded tourers seem to do without these just fine.

One thing you might look into are Magura hydraulic rim brakes, which are exremely powerful and
reliable. If I had a tandem, I'd probably choose these. This would preclude STI/Ergo, though.

Quoted message said:

In addition to the improved wet/muddy braking you

mentioned, there are

Quoted message said:

other possible benefits:

No rim wear from braking Reduced brake [censored] from wet riding May interfere less with luggage racks
May allow use of fenders with fatter tires Can allow use of different rim diameters Out-of-true
wheel less likely to rub

and possible disadvantages:

Dished front wheel-- much weaker Rotors seem to warp more easily than rims More vulnerable to
damage in a tipover Hydraulics fail totally when they fail Dedicated levers for hydraulics Fixed
ratio for mechanical discs; less tunable than cantis Possibility of QR wheel ejection/lockup (!!)

For reliability, configurability and proven performance,

cantilever

Quoted message said:

brakes still seem like the way to go. Unless you crave

the ability to

Quoted message said:

swap between 26" and 700c wheels, and have the tire

clearance to

Quoted message said:

exploit this option, it's hard to make a case for discs on

a touring

Quoted message said:

bike.

If you can't get equal or better braking from cantilever

brakes under

Quoted message said:

normal conditions, you're just not setting them up to

deliver their

Quoted message said:

best.

That said, disc brakes have improved enough recently that

if you want

Quoted message said:

to use them anyway, they probably won't disappoint you.

Magura and

Quoted message said:

Hayes hydraulics and Avid cable-actuated brakes are all

pretty safe

Quoted message said:

bets,

All good points.

Quoted message said:

and bigger rotors appear to be better, all else equal.

The bottom line is that while newer models work very well indeed, there's no getting around the
smaller size/mass of the rotor, compared to a rim.

Matt O.

Quoted message said:

Disk brake bicycles should have conical sunk dropouts so that the up and down forces from road and
brake do not cause motion.

Can you give more detail? I'm having a custom fork made for a disc-brake road bike, so I'd like to
build in whatever safety features I can.

There is a small but non-negligible force resultant to loading disk brakes oriented to eject the
wheel from its dropouts. There have also been cases of QRs releasing inadvertently. Lawyer
lips/conical seating surfaces minimize these possibilities. There has been recent discussion on
Usenet and a link to a website with detailed descriptions of these possibilities and a free-body
diagram of the forces involved.

"Michael" <[email hidden]> wrote in message
"]news:[email hidden]...

Quoted message said:

Quoted message said:

Disk brake bicycles should have conical sunk dropouts so that the up and down forces from road
and brake do not cause motion.

Can you give more detail? I'm having a custom fork made for a disc-brake road bike, so I'd like to
build in whatever safety features I can.

Matt O'Toole <[email hidden]> wrote:

: This is the heart of the issue. Braking converts kinetic energy to heat, which is dissipated into
: the air. Your wheel rims are larger, and have more mass, than any normal disk brake on the market.
: This means they can dissipate heat better, plus they can absorb more heat without becoming
: incredibly hot.

: In fact most disc brakes sold for MTB use become inadequate on long, high speed descents. And
: that's on trails where really high speeds are hardly reached, and not for long, plus the load is
: just a rider -- no heavy touring bags, etc. A fully loaded touring bike on a long, highway descent
: would overheat these brakes very quickly. Special, larger disc brakes are sold for downhill racing
: bikes and tandems --and they're necessary.

Disc brakes seem to have become quite popular among recumbents. At least we'll get a fair trial for
this technology by a reasonable user base in the coming years.

Interesting points you have. Would cheaper disc brakes like Bitex or Logan be even less reliable and
effective?

I've read quite a few comments about how good disc brakes are, like people claiming that theirs
"never fade on long descents". Does that mean recumbent riders don't view their bikes/trikes
rationally? (As if anybody did...)

FWIW, recumbents can be extremely fast on long descents. Also, I consider touring as the
primary application area for recumbents. (Unless maybe you want to count "day rides" as an
application area...)

: The advantages of disc brakes are consistency, modulation, and precision, especially where mud and
: dirt can foul the rims. They give more control, and better threshold braking ability. However, rim
: brakes ultimately have more power, that being defined as the ability to dissipate heat on a long
: descent.

If your assessment is correct, maybe recumbent communities will eventually migrate back from disc
brakes, or then conclude that for most applications one doesn't need the braking power, but it's
nice to have the other benefits instead...

--
Risto Varanka | helsinki.fi~rvarankaOpen ↗ varis at no spam please iki fi

1)are shimano's Intel 4 brake units adaptable to a shimano cassette hub.what's 2)inside an intel 4?
2)is idea one an improvement over a rim setup?
3)are the brake units seperabl;e from the the hub/trans here?

<[email hidden]> wrote in message
"]news:[email hidden]...

Quoted message said:

Matt O'Toole <[email hidden]> wrote:

: This is the heart of the issue. Braking converts

kinetic

Quoted message said:

: energy to heat, which is dissipated into the air. Your wheel rims are larger, and have more
: mass, than any

normal

Quoted message said:

: disk brake on the market. This means they can dissipate heat better, plus they can absorb more
: heat without

becoming

Quoted message said:

: incredibly hot.

: In fact most disc brakes sold for MTB use become

inadequate

Quoted message said:

: on long, high speed descents. And that's on trails

where

Quoted message said:

: really high speeds are hardly reached, and not for long, plus the load is just a rider -- no
: heavy touring bags,

etc.

Quoted message said:

: A fully loaded touring bike on a long, highway descent

would

Quoted message said:

: overheat these brakes very quickly. Special, larger

disc

Quoted message said:

: brakes are sold for downhill racing bikes and

tandems --and

Quoted message said:

: they're necessary.

Disc brakes seem to have become quite popular among

recumbents. At

Quoted message said:

least we'll get a fair trial for this technology by a

reasonable

Quoted message said:

user base in the coming years.

Interesting points you have. Would cheaper disc brakes

like Bitex

Quoted message said:

or Logan be even less reliable and effective?

I'm not familiar with them, so I have no idea. However, if they're similar to the typical MTB-XC
type brakes, they're probably undersized to begin with.

Quoted message said:

I've read quite a few comments about how good disc brakes

are,

Quoted message said:

like people claiming that theirs "never fade on long

descents".

Quoted message said:

Does that mean recumbent riders don't view their

bikes/trikes

Quoted message said:

rationally? (As if anybody did...)

Quoted message said:

FWIW, recumbents can be extremely fast on long descents.

Also, I

Quoted message said:

consider touring as the primary application area for

recumbents.

Quoted message said:

(Unless maybe you want to count "day rides" as an

application

Quoted message said:

area...)

I don't know what disc brakes these recumbent riders are using, or what terrain they're dealing
with. Are they cruising down 500' hills, or hauling ass down 3000'+ mountains with heavy loads? That
makes a difference. Are they using typical MTB-XC disc brakes, or oversized ones with rotors
simlilar in size and mass to a rim (like the ones tandem riders use)?

Quoted message said:

: The advantages of disc brakes are consistency,

modulation,

Quoted message said:

: and precision, especially where mud and dirt can foul

the

Quoted message said:

: rims. They give more control, and better threshold

braking

Quoted message said:

: ability. However, rim brakes ultimately have more

power,

Quoted message said:

: that being defined as the ability to dissipate heat on a long descent.

If your assessment is correct, maybe recumbent communities

will

Quoted message said:

eventually migrate back from disc brakes, or then conclude

that for

Quoted message said:

most applications one doesn't need the braking power, but

it's

Quoted message said:

nice to have the other benefits instead...

My assessment had nothing to do with what brakes recumbents might be using, but what brakes are
commonly available for upright bikes -- MTB brakes.

If recumbent riders are using certain models successfully for high speed descents *with heavy
loads,* then those models should be adequate for a normal touring bike too, since the loads would be
similar. However, adapting a touring bike to use them would involve custom work, which is very
expensive. If you know of a brake that is proven under loads similar to yours, and you don't mind
paying big bucks to have a bike custom-built to use it, then go ahead.

Matt O.

Matt O'Toole <[email hidden]> wrote:
: I don't know what disc brakes these recumbent riders are using, or what terrain they're dealing
: with. Are they cruising down 500' hills, or hauling ass down 3000'+ mountains with heavy loads?
: That makes a difference. Are they using typical MTB-XC disc brakes, or oversized ones with rotors
: simlilar in size and mass to a rim (like the ones tandem riders use)?

Basically recumbents use the same parts as upright bikes, the frame is the custom-built (and very
expensive) part. On mid-range or high-end recumbents, you could see disk brakes like Shimano's M515
or the models from Magura (hydraulic or mechanical). If you wanted more heavy-duty brakes, many
manufacturers would probably be happy to install them.

I'd think most recumbent riders are doing those 500' hills with light load, if even that. (Dutch
people don't have such hills for example.) I don't know which solutions the heavy touring
aficionados have found, but at least there are some bikes (or trikes) built specifically for
heavy touring.

Would it make sense to for example have disc brakes in front and a rim brake in back? You could use
the disc brakes for hard braking when you need control, and the rim brake for bleeding off speed
gradually or for braking when you are going at a slow speed. Also, if you have a trike you could
have three brakes, which might make the load a bit easier. In practice it might be hairy though,
since using a rear brake on a (tadpole) trike could cause it to fishtail :-/

: If recumbent riders are using certain models successfully for high speed descents *with heavy
: loads,* then those models should be adequate for a normal touring bike too, since the loads would
: be similar.

No doubt :-)

: However, adapting a touring bike to use them would involve custom work, which is very expensive.
: If you know of a brake that is proven under loads similar to yours, and you don't mind paying big
: bucks to have a bike custom-built to use it, then go ahead.

Recumbents are very expensive anyway, because production series are very small. Therefore
customization doesn't hurt that much anymore, but it's more likely that a particular model would be
designed to use disc brakes, maybe even some particular type of disc brakes, from the start.

--
Risto Varanka | helsinki.fi~rvarankaOpen ↗ varis at no spam please iki fi

Michael Press said:

Quoted message said:

Disk brake bicycles should have conical sunk dropouts so that the up and down forces from road
and brake do not cause motion.

Quoted message said:

Can you give more detail? I'm having a custom fork made for a disc-brake road bike, so I'd like to
build in whatever safety features I can.

The outer face of the jam nut, the face that presses against the dropout when the QR is secured,
should have a conical face, 45 degree included angle would be best. This cone would mate with a
countersink in a slotted fork dropout. By this means there could be no motion between axle and
dropout unless the axle or QR skewer broke, something that will not reasonably occur. On the other
hand, one cannot drop the wheel out merely by opening the QR. The skewer must be unscrewed partly
after release, the same as with "lawyer lips."

Jobst Brandt [email hidden] Palo Alto CA

Michael said:

Quoted message said:

Disk brake bicycles should have conical sunk dropouts so that the up and down forces from road and
brake do not cause motion.

Can you give more detail? I'm having a custom fork made for a disc-brake road bike, so I'd like to
build in whatever safety features I can.

If you're making a custom fork, have the caliper mount moved from the rear of the left fork leg to
the front of the right fork leg. You can still use a standard caliper, since the hydraulic line or
cable will still exit upwards (but the wrong way if you use the front of the left fork leg). What
was a disengagement force component is now an engagement force component.

The earliest motorcycles with disc brakes had the calipers in front of the forks. I think they were
moved behind to keep the caliper mass nearer the steering axis, and nearer the bike's CG. With no
slotted forks and quick releases, resultant force direction was not an issue.

Conical surfaces require several non-standard parts, and require either spreading the fork legs
slightly on installation or having them compressed slightly in the installed state. This would be OK
for standard forks, but a bad idea for telescopic forks on mountain bikes.

Dave Lehnen

"Dave Lehnen" <[email hidden]> wrote in message "]news:[email hidden]...

Quoted message said:

Conical surfaces require several non-standard parts, and

require

Quoted message said:

either spreading the fork legs slightly on installation or

having

Quoted message said:

them compressed slightly in the installed state. This

would be OK

Quoted message said:

for standard forks, but a bad idea for telescopic forks on

mountain

Quoted message said:

bikes.

There's already an off-the-shelf solution to this problem. Downhill/freeride/whatever MTB forks have
fully captured axles, along with hubs and QRs to match -- such as the Marzocchi QR20 system.
Although a conical dropout interface would be easy enough to make, simply copying Marzocchi's fork
end and using the mating Marzocchi fork parts might be easier and cheaper, depending on the machine
shop you have access to.

But again, I wouldn't touch disk brakes for a touring bike unless I knew the ones being considered
were capable of handling touring loads. I'm not confident that current ones are.

FWIW, any MTB fork I've played with could easily be spread enough to clear conical axle ends.
It wouldn't be convenient, but I don't see it as a problem. This includes the new,
super-stiff Fox Forx.

Matt O.

Disc brakes can outperform rim brakes

1. on a normal bike. The math shown previously about rims having more metal area so more power
dissipation is only partly true. It is true if the brake can get equally hot. But a rim cannot be
allowed to get as hot as a disc rotor. The soft pad of a rim brake (needed for brake
responsiveness) cannot get as hot. And the tyre bead cannot get as hot. A disc rotor can glow red
hot and there is no immediate problem. Look at a car.

2. on a recumbent trike. Disc brakes are the exclusive preferred choice on a tandem recumbent trike.
Long steep decents on these long fast pigs with rim brakes have overheated and exploded the tyres
(true experience from a bent trike manufacturer). Not preferred. With 160mm disc brakes there is
no problem on these big tandem muthas. Other advanteges of disc brakes on the recumbent trike: 1.
With 2 front wheels more braking force is available. 2. With small front wheels disc brakes
become effectively much larger. Yum.

3. someone mentioned drag brakes. Not sure what this means, but if it is the rear drum brakes fitted
to some tandem bikes, these have very poor performance compared to a disc. Much less power, and
when they get hot they fade. Disc brakes don't.

[email hidden] wrote ...

Quoted message said:

Matt O'Toole <[email hidden]> wrote:
: I don't know what disc brakes these recumbent riders are using, or what terrain they're dealing
: with. Are they cruising down 500' hills, or hauling ass down 3000'+ mountains with heavy loads?
: That makes a difference. Are they using typical MTB-XC disc brakes, or oversized ones with
: rotors simlilar in size and mass to a rim (like the ones tandem riders use)?

Basically recumbents use the same parts as upright bikes, the frame is the custom-built (and very
expensive) part. On mid-range or high-end recumbents, you could see disk brakes like Shimano's
M515 or the models from Magura (hydraulic or mechanical). If you wanted more heavy-duty brakes,
many manufacturers would probably be happy to install them.

I'd think most recumbent riders are doing those 500' hills with light load, if even that. (Dutch
people don't have such hills for example.) I don't know which solutions the heavy touring
aficionados have found, but at least there are some bikes (or trikes) built specifically for heavy
touring.

Would it make sense to for example have disc brakes in front and a rim brake in back? You could
use the disc brakes for hard braking when you need control, and the rim brake for bleeding off
speed gradually or for braking when you are going at a slow speed. Also, if you have a trike you
could have three brakes, which might make the load a bit easier. In practice it might be hairy
though, since using a rear brake on a (tadpole) trike could cause it to fishtail :-/

: If recumbent riders are using certain models successfully for high speed descents *with heavy
: loads,* then those models should be adequate for a normal touring bike too, since the loads
: would be similar.

No doubt :-)

[email hidden] wrote in message news:<[email hidden]>...

Quoted message said:

Robert Strickland said:

I followed a thread about disc brakes a while back in which some folks said that they thought
disc brakes didn't make sense on a road bike. The arguments made sense to me. It seems likely
that you'd trade extra hassle, weight and money for no real substantial benefits. What I'm
wondering is if you all think they make sense for loaded touring. I'm planning to have my steel
touring-frame stripped and re-painted and I then plan to build up a (mostly Campy) loaded
touring bike. I was thinking that disc brakes might make sense and since I'm having the frame
repainted I might think about adding disc brake mounts. Any thoughts on this? I should make
clear that I don't have any real knowledge about disc brakes. What would be the pro's and con's
besides better wet or muddy braking and stronger brakes for heavy loads?

You can't put a disc-brake on a conventional fork safely for two reasons, the fork end cannot
withstand the bending moment introduced at it's flimsy narrow end, and if you did use one, the
front wheel would disengage when braking unless you got dropouts with lawyer lips. Hub brakes
introduce bending moments at the dropout similar to those at the fork crown. That is why fork
blades are large and oval at the crown.

You might just go back and read the thread on wheel disengagement of disc-brake bicycles. This
stuff has not been well thought out. Disk brake bicycles should have conical sunk dropouts so that
the up and down forces from road and brake do not cause motion.

Jobst Brandt [email hidden] Palo Alto CA

This time Jobst is right. If you keep trying long enough you'll get it.

Grant Sellek <[email hidden]> wrote:
: Disc brakes can outperform rim brakes

Thanks for the points... something to consider! 🙂

: 3. someone mentioned drag brakes. Not sure what this means, but if it is the rear drum brakes
: fitted to some tandem bikes, these have very poor performance compared to a disc. Much less
: power, and when they get hot they fade. Disc brakes don't.

Hmm wasn't it a rear rim brake operated by a friction gear lever? So you can crank the lever to a
fixed position and have about constant braking force on the rear rim for the whole descent... just
something to take a bit of load from the front brakes.

--
Risto Varanka | helsinki.fi~rvarankaOpen ↗ varis at no spam please iki fi

Grant Sellek said:

Disc brakes can outperform rim brakes

It depends on the criteria by which you judge perform.

Braking force? Nope. On single bikes, for example, brake force is limited by the pitchover point.
Even the lowly single pivot rim brake can produce this much force. On soft surfaces (off-road) the
limit of braking may be even less, limited by tire traction.

Elimination of brake fade? Nope. See below.

Lower weight and cost? Nope.

Quoted message said:

1. on a normal bike. The math shown previously about rims having more metal area so more power
dissipation is only partly true. It is true if the brake can get equally hot. But a rim cannot
be allowed to get as hot as a disc rotor. The soft pad of a rim brake (needed for brake
responsiveness) cannot get as hot. And the tyre bead cannot get as hot. A disc rotor can glow
red hot and there is no immediate problem. Look at a car.

Bicycle disk brakes also can not be allowed to get too hot. They can and do fail due to overheating.
According to some published tests, many models of disk brakes fail at lower power dissipation levels
than tires fail with rim brakes. See the link below for some test results:

ihpva.org023003.htmlOpen ↗

Quoted message said:

2. on a recumbent trike. Disc brakes are the exclusive preferred choice on a tandem recumbent
trike.

The most likely reason that disk brakes are popular for trikes is simply because they are
easier to mount.

Quoted message said:

3. someone mentioned drag brakes. Not sure what this means,

Since you are such an expert on bicycle brakes, it is hard to believe you never heard of a
drag brake.

Quoted message said:

but if it is the rear drum brakes fitted to some tandem bikes, these have very poor performance
compared to a disc. Much less power, and when they get hot they fade. Disc brakes don't.

Drag brakes are not intended as the primary braking device. A drum drag brake is used in
conjunction with rim brakes typically gives better performance than disk brakes. More information
on this can be found at:

tandem-fahren.deDiskFAQ.htmlOpen ↗

Mark McMaster [email hidden]