The death of rim brakes?

On Friday, March 15, 2019 at 6:23:52 AM UTC-7, Ralph Barone wrote:
John B. Slocomb wrote:
On Fri, 15 Mar 2019 15:24:05 +1100, James
wrote:

On 15/3/19 1:50 pm, John B. Slocomb wrote:
On Fri, 15 Mar 2019 12:36:42 +1100, James
wrote:

On 15/3/19 2:17 am, Frank Krygowski wrote:
On 3/13/2019 6:32 PM, Joerg wrote:
On 2019-03-12 11:13, AMuzi wrote:

How many new bicycles have drum brakes? Vanishingly few.


This was just meant as an example. Bicycles have largely remained in
the stone age, like chuck wagons where a chunk of wood pressed against
the steel ring of the wheels to brake. So bicycles kind of skipped a
technology.

Bikes didn't skip drum brake technology because bikes are primitive..
Only a very few bikes adopted drum brakes because that technology wasn't
optimum for bikes.

It's simplistic at best to pretend what's best for one application is
best for all applications. Every design choice comes with benefits and
detriments, and those are not the same for a 4000 pound car as for a 20
pound bike.

Bicycle rim brakes have worked fine for over 99.999% users for the past
100+ years. When mountain bikes came into fashion, some off-roaders
found a different set of benefits vs. detriments, and discs made sense
for them. But then fashion and marketing took over, pushing discs toward
road bikes.

Yes, we'll get a few testimonials here claiming discs are "better." We
get very few details on benefits vs. detriments.



For a while, the trend for road bikes was very narrow tyres pumped up to
very high pressure. 18 mm of tyre is pretty skinny.

Gradually the tyre width had become standard at 23 mm for road bikes..

Now there is an emerging trend to ride wider tyres, with some claiming
much wider tyres are not only as fast but faster! I suspect there is a
diminishing return with wind resistance.

Now I use a 25 mm rear tyre (that measures 27 mm), and to remove the
wheel I must release the brake lever (Campagnolo) or deflate the tyre.
With a 23 mm tyre I don't need to do that. With a disc brake I don't
need to fiddle with the brakes regardless of tyre width. That's a benefit.

In fact sometimes when you go to shove a wheel in with rim brakes and
centre or dual pivot callipers, you can catch the calliper and move it
from centred. Then you have to fix that or have rubbing brakes. That
doesn't happen with discs.

It is possible with hydraulic disc callipers to squeeze the brake lever
while the wheel is out, and then have trouble moving the pads apart
again to insert the wheel. That's a detriment, but doesn't affect cable
actuated disc brake callipers.

Hydraulic disc callipers are self adjusting like car hydraulic disc
callipers. Cable actuated disc callipers are not. Benefit and detriment.

Hydraulic disc systems sometimes need bleeding. This requires either a
visit to a shop or a bit more kit ($30 - $50) for the home maintenance
person. Detriment. Probably not good if you are out on a tour. Cables
are probably more reliable. Cable operated discs work fine, and there
are also cable/hydraulic systems, where the calliper is hydraulic and
self adjusting, and actuated via a cable.

Disc brake modulation is generally better. That is you can hold the
point of not quite skidding more easily. Benefit.

Disc brakes tend to work better in wet weather, or IOW, work the same
regardless of wet weather. Rim brakes rarely work as well when the rims
are wet.

Rim brakes on carbon fibre rims has never been a happy marriage, but
with disc brakes that problem is eliminated. Thus aerodynamic, strong,
stiff, light weight rims are now easier to manufacture and use - made of
carbon fibre.

Rim brakes do erode rims. Disc brakes do not. I guess the disc rotor
will wear out, but I'd rather replace a rotor than a rim.

It seems to me that many people try disc brakes and find few drawbacks.
That's just my opinion, unsubstantiated by statistics.

Are rim brakes good enough? Sure! They have been for a long time. Are
disc brakes better? Yes I think so. Not outstandingly, but better.
I'm not about to have my road bike modified to take disc brakes, and I
wouldn't let the choice of brakes on a new bike dictate what I bought.

On Fri, 15 Mar 2019 17:22:58 +1100, James
wrote:

On 15/3/19 5:01 pm, John B. Slocomb wrote:
On Fri, 15 Mar 2019 11:57:26 +0700, John B. Slocomb
wrote:

On Fri, 15 Mar 2019 15:24:05 +1100, James
wrote:

On 15/3/19 1:50 pm, John B. Slocomb wrote:
On Fri, 15 Mar 2019 12:36:42 +1100, James
wrote:

On 15/3/19 2:17 am, Frank Krygowski wrote:
On 3/13/2019 6:32 PM, Joerg wrote:
On 2019-03-12 11:13, AMuzi wrote:

How many new bicycles have drum brakes? Vanishingly few.


(MUCH DELETED)

And rim brake callipers that go around fat tyres often flex a lot and
don't work so well. So disc brakes for fat tyre bikes are a better
choice, and rim brakes for racing bikes with skinny tyres are pretty good.

Don't use calipers. Try cantilever or the more modern Shimano
V-brakes. They don't care how wide the tire is.

As an addendum: While cheaper they do look a bit low budget so, as one
might say, who would one want a $10 brake on a $3,000 bicycle... even
if they do stop well :-)


I've had canti brakes on a MTB. Yes the rims took a hammering.

It comes to mind that as the braking resistance is applied at the
contact of the tire and the road and that the resistance is applied to
the wheel hub that a much stronger disc brake wheel would be required
than when using a rim brake as the ratio between the disc brake disc
and the contact with the road is approximately 26.5"/7.5" (average 2
sizes of disc rotor) = about 3.5 ratio while a rim brake is only about
an inch and a half difference so say 26.5/23.5=1.1 ratio. Based on
braking forces it would appear that a disc brake wheel would have to
be roughly 3 times stronger than a rim brake wheel.

36 spoke, cross three, wheels anyone?

But of course an ATB is already so heavy that the addition of strong
wheels is rather a matter of bringing coals to Newcastle.

--
Cheers,
John B.

On Friday, March 15, 2019 at 4:32:23 PM UTC-7, John B. Slocomb wrote:
On Fri, 15 Mar 2019 17:22:58 +1100, James
wrote:

On 15/3/19 5:01 pm, John B. Slocomb wrote:
On Fri, 15 Mar 2019 11:57:26 +0700, John B. Slocomb
wrote:

On Fri, 15 Mar 2019 15:24:05 +1100, James
wrote:

On 15/3/19 1:50 pm, John B. Slocomb wrote:
On Fri, 15 Mar 2019 12:36:42 +1100, James
wrote:

On 15/3/19 2:17 am, Frank Krygowski wrote:
On 3/13/2019 6:32 PM, Joerg wrote:
On 2019-03-12 11:13, AMuzi wrote:

How many new bicycles have drum brakes? Vanishingly few.


(MUCH DELETED)

And rim brake callipers that go around fat tyres often flex a lot and
don't work so well. So disc brakes for fat tyre bikes are a better
choice, and rim brakes for racing bikes with skinny tyres are pretty good.

Don't use calipers. Try cantilever or the more modern Shimano
V-brakes. They don't care how wide the tire is.

As an addendum: While cheaper they do look a bit low budget so, as one
might say, who would one want a $10 brake on a $3,000 bicycle... even
if they do stop well :-)


I've had canti brakes on a MTB. Yes the rims took a hammering.

It comes to mind that as the braking resistance is applied at the
contact of the tire and the road and that the resistance is applied to
the wheel hub that a much stronger disc brake wheel would be required
than when using a rim brake as the ratio between the disc brake disc
and the contact with the road is approximately 26.5"/7.5" (average 2
sizes of disc rotor) = about 3.5 ratio while a rim brake is only about
an inch and a half difference so say 26.5/23.5=1.1 ratio. Based on
braking forces it would appear that a disc brake wheel would have to
be roughly 3 times stronger than a rim brake wheel.

36 spoke, cross three, wheels anyone?

But of course an ATB is already so heavy that the addition of strong
wheels is rather a matter of bringing coals to Newcastle.

My disc wheels haven't exploded so far, and I've been riding home-built disc wheels on cheap hubs (M525 or SP PD8 dyno) and relatively cheap rims (CR 18 or now out of production Velocity touring disc) for about 15 years. I even have a Vuelta el-cheapo disc that has held up well. I bought the first generation Cannondale CADDX CX bike with discs before they were UCI legal for cyclocross -- which is why I dropped out of racing CX as a pro in Europe. If they wouldn't accept my brakes, I wasn't going to race there. It has been my commuter for years, along with its replacement (yes, I broke the original frame -- broken frame number 7(? could be more)). My other bikes with disc wheels are doing fine, too.

-- Jay Beattie.

On 16/3/19 10:32 am, John B. Slocomb wrote:


It comes to mind that as the braking resistance is applied at the
contact of the tire and the road and that the resistance is applied to
the wheel hub that a much stronger disc brake wheel would be required
than when using a rim brake as the ratio between the disc brake disc
and the contact with the road is approximately 26.5"/7.5" (average 2
sizes of disc rotor) = about 3.5 ratio while a rim brake is only about
an inch and a half difference so say 26.5/23.5=1.1 ratio. Based on
braking forces it would appear that a disc brake wheel would have to
be roughly 3 times stronger than a rim brake wheel.

36 spoke, cross three, wheels anyone?

But of course an ATB is already so heavy that the addition of strong
wheels is rather a matter of bringing coals to Newcastle.


Well, you don't build a disc brake wheel with radial spokes.


--
JS

On Sat, 16 Mar 2019 18:57:21 +1100, James
wrote:

On 16/3/19 10:32 am, John B. Slocomb wrote:


It comes to mind that as the braking resistance is applied at the
contact of the tire and the road and that the resistance is applied to
the wheel hub that a much stronger disc brake wheel would be required
than when using a rim brake as the ratio between the disc brake disc
and the contact with the road is approximately 26.5"/7.5" (average 2
sizes of disc rotor) = about 3.5 ratio while a rim brake is only about
an inch and a half difference so say 26.5/23.5=1.1 ratio. Based on
braking forces it would appear that a disc brake wheel would have to
be roughly 3 times stronger than a rim brake wheel.

36 spoke, cross three, wheels anyone?

But of course an ATB is already so heavy that the addition of strong
wheels is rather a matter of bringing coals to Newcastle.


Well, you don't build a disc brake wheel with radial spokes.

But they do built a rim brake wheel with radial spokes }-)

I think that if I were riding around in the mud and mire I probably
would want discs but I don't do that. Anywhere that I want to go has
paved roads leading to it.

I find it rather revealing that in 1880 the League of American
Wheelmen, a bicycle advocate group, was formed and one of the first
things that they lobbied for was smooth roads. Now that smooth roads,
in the U.S. at least, probably make up the majority of the roads
people have discovered riding out in the bush where there hardly
aren't any roads at all.

I suppose that the moral is that once a bicyclist finally gets
something they immediately want something different :-}

--
Cheers,
John B.

with John B Slocomb wrote:
On Fri, 15 Mar 2019 15:24:05 +1100, James
wrote:

*SKIP*
And rim brake callipers that go around fat tyres often flex a lot and
don't work so well. So disc brakes for fat tyre bikes are a better
choice, and rim brakes for racing bikes with skinny tyres are pretty
good.
Don't use calipers. Try cantilever or the more modern Shimano
V-brakes. They don't care how wide the tire is.

Of course they (v-brakes) do. My success story.

My prefered LBS (at the moment, they've changed their ways) had really
brain-dead parking -- right triangle from side-view, with very narrow
parking holes, with maybe 30cm height. My 700Cx49 just couldn't
possibly fit in. What effectively disabled me from reaching (with 180cm
cable) front wheel.

So, one day, I park with this abomination, do my LBS stuff, unpark, and
ride away. And then over each change in road's smoothness (natural or
not) I detect some unusual sound. That made me wonder. At some point I
had to go on a curb, so I was looking around front wheel and then,..

Holy Chain! As I lift fork I see front wheel droping out dropouts
(quick-release had been involved), is blocked by v-brakes, hits a
sidewalk, and is placed back into dropouts.

I speculate that some random dude (with evil intentions) undid
quick-release as this bike was parked and had found out he had to
release v-brakes, then exhaust tyre, and only then he could possibly
labour the wheel out (because neither releasing nor exhausting help
much, these steps just enable). And getting real dirty on the way.

That's how V-Brakes Save The Day!

p.s. Also, example of proper quoting.

--
Torvalds' goal for Linux is very simple: World Domination
Stallman's goal for GNU is even simpler: Freedom

James wrote:
On 16/3/19 10:32 am, John B. Slocomb wrote:


It comes to mind that as the braking resistance is applied at the
contact of the tire and the road and that the resistance is applied to
the wheel hub that a much stronger disc brake wheel would be required
than when using a rim brake as the ratio between the disc brake disc
and the contact with the road is approximately 26.5"/7.5" (average 2
sizes of disc rotor) = about 3.5 ratio while a rim brake is only about
an inch and a half difference so say 26.5/23.5=1.1 ratio. Based on
braking forces it would appear that a disc brake wheel would have to
be roughly 3 times stronger than a rim brake wheel.

36 spoke, cross three, wheels anyone?

But of course an ATB is already so heavy that the addition of strong
wheels is rather a matter of bringing coals to Newcastle.


Well, you don't build a disc brake wheel with radial spokes.



I missed commenting to John earlier. Your visualization of the problem
isn't quite right. With rim brakes, the spokes do not see any braking
forces, since the brakes sit between the spokes and the tire. No matter
what size of disc brake you have, the spoke forces are the same, since the
braking force is applied to the hub, which then transfers it through the
spokes to the rim/tire. In the limit, the hub is stationary and the wheel
is sliding. In this case, the size of the disc determines how much
tangential force is applied to the disc, but the force on the spokes is
determined by the number of spokes, the lacing pattern and the hub
diameter.

John B. Slocomb wrote:
On Sat, 16 Mar 2019 18:57:21 +1100, James
wrote:

On 16/3/19 10:32 am, John B. Slocomb wrote:


It comes to mind that as the braking resistance is applied at the
contact of the tire and the road and that the resistance is applied to
the wheel hub that a much stronger disc brake wheel would be required
than when using a rim brake as the ratio between the disc brake disc
and the contact with the road is approximately 26.5"/7.5" (average 2
sizes of disc rotor) = about 3.5 ratio while a rim brake is only about
an inch and a half difference so say 26.5/23.5=1.1 ratio. Based on
braking forces it would appear that a disc brake wheel would have to
be roughly 3 times stronger than a rim brake wheel.

36 spoke, cross three, wheels anyone?

But of course an ATB is already so heavy that the addition of strong
wheels is rather a matter of bringing coals to Newcastle.


Well, you don't build a disc brake wheel with radial spokes.

But they do built a rim brake wheel with radial spokes }-)


Certainly. But only for front wheels, since rear wheels have accelerating
torque applied through the spokes, regardless of the braking method.

I think that if I were riding around in the mud and mire I probably
would want discs but I don't do that. Anywhere that I want to go has
paved roads leading to it.

I find it rather revealing that in 1880 the League of American
Wheelmen, a bicycle advocate group, was formed and one of the first
things that they lobbied for was smooth roads. Now that smooth roads,
in the U.S. at least, probably make up the majority of the roads
people have discovered riding out in the bush where there hardly
aren't any roads at all.

I suppose that the moral is that once a bicyclist finally gets
something they immediately want something different :-}

--
Cheers,
John B.

On 16/3/19 7:38 pm, John B. Slocomb wrote:
On Sat, 16 Mar 2019 18:57:21 +1100, James
wrote:

On 16/3/19 10:32 am, John B. Slocomb wrote:


It comes to mind that as the braking resistance is applied at the
contact of the tire and the road and that the resistance is applied to
the wheel hub that a much stronger disc brake wheel would be required
than when using a rim brake as the ratio between the disc brake disc
and the contact with the road is approximately 26.5"/7.5" (average 2
sizes of disc rotor) = about 3.5 ratio while a rim brake is only about
an inch and a half difference so say 26.5/23.5=1.1 ratio. Based on
braking forces it would appear that a disc brake wheel would have to
be roughly 3 times stronger than a rim brake wheel.

36 spoke, cross three, wheels anyone?

But of course an ATB is already so heavy that the addition of strong
wheels is rather a matter of bringing coals to Newcastle.


Well, you don't build a disc brake wheel with radial spokes.

But they do built a rim brake wheel with radial spokes }-)

Yes, I use some I built. It's mostly a fashion thing. The weight
reduction by shorter spokes isn't worth worrying about.

In most cases a regular 3x spoke wheel is sufficient to transfer brake
forces from the hub to the rim.

Imagine the possible force on spokes possible from a 28 tooth chain ring
to a 34 tooth rear sprocket?


I think that if I were riding around in the mud and mire I probably
would want discs but I don't do that. Anywhere that I want to go has
paved roads leading to it.

I find it rather revealing that in 1880 the League of American
Wheelmen, a bicycle advocate group, was formed and one of the first
things that they lobbied for was smooth roads. Now that smooth roads,
in the U.S. at least, probably make up the majority of the roads
people have discovered riding out in the bush where there hardly
aren't any roads at all.


Where I live there are hundreds of kms of gravel roads that are too
rough for my road bike (I've tried). Where as my options are limited by
bitumen only roads. Only the main connecting roads are bitumen, and
they are high speed roads where drivers dislike passing cyclists safely.

I think that people have realised that there are many unmade roads to
explore, and there are few cars on them to worry about.

--
JS

On 17/3/19 2:56 am, Ralph Barone wrote:

I missed commenting to John earlier. Your visualization of the problem
isn't quite right. With rim brakes, the spokes do not see any braking
forces, since the brakes sit between the spokes and the tire.

The spokes may not see any torque between the hub and rim, but are
certainly forces due to braking that the spokes see.

--
JS