On 3/14/2019 8:36 PM, 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. YMMV.


So a rear hydraulic disc is just as good as a fixed gear
wheel (without the warped rotor thing). Check.

--
Andrew Muzi
www.yellowjersey.org/
Open every day since 1 April, 1971