On 2019-03-14 18:36, 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.


I think the common sweet spot concensus is 25mm which is what I am
riding right now. Though I'd rather have 32mm in back for CX capability
but unfortunately the frame isn't built for that.


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.


That I don't understand. Even the early 80's Shimano 600 set on my road
bike has little release handles on each caliper to get out a 25mm+ wheel
with lots of room to spare.


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.


Though a disc does get bent easily and you have to pay more attention
when re-installing a wheel. Fixing is easy as well as long as you do not
touch the disc with bare hands.


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.


This falls under the category "Don't do that!" :-)


... That's a detriment, but doesn't affect cable
actuated disc brake callipers.

Hydraulic disc callipers are self adjusting like car hydraulic disc
callipers. ...


Ahm, sort of. The reservoirs are typically a bit small to accommodate
all the wear. I have to top off with DOT-4 at times which is nasty stuff
when it gets onto clothes and things.


Cable actuated disc callipers are not. Benefit and detriment.


Cable calipers are very easy to adjust, just turn a knurled trim knob. A
downside of many is that they only have one moving piston while the
opposite piston is fixed. The rotor flexes to the side every time you
brake. Beats me why they design them that way.


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.


IME it's needed once a year at the most. But when it's needed it really
is and not doing it can result in a bad crash.


... 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.


The cable discs I used just don't have the same kind of stopping power
with modest lever force as hydraulic disc brakes.


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


I can't confirm that one. My road bike with rim brakes is just as good
in modulating stopping power as my MTB with hydraulic disc brakes.
UNLESS ... it rains a lot. Then it has zero stopping power for a
sometimes gut-churning 1-2sec.


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.


Plus it's a whole lot cheaper and the replacement job takes a couple of
minutes versus the better part of a Saturday morning.


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


I was sold on disc brakes after about five seconds of use. When I almost
flew over the handlebar of my new MTB during a test ride in the LBS
parking lot, despite having pulled the handle with just two fingers. The
rear of the MTB actually bucked upwards. It felt like having
power-assist brakes. Woohoo!


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.


I do. Should I ever need a new road bike it will have discs or I won't buy.

--
Regards, Joerg

http://www.analogconsultants.com/