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Old March 15th 19, 02:23 PM posted to rec.bicycles.tech
Ralph Barone[_4_]
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Posts: 385
Default The death of rim brakes?

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.
YMMV.

And, of course, a disc brake is heavier than a rim brake :-)


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.

--
Cheers,
John B.


With cantis and V-brakes, you may still have to disconnect the straddle
wire or deflate your tire to remove the wheel. And if the brake pads sit
inside the fork, they will limit how wide of a tire you can install, while
disc brakes won't.

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