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Roller brakes: running friction?



 
 
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  #11  
Old June 28th 05, 02:49 AM
David L. Johnson
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Default Roller brakes: running friction?

On Tue, 28 Jun 2005 05:59:14 +0800, usualsuspect wrote:

the guy in the shop said hub brakes are better anyway.

are you saying this isn't true?


Depends on what you mean. They don't lose stopping ability in the rain,
as many rim brakes/pads do. They last much longer. But in dry conditions
they do not stop as well, and there is the weight and residual drag.


what about hub gears (nexus 8) vs regular derailleurs (shimano deore)?


Same sort of comments apply. They are less prone to
damage/fouling/fussiness than derailleurs, but adjustment is critical, and
they are less efficient.

I use a roller brake and a nexus-7 hub gear on my rain bike. Makes sense
for that.

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David L. Johnson

__o | You will say Christ saith this and the apostles say this; but
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  #12  
Old June 28th 05, 04:07 AM
BJ
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Default Roller brakes: running friction?

Alex Rodriguez wrote in
I agree about the disturbingly gradual buildup of stopping power in the
shimano roller rear brake (no clutch there, unlike the front). My bike
has cantilever bosses, so I kept the 7 spd hub but went back to v-brakes.
And that's one less cable to disconnect to get the wheel off as well. The
thing is packed with grease inside, and I think that contributed to the
rather draggy feel. Maybe it was just due to shedding the weight, but I
gained pretty much one gear on the hills of my commute after ditching it
(I got the thing in the first place as it seemed a reasonable idea for
all-weather commuting in a rainy climate).

:

In article ,
says...

As another poster observes, you don't get disc brake standard instant
stopping with hub brakes but it is more than perfectly adequate.


Adquate for what? I have a Nexus 7 and I can grab the brake till it
touches the bar and it only slows the bike down a bit. An adequate
brake should be able to lock up the wheel. If my bike had cantilever
studs I would have gotten rid of this brake. Especially since I just
found out the brake weighs over a pound.
-----------------
Alex


  #13  
Old June 28th 05, 09:06 AM
Simon Brooke
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Default Roller brakes: running friction?

in message , lid
') wrote:

what about hub gears (nexus 8) vs regular derailleurs (shimano
deore)?


Hub gears typically have /slightly/ more drag than deraileurs but
require /much/ less maintenance. Consequently for a non-racing urban
bike they make a lot of sense.

--
(Simon Brooke) http://www.jasmine.org.uk/~simon/

to err is human, to lisp divine
;; attributed to Kim Philby, oddly enough.

  #17  
Old June 29th 05, 10:09 AM
merryfreakinxmas
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Default Roller brakes: running friction?


"Clive George" wrote in message
...
"Alex Rodriguez" wrote in message
...

Adquate for what? I have a Nexus 7 and I can grab the brake till it
touches
the bar and it only slows the bike down a bit. An adequate brake should
be
able to lock up the wheel.


Apply the front brake sufficiently and it will be able to :-)

Seriously, the back brake shouldn't be doing much of the slowing anyway,
so being a bit crap isn't much of a problem. Unless the front brake is
also crap.

(This does not apply to tandems :-) )


or long wheel based recumbents

Alex
Have you tried taking up the slack in the cable so the lever will not touch
the bar?

cheers,
clive





  #18  
Old June 29th 05, 05:56 PM
Alex Rodriguez
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Default Roller brakes: running friction?

In article 7ztwe.99435$9A2.35907@edtnps89,
says...

Alex
Have you tried taking up the slack in the cable so the lever will not touch
the bar?


Yes I have. The rear brake still can't lock up the rear wheel.
---------------
Alex


  #19  
Old June 29th 05, 09:16 PM
Sheldon Brown
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Default Roller brakes: running friction?

Somebody wrote:

i am looking at a ridgeback switch at the moment.
i was trying to get one with disk brakes but they're out of stock.
the guy in the shop said hub brakes are better anyway.


Alex Rodriguez plied again:

No, the Nexus roller brakes are quite poor. For a rear brake it is not a
big deal. I would not ride a bike that had a front brake that is as poor as
the rear roller brakes are. I

Me neither, but as it happens, the front Rollerbrake is considerably
_worse_ than the rear!

Shimano puts a slip clutch into their Rollerbrake front hubs as a
putative "safety" feature.

Seems a bit bizarre to me that a device that reduces braking power could
be considered a "safety
feature" though.

Some, but not all, Nexus front Rollerbrakes have annoying rattles in the
cable linkage.

what about hub gears (nexus 8) vs regular derailleurs (shimano deore)?


The Nexus 8 is supposed to be better than the Nexus 7.


That's true, I own a Nexus 7 and two Nexus 8s. I just LOVE the Nexus 8,
commuted on one of them this morning...

(I left the Rollerbrakes off of all three of my Nexus bikes, don't need
a weak rear brake that weighs a pound and a quarter. I use rim brakes
on all three of these bikes.

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  #20  
Old June 30th 05, 04:35 PM
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Default Roller brakes: running friction?

Sheldon Brown wrote:
Seems a bit bizarre to me that a device that reduces
braking power could be considered a "safety feature" though.


I have no objection to the concept of modifying torque or preventing
skidding. ABS does both and is considered a safety feature.

I am only concerned about the implementation. ABS modifies torque if
vehicle motion exceeds wheel motion and operates low or high friction
surfaces. The Shimano system merely puts an upper limit on torque.

Shimano quotes ISO 4120 and DIN 79100-2. This requires a weight of 100
kg and a brake lever force of 100 N. I understand that the requirement
is to exceed 2.2 m/s^2 wet and 3.4 m/s^2 dry.

Shimano quotes a deceleration capability of 3 m/s^2 for the SG-8c20
rear hub. Magura claims rim brakes can achieve 4 m/s^2 and discs 8
m/s^2. It would be interesting to know the torque or deceleration
values for the Shimano front hub.

 




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