Roller brakes: running friction?

Quoted message said:

Shimano says the following about their roller brakes: "Inter-M brake
is different from conventional brakes in that the inside of the brake
drum is filled with grease. This may cause the turning of the wheel
to be slightly heavier than usual, particularly in cold weather"

1. So they have running friction. Does anybody know anything more
about this?

Friction hasn't been a problem with the Shimano Nexus 7 roller brake that
I have some experience of, at least not in London's winters (which aren't
all that cold). The Inter-M roller brake is probably similar or better.
Special grease is available to add via a port, by the way.

Much more of an issue is the amount of drag in the actual hub gear system.
Hopefully that's been improved in the Inter-M.

Quoted message said:

2. They say that there should be 15 mm of play in the brake lever.
That is a lot of movement. Perhaps the gap between pad and drum needs
to be large to reduce the drag caused by the grease in the gap. Is
that the reason?

I suppose so, but the play is only apparent when rocking a stopped bike
back and forth with the brake on. You don't notice it when braking
normally.

~PB

I said:

Quoted message said:

2. They say that there should be 15 mm of play in the brake lever.
That is a lot of movement. Perhaps the gap between pad and drum needs
to be large to reduce the drag caused by the grease in the gap. Is
that the reason?

I suppose so, but the play is only apparent when rocking a stopped
bike back and forth with the brake on. You don't notice it when
braking normally.

Sorry, I misunderstood what "play" you were referring to (there is some
fore & aft play too). I would what Shimano are talking about: "lever
travel".

Quoted message said:

Quoted message said:

That is a lot of movement. Perhaps the gap between pad and drum needs
to be large to reduce the drag caused by the grease in the gap. Is
that the reason?

Yes indeed.

Don't expect it to be a powerful brake! Advantages, though: reduced
cleaning and maintenance, zero rim wear, no need to have rim perfectly
true.

~PB

Quoted message said:

Shimano says the following about their roller brakes: "Inter-M brake is
different from conventional brakes in that the inside of the brake drum
is filled with grease. This may cause the turning of the wheel to be
slightly heavier than usual, particularly in cold weather"

Having ridden on these hubs for over a year, I'm fairly happy that any
effect is minimal and maybe only psychological. If I hadn't read the
Shimano website, I would be blissfully unaware of any theoretical
slowdown in cold weather.

Quoted message said:

1. So they have running friction. Does anybody know anything more about
this?

I took the front wheel off did some comparative spinning with a
conventionally hubbed wheel. There wasn't a significant difference.

Quoted message said:

2. They say that there should be 15 mm of play in the brake lever. That
is a lot of movement. Perhaps the gap between pad and drum needs to be
large to reduce the drag caused by the grease in the gap. Is that the
reason?

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

My only dislike about the set up is that you can't /see/ anything. I get
these paranoid moments when I become convinced the brakes are dragging
and out of adjustment. With conventional brakes, a quick glance tells me
that no, it's not the brakes, it's me that is dragging and out of
adjustment.

Thanks for the replies. By 'play' I meant 'lever travel'. More quotes
from Shimano:

"Turn the cable adjusting bolt of the brake unit or brake lever so that
there is about 15 mm of play in the brake lever."

"The amount of movement in the inner cable must be 14.5 mm or more when
the brake lever is depressed. If it is less than 14.5 mm, braking
performance will suffer, and the brakes may fail to work."

Perhaps that last sentence indicates that:
friction -> heat -> reduced performance

"If you apply the front Inter-M brake strongly while the bicycle is
stopped and then shake the wheel, you will notice that there is a small
amount of play in the brakes. This is normal, and will not cause any
problems at all while riding."

"The front Inter-M brake has a built-in power modulator which controls
the braking force applied to the hub. Noise is generated by the
operation of the power modulator when the brake is applied, but this is
not a sign of a malfunction."

Curiouser and curiouser.

In article <[email hidden]>,
[email hidden] says...

Quoted message said:

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

Alex Rodriguez said:

An adequate brake should be able to lock up the wheel.

Shimano says that the power modulator (a clutch) in the brake "prevents
the wheel from locking-up if the brake force is getting too strong."

See their picture at:
http://cycle.shimano-eu.com/publish/content/cycle/seh/nl/en/technical_service/faq_s/city_and_comfort_bike/how_does_the_power.html

In uk.rec.cycling Alex Rodriguez said:

In article <[email hidden]>,
[email hidden] says...

Quoted message said:

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.

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.

are you saying this isn't true?

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

"Alex Rodriguez" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

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 [censored] isn't much of a problem. Unless the front brake is also
[censored].

(This does not apply to tandems :-) )

cheers,
clive

Clive George said:

"Alex Rodriguez" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

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 [censored] isn't much of a problem.

Agreed.

Quoted message said:

Unless the front brake is also [censored].

Roller brakes can be used up front as well. It's one way to make you ride
extremely carefully, I suppose ;-)

~PB

usualsuspect said:

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.

Quoted message said:

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.

--

David L. Johnson

__o | You will say Christ saith this and the apostles say this; but
_`\(,_ | what canst thou say? -- George Fox.
(_)/ (_) |

Alex Rodriguez <[email hidden]> 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).

news:[email hidden]:

Quoted message said:

In article <[email hidden]>,
[email hidden] says...

Quoted message said:

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

in message <[email hidden]>, [email hidden]

(') said:

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.

--
[email hidden] (Simon Brooke) http://www.jasmine.org.uk/~simon/

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

In article <[email hidden]>, [email hidden] says...

Quoted message said:

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.

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

Quoted message said:

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

The Nexus 8 is supposed to be better than the Nexus 7. I regualrly ride a
Nexus 7 and I can feel the difference between it and a derailleur bike. I
am aware of this, but I like have the drivertrain in the hub shell, less
maintenance. My commute is short, so it is not a big deal.
---------------
Alex

In article <[email hidden]>, [email hidden] says...

Quoted message said:

Alex Rodriguez <[email hidden]> 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).

Maybe Shimano will come out with a disk brake that will work with the Nexus
hub. That would be ideal. My front brake is a Avid disk brake and it works
well in all weather conditions.
----------------
Alex

In article <[email hidden]>,
[email hidden] says...

Quoted message said:

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 [censored] isn't much of a problem. Unless the front brake is also
[censored].

Quite true, and the reason I still have this set up. My front brake is an Avid
mechanical disk brake and it has plenty of stopping power in all conditions.
------------------
Alex

"Clive George" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

"Alex Rodriguez" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

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 [censored] isn't much of a problem. Unless the front brake is
also [censored].

(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?

Quoted message said:

cheers,
clive

In article <7ztwe.99435$9A2.35907@edtnps89>, [email hidden]
says...

Quoted message said:

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

Somebody said:

Quoted message said:

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:

Quoted message said:

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.

Quoted message said:

Quoted message said:

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

Quoted message said:

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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Sheldon Brown said:

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.