SRAM Spectro S7 drum brake question.

(Phil) wrote:

Has anyone out there successfully removed the drum brake from a SRAM
S7? I'm wondering if it's possible to shave some weight from this 1700
gram hub.

The spoke hole flange is machined into the brake drum, so that part
must stay.

The brake plate could be removed and a spacer added to the axle, but
the exposed inner drum surface would be subject to rusting.

1700g seems like a lot, but when you subtract from that the weight of
a derailleur or two, a freewheel or cassette, a foot of chain and a
rim brake, it's really not that bad. To put it another way, if you
are bothered by the weight of a nice internal gear hub like that,
you're probably not a gearhub sort of guy anyway.

Chalo Colina

Are youinferring the hub on the S7 roller brake version is made of aluminum or
other lightweight metals?

Yes. I believe the SRAM site indicates that the no-brake and coaster
brake versions are housed in steel, and the drum brake has an aluminum
shell.

-Phil

meb wrote:

I?m seeing one set of specs listing the no brake version being 42 grams
lighter than the roller brake version with the coaster brake
intermediate. Manufactures? web site shows 179 g difference for the 2003
roller brake vs. no-brake S7?s. I would expect the brake to weigh a lot
more than 1 ½ ounces unless it?s a lot simpler than other drum style
brakes. The analogous P5 units are different in weight by 206 g. Are you
inferring the hub on the S7 roller brake version is made of aluminum or
other lightweight metals?

"Roller brake" is Shimano's trade name for their cam-actuated drum
brake. The SRAM hub has a conventional drum brake with one shoe
leading and one trailing.

Every version of the SRAM or Sachs drum braked 7-speed hub I have seen
uses an aluminum shell. Every version I have seen without a brake
uses a steel shell. As a result they weigh almost the same.

Anybody know if that roller brake itself is heavy or light, and if
differing materials are used between the models ?

The drum brake on the S7 hub, being of normal design, has a steel
liner pressed into a cavity in the hub's left flange. The removable
portion is a steel cover plate with the brake shoes, reaction arm, and
actuator arm built in. It is fairly heavily built, but it is also
more integrated into the hub shell than Shimano's spline-attached
brake and thus not nearly as convenient to omit.

BTW: Does anybody have any knowledge of the drive efficiency of the
three S7 brake configurations to each other and also relative
derailleur systems.

I have seen results of some fairly iffy testing on this topic, but I
don't know where to find them posted. The drum-braked and unbraked
models are identical in efficiency, with the coaster perhaps a little
behind them due to brake drag (but not due to gearbox differences).
All of them, in my experience, are less draggy than the Shimano Nexus
7 hub with or without a brake.

Chalo Colina

On 11 Sep 2003 18:33:46 -0700, (Chalo) may
have said:

1700g seems like a lot, but when you subtract from that the weight of
a derailleur or two, a freewheel or cassette, a foot of chain and a
rim brake, it's really not that bad. To put it another way, if you
are bothered by the weight of a nice internal gear hub like that,
you're probably not a gearhub sort of guy anyway.

Or if you're at the other end of the equation, and don't care about
weight, there's the DualDrive setup that combines a 9 speed derailleur
with a multispeed hub. I keep wondering if Sheldon Brown is going to
take one of those and shoehorn it into a bike that has one of the rare
old 5-speed front ders. Hey, even a 3-ring der would produce an
81-speed setup!

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Sorry about the Shimano vs. SRAM tradename mixup on "Rollerbrake".

Checked several old manuals online. The 181g difference seems consistent
and appears the correct difference.

For my application, I wasn't ought for a great number of gears. Just
looking for the most reliable and efficient choise, particularly since
my early plans had the fwd of the recumbent delta with the front wheel
in front of crank (changed in deference to a lighter simpler suspension
practical for swb configuration only). I do have a dual drive on a bent.

With a 700 front, I didn't have any ratio problems, just efficiency and
reliability concerns. There seems some data out there to suggests
deraileurs may have a slight efficiency advantage, but I no S7 data.

I personally would like to keep the onboard brake since I need one
anyway like Chalo pointed out. Coaster brake would leave witth foot
control of the front brake and lever control of each rear, but at a
currently unquantified efficiency loss. If I cant's get data, I'll
probably go drum and set that lever under thumb control.



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