SRAM Spectro S7 drum brake question.

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?

Obviously we have either misprinted weights or dated weight figures (such as differing model years).

Anybody know what the current difference in S7 freewheeling vs. the S7 rollerbrake versions is, and whether we are looking a differing model years, materials, or what as the source of the conflicting figures.

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

I am intending to use the S7 in a recumbent build.

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

(Phil) said:

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

Quoted message said:

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 said:

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.

Quoted message said:

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.

Quoted message said:

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

(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!

--
My email address is antispammed; pull WEEDS if replying via e-mail. Yes, I have a killfile. If I
don't respond to something, it's also possible that I'm busy.

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.