ChiapasFixed

So I’m thinking of this hub for my Swift build. It’s the 177% SA 3 speed with a 9 speed cassette. I need a low gear of around 18” and it seems like this will give it to me along with plenty of high range. Any reason not to do this? Anybody have experience with these hubs? Thanks!

Ron Damon

I used a similar SRAM DualDrive3 with an 11-36T, 10-speed cogset for about four years, and it was great but for the weight. Ultimately that was why I sold it. Here it was on tour in Taiwan.

ChiapasFixed

wow nice ride!
I am familiar with the Sram Dual drive from a Bike Friday my wife used to own.
unfortunately it has been discontinued.
im wondering if the SA version is similar, worse/better?

and specifically if it can handle the 18 gear inch low.

jfouellette

My Bike Friday has an old Sachs 3x7 dual drive. Sram bought this company and eventually shut it down. I find this set up quite effective with a wide range of gears while avoiding large cassettes which is important with smaller wheels and no need for a front derailleur. No issue with cross chain also although with 9 gears I don t know.


6

ChiapasFixed

yes I agree it’s a great setup for getting 500%+ range on folders without the drawbacks of a Rolhoff, or a traditional 2x9 or similar setup.

Bike Friday seem like maybe the only folding bike company to realize this. that looks like a comfy ride you have! May I ask what your lowest gear is in gear inches?

jfouellette

Hi, yes comfort is important and usefulness in urban settings. Gear inches? That I dont know. Maybe someone can help here. The problem with this discontinued hub is finding a replacement indicator chain. Mine is fine but if ever it broke, I would need to change to a new dual drive. It needs to be longer because of the free hub added width. If buying the Archet S. Hub, I would also buy two extra indicator chains.

Ron Damon

It was a nice ride. It's the bike I regret selling.
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Yes, we know the SDD is discontinued. We discussed it here when SRAM announced it several years ago. From discussions here many many years ago (Bruce Metras was particularly knowledgeable) I seem to recall that the SA version was the precursor to the Sram DD, so it is very similar. That's why I brought up the SDD.

These hubs have a max torque limit so be careful. You need to find out the lowest safe gear ratio and on the basis of that calculate the max cog / chainring combo and GI. It's all simple arithmetic.
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FWIW, I paired the SDD3 with a 47x11-36T for 19-113GI. This was more range than I needed so I sold it because I could not personally justify the weight premium.

ChiapasFixed

19” would probably be good enough for me!
can’t find any specs on max gear ratio for the SA hub, hence why I asked here.
they aren’t all that expensive so maybe I’ll just go ahead and experiment. Likely end up with something very similar to what you’ve shown here, although I don’t think I’d ever use 113GI 😂

Ron Damon

I never did. That's why I sold it. It had excess range and I wasn't willing to pay for it with the excess weight of the hub. Around that time, wide range cogsets started to hit the market so I jumped on that bandwagon. Today, I would simply use a 1x drivetrain with a GS medium cage RD and a 11-46T or 11-50T cogset. Specially for touring where simplicity is a key consideration.


$25, 560 gram 11-50T cogset & $38 RD

ChiapasFixed

hard to argue with that, it may be the best solution - it’s just so big 😆

Duragrouch

Sachs bike components was sold to SRAM (who was only shifters at the time), who continued the internal gear hubs for some years and then (edited to correct) ended production (not sold to others).

I don't know of any drawback of a Rohloff except price, and weight, but the latter no worse than a dual-drive. I would particularly like the oil-bath lube that can be changed periodically and easily, versus takeapart for grease lube, and the Rohloff is supposed to have seals up to the job of keeping the oil in and rain out.

Sheldon Brown gear calc lists CS-RK3 for 8/9 speed, so you should be able to enter the cogs and tire size and know your gear inches perfect. About 20 is a good target low, I have 21-85 and use it all, might need a skosh lower if touring heavy with long steep sections, but not over 85, that's enough to pedal down mild grades. I have this 400% range via 50/34 x 11-30 on 20"/406 wheels, no internal gear hub.

Bike Fridays with Dual-Drive are available cheaper on the used market, not sure if because plentiful, or more expensive/fewer places to service the hub (not specific to DD, just all IGHs). There's one place in Seattle that does a ton of IGH service. But you will get plenty of gear range with an IGH+derailleur. Dahon had their Speed TR (Touring) with a Dual-Drive, too expensive at the time and didn't sell well. There's one for sale local now for $400.

If I need more range than 400%, I'll stay with 2X crank and go with a bigger cassette range.

CrimsonEclipse

You never show that bike with a 50t with the chain on it.

Why is that?

Leisesturm

I have a 2015ish Giant Expressway with a 53T x 11 - 32 and I hate the 33" low gear and top gear if IRC is around 93" which isn't all that useful. I spend all my time in the bottom gear or the one above. The o.p. is right, the SA hub is pretty reasonably priced for what it is, but unfortunately for me I got the urge to build mine during Covid and no one had these hubs. I found a wheelbuilder who was going to convert my existing rear wheel but he didn't have a source for the hub either. 18" is the low gear on my cargo bike and also the around town tandem I commute DW (blind) to work on every day. We use that 18" on every trip. I'm pretty sure the SA hub is up to handling the torque from the primary reduction. However, if my experience with my 33" low is any indication, a low of 22" to 24" might be just the ticket. A folder is not usually pulling a 100lb trailer up 8% grades.

tomtomtom123

The SRAM dual drive had a wider gear range than the sturmey archer.

I need at least 14-15 gear inches so 1X doesn't work for me. I have 2x with 24/44 chainrings which is 1.833 rear range and together with the cassette gives me around 515-520% gear range. The 20t jump is ok and shifts quickly most of the time but maybe 2 of 5 times I need to back off and try again to get the chain to catch on the pins.

This requires quite a bit of initial fiddling with the setup of the front derailleur because of the chain alignment with the thick seat tube. I use the SRAM force FD because the swivel mechanism makes trimming unnecessary for cross chaining.

Another option is the mountain drive from Schlumpf which is a 2.5 gear step down so when you stay in high gear you're in 1:1 mode with the better efficiency. Their speed drive is a 1.65 step up. It's expensive though. There's a licensed taiwanese factory that produces the speed drive for a cheaper price.

Duragrouch

Not quite that heavy, but my folder is typically 55 lbs + perhaps 20 groceries + fat me, and I do 10% hills all the time, some short 15%.

If the Expressway is 20"/406, you can get lower gearing, either by going mega-cassette 11-42 like Ron Damon and others, or 2X gearing as I note in the post above. Just shrinking your chainring will get you lower but not enough top end with just under 300% I think, I believe 400% is minimum in hill country, I'm not fast enough now to need over 85 gear inches.

Duragrouch

Just be sure to not buy the Joe Strumey Archer hub; The gears Clash.

CrimsonEclipse

A weird way to say you have garbage garbage ground clearance.
And you need giant tires to compensate.
Which slow you down and don't allow for any fenders.
But you won't switch back due to pride.

Nor will you post pics with the chain attached.

We're waiting.

TMonk

Ron Damon CrimsonEclipse please give it a rest. TIA.

CrimsonEclipse

He started it by being rude to everyone.
He posts after all of my updates.
He will be given no quarter until his attitude to everyone improves and backs off.

ChiapasFixed

really? I find Ron’s posts to be very informative and to the point, albeit somewhat short and imbued with an I’ve-had-it-with-knuckleheads attitude.

On the other hand I must ask you to not post any more attacks on my threads, or anything at all unless it’s useful information on the topic at hand.
thank you!

Ron Damon

Because it is a on-going, incomplete build. It's an open-ended work-in-progress where I try different things, one step forward, two steps back approach, taking different directions as the whim arises and interests change. As I've told you before, I have a few simultaneous builds going on but they tend to languish incomplete for several months, years even while I work on others, stop working on them altogether or change direction. It's not that I have installed the chain but avoided showing you what it looks like. I'll show the final, complete build in due time when it's done, on my time and for my own satisfaction.
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The real concern with that build, as anyone actually knowledgeable and experienced would grasp, is not RD ground clearance, but rather chain rub and RD lower pulley rub against the tire sidewall. A secondary concern is the shifting quality of the RD which is rated nominally for 42T max cog. Those, not RD ground clearance, are the issues. Keep your eye on the ball.

CrimsonEclipse

We'll see....

In the mean time, I'll keep my eye on the empty derailleur.

Ron Damon

Assuming a 50-406 tire/wheel, this is how I myself would play it: 42T x 11-36T, 10-speed with a stubby Shimano Zee M640 RD. Yeah, I know the spec sheet says 34T max cog and 9-speed, but I'd push it to 10-speed, 36T.


42T x 0.75 = 32T, 42T x 1.33 = 56T

Note the substantial gearing overlap.

FWIW, the gearing on the SDD3 is 0.73, 1.00 and 1.36, only marginally wider than the SA.

Duragrouch

That's an excellent range. And, like you said, large overlap, so that 2nd/middle-range means they can run 99% of the time in that range, and that's both more efficient (less friction loss, perhaps close to 10% savings versus low or high range), and saves wear on the IGH because 2nd/middle-range is direct drive. Good recommendation.

Ron Damon

The real-world useful range of that hypothetical setup is 18-86gi. The 102gi is aspirational and I would never use it. I've been there, done that: excess, useless range with a weight penalty. Ergo, I would simply try a 11-50T wide-range cogset to get about 18-86gi. KISS.