pacificcyclist

Hi everyone,

Got a Speed UNO recently and now want to mod it to have dual speed. What are your experiences, thoughts and suggestions with adding a dual speed coaster hub? And what's your setup and why you like it done that way.

I'm currently torn between the Sturmey-Archer B2C kickback and the SRAM A2 Automatix. I know that the SRAM A2 is 130mm, but I heard somewhere that it is actually 120mm with 2 5mm spacers?

Thanks again for your kind thoughts and suggestions!

Dynocoaster 

I have the S2C on a Raleigh folder, come down and try it out. I have the new Sram 2 speed automatic and have not had it built up yet. I just order the Speed Uno from Thor.

Dynocoaster 

I like the S2C and got it with the coaster brake which gives the bike a clean look without any cables. The sram is without coaster as it is going on the nano. There is a thread on this and hank has a Speed Duo and it looks good.

pacificcyclist

Maybe I will take your offer if I head down to the states again. Speaking of which, what gear inches you had set up on your Raleigh? And how difficult is it to shift gears?

Will the SRAM 2 speed fit on the Speed UNO?

Thank you for sharing your experience with me.

SesameCrunch

I have had my S2C for almost a year now. Started out great, but it's giving me problems lately. 3 times, the hub has bound up for no reason. The wheel just would not turn no matter what I did. Then, the problem goes away just as suddenly.

Apparently, others have experienced the same thing.

frank13

The SRAM A2 is awesome. Just put one on my Mu Uno and love the way it shifts but only have it a week, and cant compare it to other two speeds. To me the coaster brake on A2 feels better feel than stock Mu Uno hub.

I had my SRAM A2 wheel built by Universal Cycles with a Sun Rynolyte rim shipped to my door (in California) for $174, including additional 18 tooth sprocket. (the SRAM hub comes with a 19 tooth sprocket) The guy I spoke with on the phone at Universal was great, and took much time to make sure I got the right stuff. Got the wheel as promised in a week. Bolting it on the bike was super easy, I only had to drill a new hole on the hubs brake arm to bolt it onto the Mu Uno mounting spot.

I expected to new rim hub combo to be noticeably heavier than stock one (didn't have a scale handy) but couldn't tell the difference in weight holding both side by side.

pacificcyclist

Hmm, this is a very interesting revelation. Is there a thread here with someone discussing this?

pacificcyclist

Did you tell the guy at Universal to change the shift point before they ship it to you? I found the Speed Uno's coaster brake too grabby, so it's good news to hear that this hub improves braking! I'm also leaning heavily towards the SRAM A2, but am a bit concerned how to auto-shifting works shift point wise. Any more thoughts on this would be greatly appreciated!

SesameCrunch

Pacificcyclist:

You need to consult Bruce Metras about both your questions. He is aware of the S2C issues. He can also change the shift point for you (he may be the only one who knows how to do that at this stage.)

frank13

No, and they probably wouldn't know how to adjust the shift anyway. Shifts early, around 5-7mph but ridable, and much better than just one speed. Figured I would take it apart and see if I can find or make a stiffer spring as Bruce advises. Think a shift around 10-12mph would be perfect for me. But not in hurry as recently had knee surgery and supposed to stay off bikes for couple months.

Wonder if Bruce would be willing to sell us some of his custom wound springs?

Transformer

I'd like to hear more about problems with the S2C as I'm seriously considering buying a Moulton TSR 2.

Dynocoaster 

https://www.bikeforums.net/showthread...?highlight=s2c

https://www.bikeforums.net/showthread...?highlight=s2c

pacificcyclist

Hmm, yeah it would be nice indeed to have those custom wound springs..

Btw, when the hub shifts, does it shift seamlessly and noiseless? Sounds like the SRAM A2 is the most popular choice.

pacificcyclist

SesameCrunch; thank you for the pointers.

frank13

Yes very seamless shifting. Much better and quicker than on a derailleur bike. Just pedal a few turns up to around 6-7mph then "click" pedaling gets a little harder because it shifted into high gear. Slow down to under 6mph, or stop, and it just shifts itself back into first. You hear a faint rhythmic clicking in high gear, but not bothersome to me. But it does shift too soon on a 20inch wheel as I wouldn't want to have to climb hills at under 6mph to stay in first. But I plan on modifying shift point after my knee gets stronger, being I just had ACL surgery 3 weeks ago. Right now I'm only supposed to be riding stationary exercise bikes till Nov, but couldn't resist riding the new rim around the block a couple times. So that is the extent of my experience with it.

tcs

The Automatix only hit the aftermarket in the last month and no one can claim to know if the hubs are robust or durable yet. SRAM has released no tech information (tear down, exploded diagram, part numbers, etc.) on this hub yet beyond their repeated - and erroneous - claim the hub features a 124% range. The Automatix is built in SRAM's new factory in Dali, Taiwan (not in old Fichtel&Sachs center in Schweinfurt, Germany). Sadly, today's SRAM North America doesn't seem to know it is in the internal hub gear business (see Parts Availability), which is a darn shame. Changing the springs or weights in an Automatix to adjust the shift point will void the warranty.

None of this makes me any happier than the trouble folks have experienced with the Sturmey S2.

BruceMetras

Thanks for the interest.. right now, it's sort of cost prohibitive to sell any springs because it takes way too long to fabricate and sell reasonably.. I'm working on different solutions.. the other thing, there is a bit of hit and miss when it comes to dialing it in and has required a bit of road testing to get the results I'm after .. I know I'm in the ball park, but not ready to sell springs blindly without my running the wheels here and then making any needed adjustments.

SesameCrunch

My sentiments exactly!

pacificcyclist

Thank you Frank13 for sharing your riding experience with me. I also like to know how to modify the shift point also; perhaps somewhere around 10 mph or so would be a good start at least for me. I hope your knee get stronger so you can ride your Duo more and post more of your faboulous experiences here with all of us!

pacificcyclist

Wow Bruce, I am definitely looking forward to your solutions!

By the way, maybe you can answer for me. Will the SRAM i-Motion 3 coaster hub fit on my Dahon Speed UNO eventhough it is advertised as being 130mm?

Thanks!

pacificcyclist

I looked at their website and they sell the hubs in one of the 4 preset shift points. So I am wondering if one can order a hub that is set to a specific shift point in the factory. That way you don't have to mess with the weights and springs? No?

Thanks!

BruceMetras

I wrote about that HERE .. but it might be worthwhile to read parts of the entire thread to get a better understanding of what is being sold in the US..

BruceMetras

True, the A2 is unproven, but it is based on a highly proven Sachs Automatic that was both robust and durable.. much of the same technology is used... modifying Sachs auto shift points is nothing new to me and many others before me ..

I highly doubt that shift spring changes will affect the hub's warrantability .. or that a product rep would even recognize a change had been made .. or even care on a sub $40 wholesale hub ... making changes to the shift point springs is exactly how it has been done in the past.... possible warranty claim failures like bearing failure. brake failure, hub flange failure, axle failure or the like wouldn't be affected by shift springs.. once you have either of these hubs apart on the bench, it becomes much more apparent..

frank13

I can understand after looking at the hub diagrams, must take a bit of time to custom make that little spring and get the shift point just right. I'm curious. Can you give us an top of the head, squeezing with your fingers estimate how much stiffer your hand made spring is? Would you say its twice as strong as stock one, or much less like a third or quarter?



I google searched and found great pictures of the older hub the new SRAM is based on, completely taken apart:

https://www.hubstripping.com/f&s-auto.../DSCF2589.html

You can see the shift spring and weights good at the bottom of this page:

https://www.scheunenfun.de/f+s_automatic.htm

As Bruce says, making a stiffer version of that little spring by hand, and getting it to shift at the right point must take some skill a bit of trial and error. As it would be difficult to measure the tension of that hand made spring and duplicate it each time.

Looking at the setup, if I cant easily find the right size in a slightly stiffer spring, think I might try grinding down a tiny portion of the shift weights. As once I get the right amount ground off, take a picture of it, it would be easier for anyone to reproduce if it works out well. I figure worst case, if I go too far grinding on the first round, I can bend (weaken) the stock spring a little bit to make it shift a little sooner. If I screw the hub up completely... well hey, they're pretty cheap, and start over.

Wish we could buy parts. Bruce stiffer spring, or even a stock spring to add to the other side and see how that would do. In any case, thanks to my knee surgery, I probably wont be messing with it for a few weeks. But will share pics of what I do, when I do.

But even stock shifting early, for me, its much better than having just one gear. I wonder if Tern is using a different version of the SRAM on their Duo. Or if they modify it, or let it shift early. Maybe someone who has ridden the Tern Duo can answer, by telling us approximately the mph of the shift.

tcs

Interestingly enough, the Sturmey S2C is based on the old Sachs Duomatic.

From the SRAM warranty: "This warranty does not apply when the product has been modified." That's pretty clear.

So the plan is to violate the stated terms of a product's warranty, and then, in the case of trouble, hope the manufacturer won't notice?