Rick Imby

Do many of you have one of the SRAM Automatix hubs on your folders?

What gearing are you using on 20" wheels?

How do you like it and how often do you ride it?

I am thinking about converting a single speed to 2 speed.

I am questioning as to whether I will like this thing shifting for me.

BruceMetras

I'm biased .. I've done a few 2 speed automatic conversions dating back to 2009 .. if set up correctly, they are a real treat to ride.. Links below are of my favorite conversions that I rode/ride regularly .. the Titanium road bike is the only one left in the stable .. the others went to happy homes .. they all had coaster brakes which I happen to like .. I never had a problem with the hubs through the years.. pretty much bulletproof in my applications.. the SRAM Automatix shares many of its internal parts with the Sachs Automatic from the 70's which was always a very reliable hub, even used in European tandems ..

https://www.bikeforums.net/13117387-post1.html

https://www.bikeforums.net/9824032-post1.html

https://www.bikeforums.net/15619970-post47.html

LittlePixel

I have one fitted to my 16" wheeled (iso 349) brompton and it's really nice.
A problem you may have is that a lot of these hubs are configured for larger rims, and as such the automatic shifting 'moment' is tuned for that larger size. This is done with a small internal spring that allows the hub to change when the centrifugal force reaches a certain level of force. Which means those hubs can change too early and you end up spinning. This spring can be adjusted if you're a particularly gung-ho mechanic who's okay with taking the whole hub apart and bending the spring, but it's definitely not for the feint-of heart. (I did this to mine to improve it and it's a lot better, but still shifts a smidge earlier than I'd find optimal and I'm not feeling the urge to pull it all apart again to re-adjust it).

I hope that doesn't seem like scare-mongering - if you get one that's intended for a 20" wheel everything should be fine and you can ignore the above, but I guess I'm saying make sure you're getting hold of a small-wheel version — or it may not do all you hope it will.

If you can only source the big-wheel one and fancy the job of taking it apart to adjust the shift-timing then there's a good guide here:
SRAM Automatix two speed: Review and Adjustment

Rick Imby

I read a bad review a while back and I did not know if that was the general consensus. It looks like a fun addition to a single speed.
@BruceMetras great picture of your Mu Uno converted. I would have had a tough time selling it.

Rick Imby

How much resistance is there with the coaster brake, does it drag a lot like most of them?

keyven

I had the SRAM Automatix installed on my Dahon MU Uno a few years ago which I heard shifts between gears at "too low speeds" at default. Which is quite true because at around 8mph it would switch, and jump in resistance is quite jarring.

I never did but it can be tweaked. I sold the bike a few months later.

BruceMetras

My experience is that I never noticed either the Sachs or the SRAM dragging .. 15 mile loop tests over years showed them to be very efficient compared to my derailleur equipped bikes .. with my Titanium road frame, if I thought the coaster brake was draggy, I could have ditched the hub for an Automatix without coast brake and installed a caliper brake easily enough, but never gave it a thought ..

pinholecam

I have this on a Java X2.
Stock 'auto' setup isn't that great and it shifts way too early (I have what is supposed to be the small wheeled version of the hub)

I've not plucked up the courage and effort to get it modified though.
My daughter uses it so its fine for kids, but way too early for adults.

jur

I put one n my spare Swift, commuted with it for quite some time, put many miles on it. Like others, I also found mine to be the cause of knee death, and set about modding it. I opened it around 5 times to get it perfect. It shifts at 27km/h.

The upshift is seamless, while the downshift requires you to ease off the pedals momentarily. That is a very good thing as you don't want the resistance to suddenly drop as you are standing on the pedals cranking up some hill.

The only times I found the upshift slightly unwelcome was when I was sprinting away from the lights and would have liked it to stay in low gear slightly longer.

I have the backpedal brake version. I didn't think it to be draggy, and I am obsessive about stuff like that.

ThorUSA

I think the consensus is that a lot of riders, who ride very frequently and are in good physical shape prefer the hub to shift later than it does.
Than its peeps like me ( old and out of shape ) who ride more in frequently and they like the shiftpoint around 9 miles per hour. I can start with ease, ride up hills in first gear, and it shifts before even I run out of steam ...


I had no trouble with the coaster brake or freewheel version on any of my bikes. And from the feedback of my customers they had no trouble either.
Although no Dahons or Terns are available standard with the hub, I keep building Tern Unos with the rear wheel I am selling in either version. The Tern model verge Duo was a 1000 dlr when it was available, my custom builds are way more affordable .