SRAM Automatix

[Modbikemax]

I fitted the SRAM Automatix hub to one of my bikes yesterday.
It is a 2 speed automatic gear changing hub. The low speed is 1:1 and the high is 1:1.37.
The change comes automatically at 16kph. This, unfortunately, is about 2 pedals when taking off in ernest.
Below 16kph is pretty slow so apart from sight seeing is too slow to be really useful for commuting.
However there is a mod to adjust the changeover to a higher speed. I will give it a go.

Anyone else had experience with these?

 

[emmetbrown]

So I guess you got the version for 36 spokes.
The one for 28 spokes changes to second gear at around 20 kph.
Laced into 26" wheels.

 

[Modbikemax]

So I guess you got the version for 36 spokes.
The one for 28 spokes changes to second gear at around 20 kph.
Laced into 26" wheels.

Thanks for that info. I did not know they were different.

I have bent the spring and it now changes at 20kph. Not difficult to do but I did lose the spring for a couple of hours after it shot out of my fingers .

 

[Chalo]

I fitted the SRAM Automatix hub to one of my bikes yesterday.
It is a 2 speed automatic gear changing hub. The low speed is 1:1 and the high is 1:1.37.
The change comes automatically at 16kph. This, unfortunately, is about 2 pedals when taking off in ernest.
Below 16kph is pretty slow so apart from sight seeing is too slow to be really useful for commuting.
However there is a mod to adjust the changeover to a higher speed. I will give it a go.

Anyone else had experience with these?

I built one for myself. For whatever reason, mine shifts at about 15mph (24kph) with a 700c wheel. That works OK for me, because it corresponds to about the fastest speed I can comfortably pedal in the low gear, and a nice relaxed cruising cadence in the high gear. Based on the research I did, I expected something very different, but the shift point I got is something I can live with.

 

[Modbikemax]

with some spring bending i have managed 26kph shift which is much better.
It some times shifts early if I hit a bump, I suspect the little spring is struggling to hold the weights.
I want to try some weight reduction on the weights with a grinder. Could be good or could turn to shit, I will let you know how it goes.

 

[emmetbrown]

I guess spare parts should be available easy, as normal for Sachs/SRAM hubs.
So just go on, its interesting, perhaps you could do a list with weight<--->shift points

 

[cjh]

Just wondering how you're finding it? Thinking about it for the wife's bike with a front hub motor as she hates changing gears. She just goes for leisurely rides. It seems that the sprocket installed on the hub can have 15,16,17,18, 19, 20 or 21 teeth so there is a bit of room for tuning the gearing.

 

[fevitz]

Ive had this for approx 2 and a half yrs . I don't know its ratios , but I use it nearly every day for work commuting (fantastic) the ratios may not work for everyone but I find it suitable to my requirements . Ive heard of a 3 speed automatix with a 5 sprocket cluster has just come out ,,,,,,,,,has anyone heard anything about this ?
I made up a brake clamp from a 1/8" or 5mm piece of aluminium to lock the lever arm as the flimsy clamp that came with it spat the dummy just after 2 days of braking . ive used a small piece of tube around the inside to stop any paint scratches from bolting it on .

 

[gogo]

Ive heard of a 3 speed automatix with a 5 sprocket cluster has just come out ,,,,,,,,,has anyone heard anything about this ?

That sounds like it could result in some 'busy-ness' when shifting the cluster.

 

[fevitz]

Ive heard of a 3 speed automatix with a 5 sprocket cluster has just come out ,,,,,,,,,has anyone heard anything about this ?

That sounds like it could result in some 'busy-ness' when shifting the cluster.

That's what I thought but it could make for an interesting ride though ,,,,,,,!

 

[Modbikemax]

Just wondering how you're finding it? Thinking about it for the wife's bike with a front hub motor as she hates changing gears. She just goes for leisurely rides. It seems that the sprocket installed on the hub can have 15,16,17,18, 19, 20 or 21 teeth so there is a bit of room for tuning the gearing.

It's just bearly ok. The change is pretty big so you are either spinning or grinding. After playing with the spring tension I have got it to change around 26 kph but the change up is still like hitting a brick wall. A closer ratio would be better. It is no wonder we don't see more of these as standard offering on stock bikes. A 3 speed hub gear with a manual selector is a much better option. Select a comfortable ratio for the Middle gear which you use the most.

 

[cjh]

Ive heard of a 3 speed automatix with a 5 sprocket cluster has just come out ,,,,,,,,,has anyone heard anything about this ?

I know SRAM showed off a 3-speed kickback hub with a coaster brake last year but where did you hear about a 3-speed Automatix? That would be much better.

 

[nz_aj]

I‘ve been commuting with this hub for about 9 months and covered about 3000km.
I‘m 188cm and a bit over100kg with a backpack on. About half my commute is hilly, the flat section typically has head and tail winds.
Its built into a 700c x 25 wheel running 43 tooth chainring and 19 tooth cog, giving about 60 gear inches in low and 82 in high. This is only just low enough to prevent stalling on the steepest hill, and when in top it still gives a comfortable cadence when keeping up with 95% of road bikes.
I‘ve removed the sram sticker so everybody thinks its singlespeed.
I‘ve adjusted the spring so that a comfortable cadence can be maintained in low with it only changing when cadence is quite fast, resulting in a comfortable cadence in top once changed rather than hitting a brick wall.
I find these ratios to be perfect just about all the time. If it had a third ratio, maybe I‘d make low slightly lower, keep high the same, and have another gear in the middle.
It does change up when riding over bumps in low at a cadence near the shift point, and won‘t change down while there is load on the pedals. Easing off lets it change down, or I might stand and accelerate depending on whats ahead. I don‘t find this to be a big problem.
Originally when I built the wheel I didn‘t use spoke washers. I broke a spoke after a couple of weeks. With the addition of washers the spokes are now pulled up hard against the hub flanges. No more have broken, although I‘m not using the hub brake much and never hard anymore.
I really like this hub, and so do my knees, probably as I‘m out of the saddle for all the steeper hills, and spinning fast on the flat with not much load. Its nice not to have to think about changing gear, just stand or sit. I‘ll continue to use it in preference to my multispeed bike. Theres also much less maintainance, 8 speed chain lasts me at least 4 times longer than 9 speed, and there are no cables that stretch/break or derailurers that need adjustment.