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jerrysimon 07-18-12 10:51 AM

SRAM Automatix (A2) on a Brompton :)
A few of us here have been trying out these hubs with the recent re-emergence of the old two speed auto and kick back hubs both with and without coaster brakes. Both SRAM and Sturmey Archer have now come to the market with new versions.

I initially came across the S/A, S2C kick back coaster brake version which I tried and hated. The change is inconsistent and there have been cases of it locking up. S/A's customer service is also appalling when you email them about this hub. They even removed the face book page which contained lots of complaints.

I have have recently fitted the new SRAM Automatix to my belt driven Moulton TSR2 and its a dream to use. That too has the S/A S2C fitted as standard.

I have toyed with the idea of fitting one to my Brompton for a while, but there are a few issues that initially put me off. The main being it was initially only available with 36h flanges which meant using different non stock Brompton rims or Brompton blank rims drilled with 36h which no longer seem to be available. Sun CR18s would suffice but I am not a fan of the 16" version with their shallow well making getting tires on and off difficult. The auto gear change point would also be quite low as the first A2s to appear were speced for 26"+ rims. Another problem is that the hub comes with an OLN of 120mm and spacers for up to 130mm. As we know the Brompton rear frame spacing is around 112mm :(

Anyway I noticed that 28h versions are becoming available in Germany initially without the coaster brake and specified for smaller wheel rims 20"-24" so the auto gear change point would be more appropriate.

Well my A2 turned up from Germany (good value at the moment with the weak Euro) and using some 148mm spokes I laced it up. The thin flanges require you use washers to get a good fit.

The next problem was the wider OLN. I spoke to some of the engineers at work and one reckoned the hub would be fine using only one of the two locking nuts as long as I "set" it when I tighten up the wheel nuts. He also took a mm or so off the single nut in the lathe bringing the OLN down to a healthy 115mm which meant it then just queezed into the rear 112-113mm Brompton spacing snugly.

The hub is specified for a 16T sprocket minimum which just fits in the frame without fouling the end of the chain stay. I guess you could use smaller sprockets but when I tried one you can't then get the dust cover on and the chain line is all wrong.

SRAM hubs tend to have their cog spacing/chain line slightly different to S/A. I wish these guys would standardise, though at least the sprockets are interchangeable. Using a smaller flat sprocket and different chain line (its about 2-3mm out) would also cause problems with the chain tension jockey wheels which would require washers to space them.

Because of the larger sprocket I swapped out my 50T main (which I was using for my S/A three speed hub) for a 54T which gives me a nice range of 56" and 76", better than than the stock Brompton two speed 56" and 74"

Here are some pics

The hub axle is a little long on the non drive side but can easily be cut/shortened.

I have been out for a ride and it changes up/down about 8-8.5 mph. I marked the locking nut and it is fine not moving once I set it to get the right pressure on the bearings (basically hand tight). The wheel nuts then clamp it up tight in the frame so nothing moves.

I live and cycle around Cambridge and it seems perfect for that, plus my Bromptons have added electric assist. Getting rid of a cable is nice and not even having to think about changing gear is good as well.

Weight wise there is hardly anything in it. The SRAM A2 is about 100g heavier than the S/A three speed, but by the time you remove cables, fittings and changer/trigger it balances out.

I will report back later if I get any problems. It might be worth trying the 28H SRAM A2 WITH coaster brake when it comes out later this summer, but again the tensioner can then be problematic.



tcs 07-20-12 09:08 AM


Originally Posted by jerrysimon (Post 14497588)
S/A's customer service is also appalling when you email them about this hub. They even removed the face book page which contained lots of complaints.

Nope. Facebook eliminated the "forum" feature.

jerrysimon 07-20-12 12:23 PM


Originally Posted by tcs (Post 14506573)
Nope. Facebook eliminated the "forum" feature.

Oh I heard a rumour of that. My oppologies.

That said I emailed them several times about problems with the hub initially receiving no replies and when I finally pressed them for one, they were rude and offhand. This was not a one off I tried two of the hubs.

No problem though it worked out well, I took my business to SRAM and as stated much prefer and am glad I found the A2.



fietsbob 07-20-12 12:51 PM

I replaced the spokes ,a couple broke , on my AW3, Brompton spokes are 12 gage
thickies , for durability.. I didnt need brass washers..
but it looks like it went together .. Extra leftside axle is useful .
a trailer hitch , perhaps ?

so you are actually not pedaling, so much as getting the Pedal-electric motor doing the work,

then the Trailer to haul stuff is definitely practical..

jerrysimon 07-21-12 02:12 AM

I always pedal as I use one of the smallest/lightest low powered motor hubs available. Obviously you are right though the e-assistance is helping me by taking some load (maybe 60% max) and I can then dial in as much or less power as I need. From this perspective the A2 hub on the rear is a perfect match.

If I had no assisted power then I think I would favour another couple of mph before changing say around 10-11 mph. I may take the hub apart and fiddle with the spring. Any pointers on how to do this would be helpful.

Although I can see an application I am not really interested in a trailer. I tend to use my Brompton/small wheeled bikes for small messages and even have the big Brompton open bag for local shopping/grocery trips. If I need to do a large food shop I order on line or take the car lol



fietsbob 07-21-12 09:50 AM

Horses for courses, I guess .. my Carry freedom city trailer is a good match .
Mine currently not used often, though.. ( wish the bag was more watertight,
for 1, the Zipper choice could have been better)

Importing seller in the states stopped selling them, so now buyers have to go to UK sellers

lectricas 12-10-12 03:34 PM

Hello. Today I bought
and its cheaper than
SRAM 36h Automatix 2 Speed Coaster Brake Rear Hub
is that means that SRAM 36h Automatix 2 Speed Rear Hub has no coaster brake or it has it, but just dont have a brake arm?

jerrysimon 12-11-12 04:14 AM

Not sure I really understand the question :(

The SRAM 36H Automatix comes in two versions, with or without a coaster brake. The 28h version initially just came without a coaster brake but has been available more recently, in limited supply, with a coaster brake. I think more are due this month. The advantage for me of the 28H version is that I could use a standard Brompton rim to lace it into. Although Sun produce double walled 16" rims I find fitting tires to those a pain due to the very shallow rim well.

PS I have been using this setup for over four months, commuting every day (10 mile round trip) and this hub is wonderful. I would add that my commute in Cambridge is pretty flat and I have a light e-assistance set up :p



bargainguy 12-15-12 11:24 AM

One advantage of this hub (coaster brake version) is no need for any brake or shift cables. Haven't seen one yet but I would imagine it's a very clean look.


jerrysimon 12-15-12 11:40 AM

Agreed plus no need to change brake blocks and no wear on the rim.

Unfortuantely the coaster brake version is still not available for the 28h version only the 36h one.


questionesse 08-02-14 01:59 AM

Hey there,

how's the experience so far with this hub?
Any other long-term testers?

The weight without coaster brake is supposed to be below 800g
-> plus saving on all other parts the Brommi 2gear would need, cables, shifter etc.

Anyone ever did the maths what's the potential weight saving?

btw. what's the weight of the brompton hub for the 2gear?

questionesse 08-04-14 09:43 AM


chagzuki 08-04-14 10:02 AM

Nope, but I'd guess the weights would be very close since the 2 speed hub is a lot lighter.

Rear brake, probably 140g
brake lever around 75g
Gear shifter... 50g? Less maybe.
cable...I forget, 80g x 2, or something like that.

questionesse 08-11-14 10:21 AM

What's the weight of the 2speed hub anyways?

dynaryder 08-11-14 04:46 PM

720-1420gr,depending on brake setup.

tds101 08-11-14 05:20 PM

Post some pictures already,... I want to see these babies!

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