SRAM A2 Automatix; introduction to the internals

[scooby214]

it certainly is not too complicated inside.

BTW it isn't a bad idea to remove the RH cone and put a load of grease in there for the planet gears themselves; I'm not sure it will migrate into this part of the hub easily otherwise.

cheers

What grease would you recommend for the planet gears? The stuff that came in there looks to be #00 grease. It's not quite runny like 90wt gear oil, but not as stiff as wheel bearing grease.

[Brucey]

pretty much any grease is better than none for the gears; however for the pawls and the bob-weights a thicker grease might be too viscous in cold weather. If it isn't too cold where you are a #0 or #1 grease might be OK through the whole hub.

Since the gears are quite well separated from the rest of the hub you could even use a #2 grease in there I would expect

cheers

[scooby214]

pretty much any grease is better than none for the gears; however for the pawls and the bob-weights a thicker grease might be too viscous in cold weather. If it isn't too cold where you are a #0 or #1 grease might be OK through the whole hub.

Since the gears are quite well separated from the rest of the hub you could even use a #2 grease in there I would expect

cheers

I plan to stick with light oil for the weights and pawls. I tried out some #2 grease this morning, and didn't like the result. The hub felt noticeably less efficient in high gear. It took more work to spin my usual cadence on a known stretch.

Since I had the day off, I decided to do some experimenting. I took the hub completely apart, degreased the gears and the planet ring. When it was dry I put in some Phil Wood Tenacious Oil. I went for a 20 mile test ride, and it felt as efficient in high gear as it did before I added the #2 grease. I then took the hub apart, and found the Phil Wood oil had oozed out and made a bit of a mess. I degreased everything again and allowed it to dry.

I then picked up some #00 grease from my local Snapper lawn mower dealer ($4.00 for 9 ounces). I reassembled the hub once again, using the Snapper grease. I thought the gear assembly was inadequately greased from the factory, so I put in a bit more than what it originally had. I didn't fill it completely, as I didn't want it to ooze out at the edge of the planet ring and end up on the weights and pawls like the Phil Wood oil. The #00 grease reminds me of jelly, in that it doesn't run, but it is nearly runny.

This time, I also degreased the bearings and packed them with marine grease. I swapped out the o-ring for one that was slightly thicker. This completely cured the rattle that plagued the hub since I got it in June. I'm pretty confident that the original grease SRAM used in the gear assembly was #00 or something similar. I took another test ride, and the hub felt great. It felt noticeably easier to spin the high gear than with the #2 grease.

The A2 is such an easy hub to work on that I'll probably take it apart again soon and see how my grease job holds up. I had a lot of fun playing around with it today.

[Brucey]

all very interesting; glad you have fixed the rattle.

Seems like you are having fun there too!

BTW I wondered about adding a lube port to the hub shell, but I was concerned that the grease wouldn't necessarily get to the planet gears themselves.

cheers

[ratherbeintobago]

Quick question - is the Automatix sprocket a standard fitting, and if so, what?

Also, are there three different springs for controlling the shift point as implied by the SRAM website, or is it just a case of tweaking the one that's there as per the blog instructions?

Thanks,

Andy

[Brucey]

the sprocket fitting is the same one as used by sturmey archer, shimano, favorit and others on hub gears and coaster brakes etc. It is the most common such fitting.

The hub is supplied with a spring in it; if there are others made, it isn't clear that they are available in the UK. Maybe contacting SRAM europe would be useful; they have been helpful to me in the past.

You can of course fiddle with the existing one; I reckon you could make a substitute spring easy enough too.

cheers

[ratherbeintobago]

the sprocket fitting is the same one as used by sturmey archer, shimano, favorit and others on hub gears and coaster brakes etc. It is the most common such fitting.

The hub is supplied with a spring in it; if there are others made, it isn't clear that they are available in the UK. Maybe contacting SRAM europe would be useful; they have been helpful to me in the past.

You can of course fiddle with the existing one; I reckon you could make a substitute spring easy enough too.

cheers

Thanks for that - question about different springs came from the following from the SRAM product page:

The shifting points can be preset by SRAM according to the guidelines of the bicycle manufacturer at certain speed limits which can be 12, 14 or 18 km/h (7.5, 8.7 or 11.2 mph).

If I get as far as acquiring a commuting bike, I'll drop SRAM a line - the suggested shifting point of 10mph seems a bit low to me.

Andy

[Brucey]

note that the shift point for any given spring is not absolute, but depends on wheel size. The hub 'doesn't know' how fast the bike is going, only how fast the hub is turning.

cheers

[ratherbeintobago]

The hub 'doesn't know' how fast the bike is going, only how fast the hub is turning.

Yes - I did think that SRAM had put it a slightly odd way.

Andy

[E27006]

Decathlon sell a city bike with the Automatix hub in a 24 inch wheel, Price is £169, Styling is step through, a variation of a "Boris bike"

It might be a way of acquiring the hub, Decathlon have clearance sales from time to time, I'm keeping an eye open for such a clearance event.

[E27006]

As an alternative to tweaking the spring on the bobweights, is it feasible to modify the bobweight by grinding off some of the metal? .

[Brucey]

don't see why not, but the adjustment would be one way and permanent.

cheers

[Velo]

A very informative and helpful thread. Two question though, what is the chainline on the A2 hub and does anyone have any experience of the roller brake version?

[Brucey]

roller brake? You mean coaster brake? My comments refer to this version unless otherwise specified.

Re chainline; The coaster brake version comes with a minium OLN of ~120mm and the chainline is 45mm. This is ~ +/- 2 or 3mm since sprockets are reversible/dished and there are spacers on the mounting as well.

The axle is quite long, (~178mm or so) and even if you need 20mm each side for thick dropouts and good track nut engagement, it still means that you have 18mm to play with. Thus if building the hub up +10mm OLN (i.e. 130mm OLN) you can put the spacers either side and adjust the chainline another +/- 5mm.

This allows considerable freedom in chainline.

cheers

[skankingbiker]

Newbie here. Joined this forum because this is the only place I could find where this hub is discussed. I am trying to find the build dimensions for the hub. None of the SRAM literature has the necessary information to calculate spoke length.

Does anyone have the build dimensions handy or know where I can obtain them?

Much thanks.