SRAM A2 Automatix; introduction to the internals

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kunakuna
Posts: 2
Joined: 26 May 2017, 5:25pm

Re: SRAM A2 Automatix; introduction to the internals

Postby kunakuna » 26 May 2017, 5:38pm

Brucey, thanks for your detailed posts on this thread - really interesting. I've just built a bike with an A2 coaster hub, have opened it up to pack more grease in and adjusted the spring tension and am really enjoying the ride. Couple of questions:

- I'm noticing that the hub can prematurely upshift when the rear wheel hits a bump. I've only noticed this since reassembly but didn't ride it more than 5 miles before taking it apart anyway. Is anyone experiencing this too? Presumably this happens when the wheel bumps downwards whilst the sprung bobweight is beneath the axle.

- I'd like to have a go at attempting to fit an oiling port on the hub as I have successfully done this with an old nexus 7. Of course the brake side needs to contain grease and I imagine that grease is preferable on the drive side to prevent water ingress. So an oiling port would lead to a mixing of lubricants at either end of the internal unit. Is this potentially problematic? Brucey, is this why you are thinking of using a liquid grease? Thoughts on this would be appreciated. Also cheers for the tip on the shell possibly being hardened; hadn't thought of that.

FYI these hubs are available from Zyro which many UK bicycle shops have a b2b account with (this is how I got mine).

Cheers

kunakuna
Posts: 2
Joined: 26 May 2017, 5:25pm

Re: SRAM A2 Automatix; introduction to the internals

Postby kunakuna » 26 May 2017, 6:52pm

Thanks Bruce for the detailed comments. I've just built a bike with the A2 coaster hub, greased it and modified the spring tension and am very happy. Question:

- The hub can upshift prematurely if going over bumpy road surface. Has anyone else noticed this? I've only noticed it since reassembling the hub but then I only rode it for a couple of miles beforehand anyway. Presumably the shift occurs when a bump is hit and the sprung bobweight is positioned beneath the axle, so it gets swung out by the jolt of the wheel.

Also, thought about fitting an oiling port but the hub shell is indeed hardened. I tested this with a file on the middle of the shell and could only get superficial damage before the file just glides over. No, I don't mind damaging the hub aesthetics...

Saw a few posts saying these hubs are difficult to get hold of. Zyro can supply them and plenty of UK shops have accounts so I'm not sure what the problem is there.

Brucey
Posts: 35195
Joined: 4 Jan 2012, 6:25pm

Re: SRAM A2 Automatix; introduction to the internals

Postby Brucey » 26 May 2017, 8:07pm

yes the hub can upshift prematurely over bumps. IMHO this occurs because there is a small amount of lash in the bobweight assy; if there were none, bumpy roads wouldn't affect the shift point because the inertial loads on the two bobweights would balance, i.e. cancel one another exactly.

Zyro may well be able to supply this hub for now but this won't last; SRAM recently announced that they are ceasing manufacture of all IGHs and furthermore that they will also stop manufacturing spare parts. Once the current stock of spares dries up, that'll be it.

FWIW I think this will be of particular importance to 5s and 7s hub users; these systems use crappy clickboxes, pushrods and those ridiculous little red plastic guide pieces. These bits find new and exciting ways of knackering themselves on a daily basis. By contrast most of the oily bits inside the hubs are OK. I was working on parts that will replace the crappy clickboxes etc anyway, but I'm even keener to get this done now that there won't be an alternative before too much longer.....

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~

ratherbeintobago
Posts: 323
Joined: 5 Dec 2010, 6:31pm

Re: SRAM A2 Automatix; introduction to the internals

Postby ratherbeintobago » 28 May 2017, 8:42pm

SRAM recently announced that they are ceasing manufacture of all IGHs


Did they say why?

Col18
Posts: 21
Joined: 13 Jun 2018, 3:23pm

Re: SRAM A2 Automatix; introduction to the internals

Postby Col18 » 13 Jun 2018, 4:49pm

Hope someone will be able to help, I know the this thread is old and long.
I have the SRAM Automatix and I finally took the step to take apart and adjust the spring.
I cleaned up a bit and added more grease around the the bearings.
Put the hub back together and the cranks arm spins back freely.
But when I go for a ride and come back the crank does not spin freely backwards.
When I spin the rear wheel backwards, it turns the crank arms as well.
It free wheels fine.
I've looked at this 3 times now. Adjusting the cones/cover, the two 22mm nut so it is not too tight, not too loose.
Every time I cycle it has turned the axle of the hub slightly.
If I tighten the two end nuts, it can then clamp/squeeze onto the cone/cover and the crank again does not spin backwards freely.
When I cycle low feels fine, higher gear feel a bit harder to pedal than before.
When I've had the hub out, hold the axle and spin the sprocket, it spins smoothly and you can see the weights pushing outwards.
On a good note, the gear change is 13/14 mph which suits me.
Hope some can help and advise. Thanks.

Brucey
Posts: 35195
Joined: 4 Jan 2012, 6:25pm

Re: SRAM A2 Automatix; introduction to the internals

Postby Brucey » 13 Jun 2018, 6:32pm

You need to set the hub up so that the track nuts can be fully tightened in the usual way. [ If the axle spins in service this can throw the bearing adjustment out and this will ruin the hub. ] In some cases it is best to fit NTWs (the hub comes without them, but they can be added).

If tightening the track nuts fully alters the bearing adjustment then something is wrong with the way the hub is set up. IIRC the RHS cone is screwed against a shoulder on the axle; this needs to be tightened first before you screw the LHS cone on/adjust it. To do this, back the LHS off, mount the axle RHS in a bench vice, and tighten the cone fully.[ It won't hurt to use threadlock on it, in fact.] The adjust the LHS, being sure to lock the adjustment properly.

I suspect you are within a hair's breadth of being set up nicely; a little tweaking and you will be there I think.

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~

Col18
Posts: 21
Joined: 13 Jun 2018, 3:23pm

Re: SRAM A2 Automatix; introduction to the internals

Postby Col18 » 14 Jun 2018, 10:21am

Thank you for your help and advice.
The bike has Non Turn Washers with the serrated face to lock/clamp onto the chain stay.

How does the hub get ruined if the bearings/bearing adjustment is not aligned?

The first and second re-fitting, the axle had twisted after a cycle, I don’t think it was spinning when I was pedalling. It needed a lot of force to unscrew the end dome nuts. I assume a larger force (going up hill?) may have twisted the axle, as it had tensioned the chain further.

I think the bearings and the cage the bearings are in are ok. As it free wheels fine, I can hear the click/ratchet type sound.
When it was off the bike with the wheel and tyre, I can hold the axle at both ends roll it along the ground and it is ok, lift it and free wheels fine.
I haven’t put the axle in a vice and turn the sprocket to turn the hub and wheel.
Only put the hub back on the bike and fit the chain and turn the pedal and it turns the wheel fine (I think, I can’t hear any abnormal sound).
If the end nuts are not very tight and I turn the cranks backwards it is smooth

So at the moment:
- The NTW and end nuts are tight on both ends
- The LHS cone does not turn (previous before the change, I can see it turn sometimes)
- The hub rotates fine on the LHS cone
- The darker cover and sprocket rotates around the hub
- Turning the crank forward the wheel spins fine
- Free wheels fine
- Turning the crank backwards is not smooth, it feels as if something is binding (the chain is not tight) and it does not sound right, some ‘clunking’.
- If I turn the wheel backwards, it turns the crank as well.
- I can see the sprocket moves very slightly when turning the crank backwards. (Maybe I need to tighten this nut more)

When I took the hub apart, the two 22mm flat nut were fairly tight on.
The nut on the drive side was even tighter (But I did not have vice to hold in place and used 2 spanners to undo the nuts.

When I did take the RHS nut and the smaller cone I can see ball bearing and it was all coated what looks like copper anti seize grease. Is this right?

That is all I took off/unscrewed (Plus the circlip to change the spring). I was going to take everything apart and clean, but I struggle to take the larger locking clip on the sprocket. So wiped around the bearings area and re/add grease (used weldtite TF2 lithium grease), then after 1st ride, cleaned and replaced with park tool high performance grease (blue stuff). So I’ve not accessed the planetry gears bits.

So it’s a little frustrating, putting this hub back on. I have had the wheel off to change the tyre and I remember the nuts (the two 22mm and the RHS nut) staying on and looked fairly secure and tight on.

I think you are right, in it needs a slight tweak. (hopefully)
I'll try again, starting from the RHS.
Thank you for your help

Brucey
Posts: 35195
Joined: 4 Jan 2012, 6:25pm

Re: SRAM A2 Automatix; introduction to the internals

Postby Brucey » 14 Jun 2018, 1:01pm

Col18 wrote:Thank you for your help and advice.
The bike has Non Turn Washers with the serrated face to lock/clamp onto the chain stay.


they are the least good form of such washers (they don't deserve the name NTW in my book) and have often proved to be 100% inadequate. Ones with tangs are much better. If you are not able to tighten the track nuts fully serrated ones definitely won't work.

How does the hub get ruined if the bearings/bearing adjustment is not aligned?


very simply with too much preload. If there is no locknut on the RHS, the cone isn't tight against the shoulder on the axle, and you adjust all the slack out of the bearings, when you tighten the track nuts the cone moves ~0.1mm and the bearings see a massive load which they are not designed for. If you are making the hub draggy like this then it is almost certainly being badly damaged.

The first and second re-fitting, the axle had twisted after a cycle, I don’t think it was spinning when I was pedalling. It needed a lot of force to unscrew the end dome nuts. I assume a larger force (going up hill?) may have twisted the axle, as it had tensioned the chain further.


If the track nuts are not tight (use a torque wrench if in doubt whether your tight is the same as other people's) the wheel can move wholesale and/or the axle can spin. If the axle spins the bearing adjustment can become preloaded enormously, because the axle tries to spin CW in top gear and it can wind itself through the LH cone/locknuts. I have seen a steel-shelled Sachs hub split lengthwise because of this; needless to say the crappy serrated washers were not good enough and had proper NTWs been fitted this wouldn't have happened.

Reassemble the hub according to the instructions in my previous post and try that. I advise most strongly that you would be much better off using NTWs with tangs on rather than the serrated ones; they are almost useless by comparison. If the bearing adjustment is changed by doing up the track nuts then there is definitely something wrong.

If in doubt, take the wheel/bike to someone who knows what they are doing and get them to check it/adjust it.

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~

Col18
Posts: 21
Joined: 13 Jun 2018, 3:23pm

Re: SRAM A2 Automatix; introduction to the internals

Postby Col18 » 14 Jun 2018, 2:06pm

Thank you Brucey for taking time to advise and help.

Will re-try again.

How do I tell if the hub is ruined? Is it ruined on the body were the spokes are attached to?
Does it wear away the groove the the bearing rest in?

I cycled the bike home yesterday and it seemed ok. Getting home time wise and speed wise seems normal.

But when I got back, turning the crank backwards by hand, it was not smooth.

It free wheels but I think it does not free wheel as long as before. I hope it is not damaged now.

Col18
Posts: 21
Joined: 13 Jun 2018, 3:23pm

Re: SRAM A2 Automatix; introduction to the internals

Postby Col18 » 15 Jun 2018, 9:57am

I re-looked at this last night.
It's fixed/assembled properly (I think)

Took covers off, check bearing were ok and grease was still there.

The nut that goes over RHS Smaller cone that goes into the hub around axle, the nut was tight, but the axle had a 1-2mm movement. I could not tighten nut further (no vice, done by spanner/wrench), if you pulled the axle it would move about 1-2mm and you can see little bit of the copper grease.

LHS with the 2no 22mm nuts, I put the first one on and screwed it so not too tight on the cone/cover. Put the second nut tight onto the first nut.
I held the axle and turned the sprocket forward. no issue. Turned the sprocket backwards and it started to spin smoothly then I can see (like you mentioned) the first inner nut winds it in and is tighter onto the LHS cone/cover.
So I loosened both nuts, adjusted the first nut (winding it out very slightly), and put the outer nut back on against the first nut. The cone/cover turns around the hub, but does not move laterally too much, (less than 0.5mm i think). Turned the sprocket backwards and span smoothing without the nut winding in.

I put the wheel put on, tightened the track nuts (I think I will get better NTW)
Pushed the crank backwards hard.....the smooth sound of gears/chain. Crank span a few rotations. It sounds smooth as well.
The inner 22mm nut does not wind itself onto the LHS cone/cover.

I need to test this with a ride, at the moment it spins really smoothly on a bike stand.

Hopefully it hasn't been damaged, I know on the first two attempts, if it was hard to turn the pedals backwards, I would stop and re-look.

Thank you for your advice Brucey. it definitely helped.

Brucey
Posts: 35195
Joined: 4 Jan 2012, 6:25pm

Re: SRAM A2 Automatix; introduction to the internals

Postby Brucey » 15 Jun 2018, 10:11am

Col18 wrote: .... if you pulled the axle it would move about 1-2mm and you can see little bit of the copper grease.....


copper grease.....????

This is not for use on any bicycle bearings of any kind; please tell me you have not been putting this inside the hub....?

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~

Col18
Posts: 21
Joined: 13 Jun 2018, 3:23pm

Re: SRAM A2 Automatix; introduction to the internals

Postby Col18 » 15 Jun 2018, 1:06pm

It looked like that inside when I took the nut and smaller cone off.
The inside edge of the cone has this colour as well.
(I hope it is not rust, or muck!), but to me it looked like copper grease, and it was copper colour.
I took photos as I dismantles the hub, but I did not take a photo of this area.
I might take apart again if I'm confident enough (I've spent 4 evening trying re-assemble/re-adjust this) and take a photo.
The bike came with this hub, it is over a year old, may be SRAM change the grease type here?
It is my commuter bike and I clean it down if very mucky, using a water hose, (using the stream setting, not jet).

When the cone was off, I can see ball bearing, closer together in a cage. I couldn’t/was not confident to take the ‘sprocket carrier’ held by a ‘lock ring’(correct term?).
(didn’t want to prise this off and break something).

The hub spins nicely now. (for now)

Brucey
Posts: 35195
Joined: 4 Jan 2012, 6:25pm

Re: SRAM A2 Automatix; introduction to the internals

Postby Brucey » 15 Jun 2018, 8:19pm

it is probably corrosion then. I recommend using the kind of SFG that is used in land rover front swivels, because this has anti-corrosion additives in it and gets around the hub nicely. Use a heavier grease in the wheel bearings themselves.

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~

Col18
Posts: 21
Joined: 13 Jun 2018, 3:23pm

Re: SRAM A2 Automatix; introduction to the internals

Postby Col18 » 17 Jun 2018, 9:41am

I opened up the hub. A bit more confidence and now know how to set and assemble the LHS cone.

I put more park tool grease.

Opened the RHS nut and cone.
See photos.

It does as you say look like corrosion. There is muck inside, I used a small dia metal and picked out bits of copper colour muck.
It might be thick grease and corrosion??

Is it easier to remove the sprocket (by taking off the lock ring?)

Or can access be from LHS if the larger e circlip is removed?
Image Attachments
20180616_191342-2064x1161.jpg

Brucey
Posts: 35195
Joined: 4 Jan 2012, 6:25pm

Re: SRAM A2 Automatix; introduction to the internals

Postby Brucey » 17 Jun 2018, 9:59am

removing the sprocket doesn't give you improved access to the RH hub bearing. You can pry the dustcap out of the driver and remove the bearing clip that way, but TBH the damage doesn't look that bad, and the dustcap may be damaged in the process. I would suggest that just whacking in a load more grease (with better corrosion inhibitors) will keep it happy for a fair while.

I suggest that to keep the whole hub (except the LH ball race) lubricated it is easy enough to remove the RH cone from time to time and add a load of SFG to the hub. This will work its way through the hub internals and keep them happy.

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~