Oops!

July 12, 2012 7:48 AM

So, um, how do you put a bicycle hub gear back together?

So, following this question, I bought myself what I hope will be my first flipper bike. It's an unpretentious but rather handsome three-speed from the '70s, a nice, comfortable, practical ride of the sort that I see all over New Orleans every day. Minor rust, needed some re-lubing and adjusting and general cleaning up, no big deal. Excited to turn it around and get it into top shape, I set to work immediately.

Everything went well with the servicing except for one teeny little thing. While working on the back wheel, I decided (perhaps foolishly?) to open up the three-speed hub bear and see how things were doing in there. I started disassembly (which was straightforward enough) and as I was separating the two halves of the hub, I heard the dreaded *clink* of a small piece of metal falling out of the inside of the hub and hitting the ground.

It didn't look like it had broken off of anything, but it was a mysterious object. The piece that came out was about a centimeter long, perhaps three millimeters in cross-section, and had a D-shaped cross-section with one flat side and one round side. I was unable to find a definitive location for where it ought to have come from – the axle has a cut-out in it that seems like it *might* be the place that it came from, but what it might have been doing there and what its purpose was I do not know. I stuck it back into where I thought it most likely belonged with a bit of grease, reassembled the hub, and finished working on the bike.

Except I didn't get it right, because now the darn thing won't shift gears. I'm not 100% sure that this is down to the piece that fell out, but it may be. There's a pin that is supposed to be actuated inside the axle by a mechanism attached to the shifter cable, but that pin won't move anymore. I may have blocked it or gotten something wedged somehow, I'm not sure. I intend to have another look inside there at the earliest opportunity, and I've been looking online for any how-tos on the dis- and re-assembly of old bicycle hub gears, but I'm not finding much. I could use some advice on how best to proceed. Help me out, MeFites! How do I undo this and salvage the bike from the ignominy of becoming an accidental single-speed?

posted by Scientist to travel & transportation (16 answers total)

Go down to your local bike shop with all the parts and either ask them to put it back together correctly or get them to photocopy the appropriate pages from their Sutherlands manual.

If you send me pictures of all the writing on the hub I might have the correct diagrams in my older copy of Sutherlands.

Good luck, 3 speed hubs are fun to work on.
posted by Confess, Fletch at 8:00 AM on July 12, 2012

Last time I took one of those things apart was about 35 years ago, and I too remember the sinking feeling associated with just catching sight of a tiny hairlike piece of metal winging its way to the far side of the garage.

Once I'd retrieved the little hair spring, I took everything apart and washed all the bits in kero and just sat down with it and figured out how it worked. It's intricate but eventually comprehensible, and working it out will give you tremendous respect for the engineer who originally designed it.

This exploded view shows you which things are supposed to go with which other things. Most 3-speed hubs will follow something fairly close to this pattern.
posted by flabdablet at 8:50 AM on July 12, 2012 [1 favorite]

Three-speed hubs are not like regular bike parts, they are actually more like clocks in disguise. Bring all of the pieces to a reputable bike shop, ideally one that's been in business a LONG time and has some geezers wrenching.

Or, alternately, you can tinker with it forever and if you're lucky you'll have a new skill when you're done.
posted by epanalepsis at 9:26 AM on July 12, 2012 [1 favorite]

flabdablet, I see my mystery part on that diagram! And I even figured out the right place to put it. Which means that either I put it in there incorrectly, it's come loose, or something else is wrong.

I am definitely of the "tinker with it until you figure it out" school when it comes to bikes (and most things, though I find bikes are pleasingly forgiving of this kind of behavior) though I may well see if I can scrounge up a copy of the Sutherlands Handbook at some point as it looks like an incredibly valuable resource to have. Taking it in to a shop to have them fix is probably not in the cards, as my goal is to sell this bike and so any money I spend is profit lost at the other end – and as MeFites warned me in my previous question, there isn't actually a lot of margin here.

Still, I had a grand old time sitting out on my back patio until 3AM last night tearing that bike apart and putting it back together. It rides 100% better than it did when I got ahold of it, and it looks better, and if I can just get the transmission working and fix that odd flat spot on the rear tire, it'll be perfect and I can ride it around for a couple of days to work out the kinks and then sell it on to a (hopefully!) happy buyer!

Thanks, MeFites. You have restored my confidence – I feel much better about being able to fix this issue than I did at the beginning, and as a bonus I'm going to get to learn how to work on hub gears! A valuable skill, as there are a lot of people in New Orleans riding hub-geared bikes.
posted by Scientist at 9:31 AM on July 12, 2012

If yours is an S-A (always a good first guess), as ever Sheldon is a good start.
posted by normy at 10:49 AM on July 12, 2012

The only vaguely D-shaped things I can see there are the pawls. Make sure the little hair spring is doing the right thing with the one you put back in.
posted by flabdablet at 11:00 AM on July 12, 2012

Also, those hubs are really supposed to be oiled rather than greased. Grease makes them quite draggy.
posted by flabdablet at 11:01 AM on July 12, 2012

Oh yeah, I oiled it, not greased it. I just used a dab of grease to stick that little bit in place cos' there was nothing to hold it otherwise. I bet I did it wrong. I bet I even know how to do it right now.
posted by Scientist at 11:33 AM on July 12, 2012

Did you try you-tubing it? There are some great bike videos on there and, yeah, this three speeds are crazy hard to work on!
posted by fshgrl at 11:41 AM on July 12, 2012

If there was no hair spring holding the pawl in place, and no tiny axle for it to swing on, then you might be dealing with an SW hub that has springless floating pawls. Or there might still be bits on your garage floor you haven't found yet.
posted by flabdablet at 12:11 PM on July 12, 2012

OK, so I highlighted the bit in flabdablet's diagram that fell out when I was taking the hub apart. Here's a link: it's got a yellow box around it. What the heck is that, and how is it supposed to be installed in the hub? I *think* everything else went back together correctly. If I'm reading Sheldon's website correct, the pawls are the bits that swing out to engage the gears (or let them slide by, if coasting) and I know those didn't get disturbed. I didn't fully disassemble the hub, I just opened it up to see if everything looked OK, which it did except that I broke it, and added a little clean oil. It didn't seem like taking every little bit apart was warranted, and there were certainly more bits than I would have been able to deal with at the time.

Anyway, what's that little thingum? Does it have a name?
posted by Scientist at 12:32 PM on July 12, 2012

If yours is a 3-speed S-A AW, I think that might be your axle key. The indicator rod screws into it. It sits in the thrust ring which in turn drives the clutch and the gear change mechanism. Mr Brown again.
posted by normy at 5:49 PM on July 12, 2012

Yeah, that's the pin that connects the shift ("indicator") rod to the shift clutch, and the proper fitting of these parts is indeed crucial to gear shifting.
posted by flabdablet at 8:01 PM on July 12, 2012

HALLELUJAH WE HAVE A THREE-SPEED! Dear elder gods, that was a pain in the ass. Turns out that the hub in question was a Shimano 333, which in addition to not being quite so nice as the Sturmey-Archers of its day is also a special pain to work on even by the standards of three-speed gear hubs.

The darn thing has not one but two axle keys, the second of which I didn't even know about when I made this post because it was still lost in the bowels of the hub. It eventually fell out just when I thought I had figured out how everything went together, sending my heart to my stomach and me back to the drawing board. Here is a diagram that gives a good idea of how everything goes together.

I did eventually get it put back together properly after many, many attempts and it's back on the bike and it shifts beautifully. Well, as beautifully as a 40-year-old piece of machinery could be expected to shift. Thankfully I didn't see any signs of damage inside the darn thing while I was working on it, which is good because the old Shimanos are apparently known for occasionally breaking pawls (which is why they aren't as highly thought of as the S-A hubs) and then eating themselves. No sign of that here, though – everything appears to be in excellent shape, my hamfisted fiddlings notwithstanding.

The bike is working great now. Shifts, stops, not a squeak or a complaint, comfortable and fast and sturdy and rust-free – quite the opposite of how it was when I found it. I'm rather proud of myself, I must say! I just need to re-seat the rear tube now as it's a bit wonky and then I'll ride it for a couple of days, fix any kinks, give it a cleaning and a coat of wax, and put it on sale! I hope I can get a decent price for it.

Thank you everyone for your kind and patient advice. I would not have been able to fix this without you. I have, as predicted, learned a great deal about gear hubs and now feel much more confident fiddling with such things in the future. I love bikes so much.
posted by Scientist at 9:44 PM on July 14, 2012 [1 favorite]

a special pain to work on even by the standards of three-speed gear hubs

Special pain? I'll show you special pain. Apparently though those things are reliable enough that you don't actually have to get inside them as long as you just keep changing the oil.

I used to lust after owning one of those until I found out about these. My Big Dummy was built with one and I like it a lot.
posted by flabdablet at 10:35 PM on July 14, 2012

Dude, I wish I could even dream about one of those. Anyway, this'll have to be my last update lest this descend into chatfilter and GYOB territory, but I'd like to thank you specifically flabdablet for sticking with me all the way through this problem. The thing I love about bikes is that there's almost nothing that can go wrong with one that can't be understood and fixed with enough time and patience – but it really helps to have someone knowledgeable to lend their experience and encouragement. Thanks.
posted by Scientist at 11:01 PM on July 14, 2012