To overhaul a coaster-brake hub, first take the rear wheel off the bike. If taking the wheel off seemed like a huge hassle to you, consider taking your brake problem to a good bike shop. If taking the wheel off was easy and got you all curious about what kind of a spiffy mechanical puzzle you were going to find inside the hub, then you are probably what they call “mechanically inclined” and you’ll probably do fine on this overhaul yourself.
Before you start wildly unscrewing all the things that keep the guts of the hub inside there, though, pause a sec, clean up your work area, clean the hub off, and figure out a way to hold the wheel still while you’re working on it. A brake hub has quite a few little parts in it, and if they get dirty or out of order before you put them all back together, the hub will not work right later.
So, start by cleaning all dirt and gunk off the outside of the hub. If you’ve been out riding in the swamps or cruising the sand dunes, it may even make sense to take the wheel to a do-it-yourself car wash and blast the gunk off with a hot water jet. Then take a stiff wire brush and clean out the threads of the axle ends as well as you can. This will make all the threading on and threading off of small hub parts easier during the overhaul.
Next, lock the brake arm tightly in place on its end of the axle. This is done by holding the arm still with one hand and getting a wrench that fits snug on the locknut, then tightening that locknut hard against the brake arm. If the locknut is just a thin one, unscrew the axle nut, get about four thick washers that will fit around the axle, then tighten the axle nut back down, so it can help hold that brake arm tightly in place.
Now hold the wheel flat, so the brake arm end of the axle is sticking straight down, and clamp the nut that is at the lower end of the axle in a vise. You got no vises? Good for you. A C-clamp will do the trick. Just hold the wheel flat at the corner of a table, so the brake arm end of the axle is sticking straight down past the corner, and the brake arm itself is resting on the corner of the table. Then clamp the brake arm firmly with a C-clamp. If you not only have a vise, but a slick two-hole, axle-vise tool, you can just stick the end of the axle into the big hole of the vise tool and tighten the vise up on it.
OK, one way or the other you have your wheel held in place horizontally, with the end of the axle that doesn’t have the brake arm sticking up. That’s how things are arranged in Figure 2-13. Take the axle nut off that upper end of the axle, holding onto the wheel and brake a with your free hand to keep things still. The axle should not spin, even if the threads on it are a bit rough. If the axle does spin when you turn the nut, you haven’t locked the nuts on the other end tight enough. Go back and do that over.
Put the axle nut down on a clean rag on your work bench or table or whatever, at one end of the rag, so you can line all the other brake parts up next to it as you take them off. If there is a serrated washer under the nut you just took off, take off the washer and place it next to the nut, with the bumps down, just like they were when the washer was around the axle. That way, when you go to put the washer back on the axle, you won’t have to wonder which way is right-side up.
Next look closely at the sprocket and the shiny dust cap that is just under it. Do they look OK? No bent or chipped teeth on the sprocket? No cracks or bent-out places on the dust cap? Is the ring spring tight in its groove? If those things are all OK, and your chain hasn’t been skipping due to the sprocket being extremely old and worn down, then skip the next two paragraphs and get on with the brake overhaul.
If your sprocket or dust cap is shot, you have to take the sprocket off. Get a skinny-ended screwdriver and stick it between the ring spring and the fat driver it is stretched around; there are little crescent-shaped gaps cut into the side of the driver where your skinny screwdriver tip will fit easily. Pry one end of the ring spring out from the driver, then move on to the next gap, so the spring will work its way out of the groove from one end to the other. Hold your free hand above the spring, like a shield wrapped around the end of the axle, so the spring can’t leap up and poke your eye out, or fly across the garage and roll down the driveway headed for the land of never-never.
When the spring is off, take off the sprocket and the dust cap, and place them on your clean rag, with the same side facing up that was facing up on the wheel. Get the replacement parts you need, making sure they are exactly the same as the originals, and put the dust cap, sprocket, and ring spring back around the driver just the way they were before. Make sure the sprocket is “dished” the same way it was before. Wonder how you get that ring spring stretched on there? Just start one end in the groove, then work your way around the spring from that end, holding the other end of the spring down and prying with the skinny screwdriver at each little crescent-shaped gap so the spring stretches out and around that fat driver.
2-13 Coaster-Brake Hub
To proceed with the brake overhaul, loosen the locknut (that’s the next thing in line on the axle.) Take it off, and put it in line on your clean rag. Loosen the threaded cone that’s next on the axle, and put it next in line on the rag.
Next lift out the retainer of ball hearings. (If there is a thin dust cap holding them in, ply that out very carefully with a screwdriver, working around and the ring as you pry, to keep the little thing from getting bent.) When you get the retainer full of ball bearings out of the hub, put it right down on the clean rag, with the same side of the ring up that was up when the retainer was in place. Say, you’re making a pretty professional-looking row of parts on your clean rag! Keep things straight like that, and you’ll get a rewarding feeling when you put the wheel all back together and it works perfectly, with no parts left over.
The next thing to take out of the hub is the driver and sprocket assembly. Hold the wheel hub down against the brake-arm end of the axle and turn the sprocket slowly ; it will spin right up out of the hub on its large helix threads. Set the whole assembly down on the clean rag, lift the large bearing retainer ring out of the hub shell, and put it down by the driver assembly.
Still holding the wheel in place? Good. Now lift it with one hand, slowly, and catch any loose brake parts that slip out around the brake arm as the rising hub shell clears them. On the type of hub illustrated, two or three brake shoes may come slipping down out of the hub. On other brakes, four little shoes might come tumbling out, or you may find that there is a whole stack of thin brake discs around the axle. That’s OK, just catch any brake shoes that do fall, and put them in a line on the clean rag.
Set the wheel’ aside, then slide the clutch cone up off the axle and put it in order on the clean rag. On different brakes there are clutch cones of all sizes and shapes, but they all have the big helix threads inside them, and they all pull the clutch tight when you pedal forward, and push over against the brake shoes or discs when you backpedal. You may want to put the driver and the clutch cone together right now, threading helix to helix , so you can figure out for yourself how the whole huh works. Get the idea? isn’t it slick?
After you’ve put the driver and clutch cone down on the clean rag, the only things left on the axle that you can take off are the clutch spring, and maybe (on some brake types) a pile of brake discs or a single brake spring washer.
Clean all of the parts, one at a time, including the bearings still on the brake cone, and the inside of the hub shell. Replace the clutch spring no matter what problem you had with your brakes. If your hub has both a clutch and a brake shoe spring, replace both of them.
Then check the helix threads of the driver and clutch cone to make sure they aren’t chipped or worn away. Check the brake shoes to make sure they aren’t worn smooth on the outer surfaces, bent, or marred by a little burr somewhere on the braking surface. If you have brake discs, see that they aren’t burred or glazed over with old, dry grease. Check the inside of the brake hub to make sure it isn’t all scored or marred by burrs. All those brake surfaces have to be perfect for the brakes to work right.
Take a steel ruler and line its edge up with the axle to make sure the axle isn’t bent. Look closely at the bearing dust caps and make sure none of them are bent. Check the bearings to make sure they aren’t pitted or worn flat.
Replace any parts that are wrecked. You may want to draw a little picture of any part you have to take to a shop; leave the picture of the part right in the place where the part went on your clean rag line-up, so you won’t forget how to set the thing back in place for quick reassembly.
OK, got all the new parts you need? Bet it was a pain finding them, wasn’t it? And a shock to learn how much they charge for some of those simple little things. Such is life.
Clean all the parts again, new and old, including the brake arm and cone assembly that are still attached to the axle. Use a safe but strong solvent for gunk removal, and after each part is clean make sure it stays clean until it is safely back inside the hub. A bit of grit in the wrong place inside a brake hub can totally ruin the thing. If the hub gets ruined, you’ll have to go through this whole process AGAIN. You wouldn’t want to do that, now, would you? So get anal.
Start the brake hub reassembly by spreading a bunch of good multi-use grease (beware: Some types of bike grease will glaze over at the high temperatures that build up inside a brake hub) on the bearings that are on the brake cone you left locked in place on the axle. Then put your NEW clutch spring in place.
Next you have to grease the brake shoes (or discs), hold them in place around the brake cone, slide the clutch cone down the axle until it nestles against the brake shoes, and finally slide the wheel over the whole business. This can be tricky. Use lots of grease on the brake shoes, and they may stay in place while you slide the wheel down over them.
You may even have to take the axle out of whatever device is holding it, turn the axle horizontal, then hold the brake shoes in place and slide the hub over them. However you do the trick, make sure the shoes wind up snug against the fixed brake cone, and lined up with the “key” bumps and the slanting faces of both the brake and clutch cones, so the brake shoes stay in place when the wheel is whirling around them. When you get the hub resting down flush on its bearings, hold it against them and turn it, peering down into the hub at the brake shoes as you do so. Brake shoes snug down against that fixed brake cone? Wheel sliding around them without any hang-ups? Good.
The wheel will wobble and wiggle as you turn it on just that single set of bearings, of course, hut the brake shoes shouldn’t flop around down in there, or get jammed cattywampus against the turning hub shell.
When you’re sure you have the brake parts lined up right inside the wheel, put the big retainer of bearings into its race in the hub shell, grease the bearings, and turn the driver assembly down into the clutch cone on its helix threads until it rests against the bearings.
Next put the small retainer of bearings into the race on top of the driver assembly, grease them, and spin the cone down the axle until it is snug against the bearings. Back it off a bit , hold it with one hand, and use the other hand to turn the sprocket as it would turn if you were pedaling the bike. Turn the sprocket, hold it still and let the wheel coast, then turn the sprocket the other way , as if you were backpedaling.
Do you feel a nice smooth application of the brakes? Does the wheel slow quickly and quietly to a stop? If not, take the cone, bearings, and driver assembly off the axle, and take the wheel off if you have to, in order to get those brake shoes and their cones in line so they coast and brake like they’re supposed to.
If you can’t get it together so it works when you put all the stuff on the upper end of the axle, take the wheel to a pro and ask him or her if you can watch the thing being put together so it will work. That way you’ll learn the tricks, and you won’t be afraid to take the thing on again if you have to later.
When the brake is working smoothly, tighten the threaded cone again by hand, then back it off about a quarter turn, or until you can just barely feel some play if you wiggle the rim of the wheel gently with your fingertips. Turn the locknut onto the axle and tighten it against the threaded cone. Try to get hold of a cone wrench that’s big enough to fit the cone and hold it still while you tighten the locknut, you can b sure the hub will keep the precise adjustment you have just given it. If the hub gets too tight, you can ruin the bearings. If it’s too loose, the axle may bend or the driver may fatigue and snap. So get it right.
Take the wheel out of the vise or whatever was holding it, then put the washers (if you have any) on both ends of the axles (serrated bumps facing IN, remember) and thread the axle nuts on .
Put the wheel on the bike. Then air up the tire and ride in peace. You’ve got good brakes again!
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