Hub gears often make people particularly nervous about the possibility of having a rear wheel puncture. Follow the instructions below and you needn’t worry.
It’s isn’t always obvious how to disentangle the gear cable enough to get the back wheel on, or how to reattach the gears once you’ve successfully repaired the puncture. It’s a little different to the procedure for derailleur gears, but luckily can be done with a minimum of tools. The main difference between hub gears and derailleur gears is that the gear cable is actually attached to the rear hub, so it has to be wriggled free before the wheel can be removed. Be warned though, there’s a slight added complication when refitting the wheel too – the position of the rear wheel in the frame needs to be set in such a way that the chain has the right amount of tension.
Step 1: Take a moment to look into the gap between the rear wheel and the frame while you change gear. You’ll be able to see the cassette joint stepping around the hub as you shift gear. Once you can see the effect that changing gear has on the cassette joint, set the shifter so that the cable is in its slackest position, where the indicator is pointing at gear 1.
Step 2: This is the most important step and the one that everybody misses out. It’s essential that, when you come to refit the cable, it’s correctly routed. However, once everything’s come apart, it’s not obvious how it goes back together. Take a moment to look at the cassette joint from behind and trace where the cable goes, so that you can put it back there later. If you haven’t got a photographic memory, make a sketch.
Step 3: Look at the cassette joint from behind. You’ll see a tiny hole, just below the cable clamp bolt. It’s just the right size for a 2mm Allen key. Poke the key into the hole and use it as a lever, gently turning the cassette joint anticlockwise to create slack in the cable. It can be tempting to do this with your fingers, but don’t as the spring inside the hub is strong and, if you slip, you’ll definitely end up with sore fingers.
Step 4: Keep the Allen key in position, holding the cassette joint. This gives you enough slack in the cable to pull the gear outer casing gently to the right and out of the end of the cassette joint, as shown. There should now be enough slack to pull the inner cable out of the slot in the cassette joint. Release and remove the Allen key.
Step 5: You should now have enough slack in the cable to allow you to wriggle the cable pinch bolt completely free of the cassette joint. Note which way it sits before you release it so you can get it back into the same place afterwards. You’ll have to use both hands to twist the cable, easing the pinch bolt out of its slot. Take care not to kink the cable.
Step 6: This leaves the gear cable completely free of the back wheel. With V-brakes and cantilevers, release the brake cable. If you have hub brakes, remove the bolt that holds the hub brake arm onto the frame/fork. It’s essential to remember to refit these when you come to refit the wheel. Undo the wheel nuts on either side of the frame and slide the wheel forward and out of the dropouts.
Source : BIKE MAINTENANCE TIPS, TRICKS & TECHNIQUES
See also bike maintenance tips, tricks and techniques “Adjusting hub gears”