With 25 per cent of the United Kingdom commuting by bike, the ability to repair one might come in handy. Whether you need to fully replace a broken hub gear or want to upgrade one, it is a simple project anyone can do. The exact process varies depending on the model of your bike.
Remove the Rear Wheel
Place the bike in first gear to release tension on the cable running from the gear shifter. It is important not to change gears on the bicycle while replacing the hub gear. To begin, locate the hub gear on the rear wheel. The gear selector is on the exterior of the gear hub. Keep track of all bolts you remove because each one needs to go back. Once all bolts are loose, the gear selector should pop off. Remove the interior pin. The wheel nuts on each side should be exposed. Use a spanner to remove both nuts. Slide the wheel out and remove the chain.
Remove the Cassette and Axle
Hold the sprockets when removing the cassette. Once secure, insert a cassette spline tool into the lock ring. From there, use a spanner to loosen the lock ring. The cassette will slide off. To remove the axle, use a spanner to first remove the lock nut, then the cone on the non-drive side of the wheel. If you plan on reusing your bearings make sure they don't get loose. Note the order of any spacers or washers. They need to be replaced in the same order. Use a pair of needle nose pliers to remove the bearings from the hub.
Remove and Reinstall the Freehub
Use an allen key to unscrew the bolt and the freehub should come off. Grease the body bolt and secure the new freehub in the wheel hub.
Replace the Cassette and Axle
Clean out the cones, hub interior, and axle to slow down the wear on the bearings. Add a layer of grease inside the hub where the bearings will be placed, and then carefully insert them. Cover the bearings with another layer of grease to prevent them from coming out. Replace the axle through the drive side of the wheel. Wind the cone on the non-drive side and replace spacers or washers. Now tighten the cones, but be careful not to crush the bearings inside. Finally, slide the cassette back onto the freehub body. Grease the threads of the lock ring and secure the cassette.
Reattach the Wheel
Slip the chain back onto the gear hub, and then slide the wheel back into place on the bike. Replace the wheel nuts on both sides of the wheel, then replace the interior pin and gear selector. Tighten the bolt on the gear selector and you have successfully replaced the hub gear. Give the wheel a few spins to make sure it works.