How to change your chain and sprockets
26 June 2014 11:00
Even a beautifully maintained chain that spends its life in a shimmering coating of oil and is frequently adjusted to exact manufacturer tolerances will wear out, and it will take the sprockets with it.
The chain stretches with miles, its rollers fit less snugly inside the sprocket’s teeth and cut into them, eventually turning each tooth into a pointed hook.
You’ll know a chain needs replacing when it requires more frequent lubrication and adjustment, or you notice stuck links, which are known as tight spots. If you feel a lack of smoothness when changing gear, check your chain for wear and tight spots.
You should always replace the sprockets at the same time as the chain. Running a new chain on worn sprockets will cause rapid wear, leaving you needing to replace the chain again in very short order, so it’s a false economy to replace just the chain.
Before you embark on this job, make sure you are familiar with the technique for breaking and re-fitting a chain’s rivet link, and have the tool to do the job.
You will also need sockets big enough to undo the front and rear sprocket nuts, which are often bigger than those in standard socket sets. Also, order a replacement tab washer to add security to the front sprocket nut.
When replacing your chain and sprockets, consider altering your bike’s gearing. Fitting a front sprocket that’s one tooth smaller or larger will give you more or less acceleration respectively, at either the cost or gain of some top-end speed.
Fitting a larger back sprocket will give more acceleration, while a smaller one will reduce it. This is a finer adjustment than the front sprocket, with a difference of three teeth in either direction having the same effect as changing by one tooth at the front sprocket.
You'll need a new chain and sprockets (obviously), chain splitter and a link riveting tool.
1. Make sure you have a clear working space. The first thing to do is place the bike on its centrestand, or a paddock stand, so you can remove the rear wheel when it comes to replacing the rear sprocket.
2. Check if the gear lever needs to be removed before the sprocket cover is removed. Note the position of the splined boss that bolts to the shaft before you remove it. Now remove the the front sprocket cover.
3. Front sprockets are secured with a big nut which can be self-locking, or it may have a tabbed locking washer. Tap back the tabs with a flat screwdriver or punch and hammer. Have a new washer ready for later.
4. You need to prevent the force being applied through the sprocket nut turning the back wheel. Wrap a piece of hard wood in soft cloth and insert it through the back wheel (take care not to trap the valve).
5. When removing the front sprocket nut, use a breaker bar. When you have the nut undone make a note of which way it is fitted, sometimes there is a shoulder on one side. Leave the front sprocket on for now.
6. Remove the rear wheel and lay it flat on the floor with the sprocket facing up. Undo the sprocket nuts and remove. Compare the old and new sprockets for fitment and size. Now fit the new sprocket.
7. Compare old and new front sprockets for fit/size. With the wheel still out, which will make it easier to manipulate the sprocket as there’s no chain tension, fit the sprocket and wrap the old chain around it.
8. Loosen the chain adjusters a couple of turns. This will help when refitting the wheel because the new sprockets will tighten the old chain. Refit wheel with the old chain on, don’t tighten the spindle nut yet.
9. Split the chain, using a splitter tool. Loosely join the two chains together. Pull the old chain from the front sprocket until the new one is around both sprockets. Join the new chain with the riveting tool.
10. Fit the tab washer and front sprocket nut, re-insert the wood into the wheel and tighten the nut to the correct torque setting. Tap the tab on the washer over the nut. Now tension the chain and tighten the spindle.