Road bike maintenance - gears
Time: Allow about three hours to replace chain, cassette and cables and adjust, clean and lubricate the gears.
Difficulty: Basic adjustments are easy; more skill is needed if replacements are needed.
- Cable cutters
- 5, 6mm Allen keys
- Chain tool
- Small file
- Rohloff, Park or other chain checking tool) or metal ruler
- Small cross head screwdriver
Before attempting the main servicing as described below, clean your derailleur with a de-greaser and when dry use a PTFE or Teflon based lubricant on the pivots. Wipe off the excess after you have finished.
When dealing with shifting problems it is essential to consider the transmission as a whole. Shifting will never be sweet with a worn cassette, worn or unduplicated chain. Cable condition is also all-important.
If the chain 'skips' on the sprockets this indicates that the sprockets, or both sprockets and chain, are worn.
By replacing the chain before it is too worn, you can extend the useful life of your cassette sprockets.
Only replacing the chain will normally result in the chain jumping on the worn sprockets. If you replace the cassette, it is worth renewing the chain at the same time; otherwise the old chain will wear out your expensive new sprockets very fast.
If you continue to have rear derailleur shifting problems after overhauling your rear derailleur system, take your bike to a good bike shop. The shop should have a special tool to check the alignment of the gear hanger.
Though we describe shifting to large chainwheel to large sprocket and small chainwheel to small sprocket during the gear adjusting you should avoid riding with the chain in these combinations - the extreme angle of the chain will cause more rapid wear to the chain, chainwheels and sprockets.
Removing the cassette
Replacing the cassette
- Remove the wheel from the frame and remove the quick release skewer.
- Slide the correct lock ring tool into place on the lock ring. (Check that tool's splines engage properly in the splines of the lock ring).
- Re-fit the hub's quick release (without its conical springs) through the tool and the hub and tighten it almost completely, to ensure that the lock ring tool is held securely in place.
- Working from above, position a chain whip on the left side of the second largest sprocket so that you are pushing down and trying to turn the sprocket clockwise.
- Turn the lock ring tool with a large adjustable spanner anti-clockwise by pushing down on both tools.
- Remove the quick release skewer and spin the lock ring tool to remove the lock ring.
- Lift off the smallest sprocket and lay it out on the bench followed by any shim.
- Continue with the rest of the cassette.
- Most older Shimano cassettes will have the last five or six sprockets bolted or riveted together.
- Campagnolo eight-speed cassettes are made up of individual sprockets and spacers whilst Shimano nine-speed and Campagnolo nine and ten speed cassettes have the larger sprockets generally grouped in twos on a 'spider'.
Chain checking and removal
- Lay out the new cassette alongside the old one carefully noting the correct position of the spacers and orientation of the sprockets.
- Hold the wheel horizontal and slide the cassette sprockets onto the hub, starting with the largest first, with a spacer in between each one.
- Shimano cassettes have a triangular mark on top of the cassette body that needs to be aligned with the widest spline.
- For Campagnolo eight speed cassettes, align the sprocket's diamond mark with the narrow spline on the.
- Check that all the cassette sprocket size markings are face upwards on the hub and that the spaces between the sprockets are even.
- The last sprocket fitted should sit just proud of the freehub body - if not you may have a spacer missing!
- Screw the lock ring loosely into place with its tool by using your fingers.
- Refit the quick release skewer without its conical springs.
- With the lock ring tool and adjustable spanner tighten the lock ring.
Assessing chain length
- Clean the chain with a degreasing agent.
- Check it for wear using either:
- A chain wear tool
- Or pull the chain taught over your ruler. Each link is exactly 1/2" long (rivet centre to rivet centre). If 24 links measures 308mm (12 1/8in) or longer, your chain is worn and should be replaced (if so, then the cassette will probably need replacing too).
- Shift the chain onto the smallest chainwheel and rear sprocket.
- Fit the chain link extractor so that the chain lies in the furthest slot from the screw handle.
- Line up screw pin in the tool and the rivet in the link. Turn the tool handle until it pushes the rivet 80 to 90 per cent of the way out of the chain.
- Unscrew the tool to retract it from the chain and then grasp the chain either side of the link and bend the chain gently to separate the chain.
- With modern Shimano HG and IG chains (but only these!) you need to push the rivet out completely.
- You can now remove the chain from your bike.
- Shift the rear derailleur under the largest sprocket and the front derailleur over the largest chainwheel.
- Now feed the new chain (inner link end) into place up around the largest chainwheel (through the front derailleur), over the largest rear cog and then thread it over the top and in front of the first pulley and behind the lower pulley.
- Pull the other end of the chain (outer link end, usually with a rivet sticking out) tight against the inner link end such the rear derailleur cage is almost horizontal.
- Mark the nearest outer plate and add two complete links. Shorten the chain to this point.
Stiff link correction
- Remove any surplus chain links (as described in 3. above).
- For standard chains (not Shimano, Campagnolo 10-speed, SRAM Powerlink - see below) push the two halves of the chain together, letting the slight protrusion of the chain rivet on the inside link snap the two ends together.
- Place the chain on the furthest slot of the extractor with the rivet pointing towards the chain tool handle.
- Carefully close the chain link tool's pin onto the head of the rivet.
- Continue tightening it until the rivet starts to push through the second outer chain link.
- Check that the pin is aligned with the hole in the chain link and continue tightening until the rivet is protrudes an equal amount each side of the outer chain link.
- With modern Shimano HG and IG chains remove the surplus length of chain as above, but push the rivet out of the chain. To rejoin the chain, you need a special Shimano connecting pin. Slide it, pointed end first, through both the outer and inner links of the chain.
- Put the link into the furthermost slot of the chain tool.
- Tighten the tool's pin onto the rivet head and drive it into the two halves of the chain link.
- Continue tightening until the fatter rivet section of the pin protrudes equally either side of the outer link. Shimano specify this to be 0.2mm.
- Snap off the protruding guide section with a pair of pliers.
- Campagnolo ten-speed chains require a special tool. This is expensive, so it's probably best to leave this job to a suitably equipped local shop.
- Some SRAM chains have a special Powerlink for easy 'no-tool' chain removal and fitting.
- To dissemble, slip the chain off the chainring to release all tension from it.
- Slide the chain ends together and firmly press both plates of the connecting link towards one another to remove the two halves of the link.
Checking rear derailleur and its operation
- Whatever the make of chain, it is possible that the link just joined may be stiffer than the rest of the chain.
- A sure sign of a tight link when pedalling is a chain that jumps every two or three rotations of the pedals.
- If so, put the chain in the upper slot of the chain link extractor and tighten the chain link extractor pin about 1/8 turn to spread the outer plates of the link and remove the stiffness.
- Finally, check that the rivet ends still protrude a little beyond the outer link plates.
Cable checking and renewal
- Using a degreaser, clean off any crud from the derailleur pulleys and inspect for excessive wear.
- Most wear occurs on the pulley: check that the teeth are not badly worn and that it can move sideways about 3mm.
- Shift the chain onto the small chainring and small sprocket, grasp the gear mechanism and twist it - there should be virtually no play in the cage pivot or in the parallelogram pivots.
- Check that the mechanism is properly tightened onto the gear hanger, if it still rocks it will need replacing.
- Shift the gears one at a time, checking that each change is both smooth and sure on each chainring.
Adjusting the rear derailleur
- If the cables are more than a year or two old it is likely that both the inner and outer cables need replacing.
- Cables should definitely be replaced at the first sign of any damage or fraying.
- Check the inner cable for fraying at the shifter, all stops and at the derailleur.
- Check the outer cables too for excess bending or casing cracking particularly at the cable stops on the frame and where it enters the derailleur.
- Make sure that the outer cables already fitted are the correct length - not too long or too short. You should be able to turn your handlebars without the cables getting tight, and there should be no kinks in the cables.
- To remove your cables select top gear (smallest sprocket) and back off the adjustment on all the cable adjusters completely - derailleur, down-tube stop and shifters if fitted.
- Loosen the cable clamp bolt; pull the inner cable out through the shifter, making a note of where it was seated.
- Remove the old outer cabling - with Ergopower shifters it will be necessary to undo the top section of handlebar tape.
- To replace cables use the old outer cables as a guide to the outer cable lengths you need to cut. Allow enough length to avoid making the bends in the outer casing too tight (otherwise you may find that either your bike changes gear automatically when you turn a corner or you may find that steering feels very stiff!) Don't leave cables too long either, as longer lengths are inefficient. Use sharp cable cutters to trim the outer gear cable. If the cable end gets slightly squashed, squeeze it back to a round profile with a pair of pliers. Trim the end (use a file) to get it as square and flat as possible and then open up the inner liner up a sharp pointer.
- Cable ferrules are essential - fit one to each end of the outer cabling. They are available in different sizes and should be a snug fit on the outer cable and a reasonably close fit in the stop.
- Slide the first length of outer casing into place on the shifter.
- Feed the inner gear cable through the shifter (on Ergopower shifters it is under the hood) and the outer casing as per the original.
- Slide the inner cable through the frame stops and into the outer casing by the gear mechanism, checking that all ferrules are properly seated in the shifter, frame stops and at the gear mechanism.
- Feed the inner wire the correct side of the derailleur clamp and pulling the inner cable reasonably taut with a pair of pliers, tighten the clamp bolt onto it.
- Using a pair of cable cutters, trim off the inner cable about 3cm beyond the clamp and crimp on a cable end to prevent the cable from fraying.
To adjust the cable tension on a Shimano rear derailleur
- All derailleur gear mechanisms have 'limit screws' which control the distance the gear can move inboard and outboard.
- On Shimano gears these screws are generally on the rear face of the derailleur. The top screw controls the outward movement of the gear (towards the smallest sprocket)
- On Campagnolo gears they are usually on the front face of the gear. The lower screw controls the gear's outward movement.
- Adjust the screw such that the upper derailleur pulley wheel is in line beneath the smallest rear sprocket. Shift onto the next sprocket and back again. The chain should shift cleanly without hesitation. If it doesn't, back off the screw 1/8 - 1/4 of a turn. If it still remains hesitant check that the inner cable is not too taught preventing the shift onto the smallest sprocket.
Finally adjust the low gear limit screw
- Select top gear and turning the pedals forward, select the next gear.
- If the chain doesn't move smoothly to the next sprocket turn the adjuster on the back of the gear mechanism anti-clockwise half a turn at a time until the chain moves cleanly to the next largest sprocket.
- Select the next largest sprocket and check that the chain will move cleanly to it.
- If not, turn the cable adjuster anti-clockwise a further 1/4 of a turn at a time until the change is clean.
- Check that the upward shifts are still OK. If not, back off (turning clockwise) the cable adjuster until the shifts are correct.
- With Campagnolo rear derailleurs
- Shift onto the fourth smallest sprocket and adjust the cable tension adjuster so that the pulley is positioned perfectly centrally beneath the fourth cog.
- Turning the cable adjuster anti-clockwise moves it more inboard, turning clockwise moves it outboard.
- Shift to the fifth smallest sprocket. If the change is slow or hesitant, or if the top pulley is not perfectly lined up with the sprocket, turn the adjuster 1/4 of a turn anti-clockwise.
- Check the shift in the reverse direction. If it is slow, turn the adjuster back (clockwise) 1/8 of a turn.
Adjusting the front derailleur
- This controls how far the derailleur moves inwards for the largest sprocket.
- (Lower screw on Shimano gears, upper screw on Campagnolo).
- Turn the screw a 1/4 of a turn at a time until the shifting onto the largest sprocket becomes hesitant.
- Back the screw off 1/8 of a turn at a time until the shifting is clean.
- Make sure that your gear will not overshift and send either the chain or the gear mechanism itself into the spokes.
- When in the largest sprocket the gear must clear the spokes by at least 3-5mm (Wheels do flex under load - especially when climbing).
- Clean the derailleur and apply just a little lube to the parallelogram pivots.
- The derailleur cage should sit about 2-4mm above the teeth of the outer chainring.
- Looking from above, the outer cage plate should be parallel with the chainrings. Undo the seat-tube clamp bolt at the side of the mechanism and turn the cage to line it up and re-tighten the bolt.
- Shift the chain on to the largest rear sprocket and smallest front chainwheel.
- Adjust the low limit screw so that under repeated shifting from the largest to the smallest chainring the chain shifts without hesitation but does not overshoot the small chainwheel inwards.
- Reset the cable tension with the chain on the smallest chainwheel until it is just taut.
- Shift into the smallest rear cog.
- Repeatedly shift onto the biggest chainring - adjusting the high limit screw until it does so without hesitation but does not overshoot the largest ring or catch on the crank.