Here’s how to deal with a snapped rear gear cable which doesn’t split the chain or remove the rear mech.
There are two main places where the gear cable which goes to the rear derailleur can fail. One is under the cable clamping bolt and the other and more likely place is inside the gear shifter.
If the cable has failed within the shifter use these steps.
If the cable has failed within the shifter, the cable will have to be pulled through the outer gear cables from the rear derailleur. This is because on the end of the gear cable there will be a cable end cap that will tight on the cable which will prevent the cable being pull through from the gear shifter.
To pull the cable from the rear derailleur, the cable clamping bolt on the derailleur will need to be released using a 4mm Allen key.
With the gear cable removed, the high limit screw on the rear derailleur can be used to move the derailleur up the cassette. Therefore, putting the bike into an easier gear which would make it easier to ride home.
The high limit screw can be used by screwing it clockwise to force the high limit position up the cassette.
Using the high limit screw will only move the derailleur up the cassette by a few gears, however if it is a long ride home those few gears will make all the difference.
If the cable has failed elsewhere and not in the shifter, there is another method which can be used which can move the derailleur further up the cassette. If this is the case, follow these steps.
Remove the gear cable from the gear shifter. To do this change the gear shifter all the way down its range so that the hardest or smallest gear on the cassette would be selected. With the shifter in this position the head of the gear cable is exposed when the rubber hood is pulled back. Now the head of the gear cable is exposed, you can push the gear cable through the outer gear cables until the head of the gear cable leaves the shifter. The gear cable can now be pulled out of the shifter and off the bike.
Thread the gear cable through the barrel adjustor on the derailleur so that the metal head of the cable sits in the barrel adjustor and the rest of the cable can be threaded through the cable clamp bolt.
Push the derailleur up the cassette by hand so it sits under a specific chosen gear. The cable can be pulled tight and clamped using the cable clamping bolt. This will hold the rear derailleur in the position up the cassette.
The barrel adjustor can now be used to centralise the rear derailleur under the selected gear in order to make it run smoothly.
The excess gear cable can be rolled up tightly and hooked as best as possible over the derailleur.
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This repair has been carried out on a component from a popular brand. If you are using a different component please refer to the manufacturers manual to ensure specific details of the component/task are known. The principles and general skills of the task can be transferred but maybe not the exact details.