I wasn’t going to do anything on gear indexing because it’s a subject that’s frankly covered perfectly well over on Park Tool. However, I do have one neat little trick that I use when cabling up a rear derailleur, and that might prove useful to some of you…
So, start as you should when setting up the rear cabling with the chain on the bottom sprocket. One thing that Park and other manuals and guides suggest doing when cabling a rear mech is to wind the rear mech cable adjuster all the way in, and then back it out – usually two full turns – before pulling the cable taught and tightening the bolt on the mech.
Personally, I would go for a third full turn, and then do the following:
- With the uncut cable threaded through the rear mech, apply tension to pull the cable tight
- Whilst gripping the cable with your fingers, use your thumb to push against the ‘knuckle’ of the derailleur to push it a little inboard – there’s no need to go too far, but just apply enough pressure to move the mech towards the second sprocket on the cassette
- Now pinch the cable bolt tight
After doing this you’ll probably find that the rear mech isn’t indexed at all – it may even shift onto the second sprocket when you turn the pedals – but the cable will be nice and taught. Now, turn the cranks and wind the cable adjuster in until it shifts down onto the bottom sprocket and / or runs quietly and smoothly. From here you can fine tune the mech to shift beautifully.
I find this method means that there’s never an issue of a lack of tension in the cable, and avoids the lazy approach of winding the cable adjuster out until there is enough tension (which can often leave you without room to adjust as the cable stretches). With practice you can stick to the recommended two full turns and apply just enough pressure to the derailleur knuckle such that you may not even need to fine tune it – by using this method I now rarely need to tweak a rear mech by more than a quarter or half turn on the adjuster.
And there you have it – my favourite, personal trade secret laid bare… damn it!