Making your own gear cables will save you a lot of money and by stocking up on the items required you'll never be left with crappy shifting or having to run down the local bike store and pay through the nose.
Quick and precise gear shifting is all about having free running, undamaged cables and outer casing. The more you ride in wet or dusty weather, the quicker your shifter cables crap out.
I've found that regreasing cables seldom works. The only thing that results in a guaranteed return to shifting perfection is replacing the inner steel cables, cable outers and cable ferrules. A shift cable kit with everything you need to do one bike will cost around $20. By buying in bulk you can get that price way down and have the convenience of having stuff at hand.
What you need:
- shimano sp41 (XTR) shift cable outer - this is lightweight quality housing that comes pre-greased and is perfect for use with stainless steel 1.2mm gear cables. I got 10m in white for $17 delivered;
- stainless steel 1.2mm gear cables - 10 for $25 delivered;
- cable ferrules - $20 for 150 delivered;
- cable ends - $10 for 100 delivered;
How much/many of each of those items you need each time you replace your gear cables will depend on your bike. For my Anthem X I need about 1.2m of SP41 outer, 10 ferrules and 2 cable ends (as well as the 2 cables). This works out at about $8.50 for a complete cable change with high quality components. An XTR gear cable set will cost about $50, perhaps $25 on special. For an initial outlay of $70, you'll get enough supplies to do at least 5 complete gear cable replacements.
Also, I find that I replace my rear gear shifter cables about twice as often as my front shifter cable. The front shifter gets much less use and the greater cable pull when front shifting means that it is much less susceptible to not working properly when things get a little gummed up or dirty.