If you’ve been having issues with shifting, especially on the rear cassette, you may want to look outside the box before fiddling with the adjustment knobs. There are 3 key things that almost always cause rear shifting to degrade:
- Cable friction: Check that the cables are in good condition and move freely within their casing. This is easy on a bike with exposed cables, not so easy on a bike with internal cabling, but probably more likely to occur on the former anyway.Get the bike on a stationary trainer or turn it upside down. Change to a low gear and check that gears line up, they probably do. Then, change to the highest gear and see what happens. If it does not engage fully, try moving the rear derailleur cage so that it does.
If this is possible you may have internal friction on the cables. If so, shift to the lowest gear, run chain oil along the exposed cables and shift to the highest gear and back a few times. If that doesn’t work, replace the cables.
- The chain is past its use by date – This usually shows when the chain does not shift properly into lightly used gears, and/or the smaller cogs. Check the chain with a chain measurement tool. This is the easiest and most reliable way, any tool will do, though I am a fan of the Park CC-3 as it gives an indication of wear compared to a simple go/no go approach.
There are other ways to check the chain but they require more time, or are not as effective or accurate. A chain checking tool is often cheaper than the price of a new chain.
The chain should be replaced frequently as if it is not replaced, the wear will accelerate on the cassette and chainrings, which in some bikes can cost more than the price of 10 chains put together. For the record, I only get about 1,500km out of a chain before replacement.
- Check rear derailleur alignment – this can be done with the naked eye checking the inside of the cage is parallel to the midline of the wheel or hub, and that the chain holds a straight line when going through the derailleur to the gears.
However, the one that always seems to crop up most often is option (2). With frequent use in good weather with no crashes it’s pretty unusual for the other two to happen. Well, less usual that chain wear is likely to happen anyway. Most often it will creep up until one day you’ll be wondering why you can’t shift into the highest gears, and that’s the time to check your chain, hopefully it’s not too late.