Chafing gear cables
My cable that failed was from a bar-end control that didn’t emerge from under the bar tape until some way around the first curve, so it bent upwards a bit before curling back. That caused the cables to rub gently on the bottom of a bar bag. I thought nothing of this, as it didn’t seem to be hurting the Ortlieb fabric, until the front mech wouldn’t shift up…
A flat spot had worn on the hard plastic that covers the lengthways wires that give indexed gear cable casing its resistance to compression. This plastic coating binds those wires together. When this plastic case is critically weakened, the wires can buckle under compressive force (that’s equal and opposite to the rise in cable tension when you shift) and burst apart.
Having jury-rigged my front mech in middle ring, I wound insulating tape around the other casing, which I now noticed was also worn to the wires!
STI cables rubbing on the sides of a bag will surely suffer the same fate – and maybe sooner. A good precaution is to apply the binding of PVC tape before any wear occurs at all, as it will become tatty before the casing wears. Preferably route gear cables where they cannot rub.
For STIs with ingrowing ‘washing line’ cables, consider Nokon casings (distributed by windwave.co.uk and pictured below). Their jointed metal outer sections are resistant to chafing and allow tighter curves, which should enable you to keep these casings clear of the bag. This you will need to do, or else they’ll surely chafe the bag instead!
This was first published in the February / March 2014 edition of Cycle magazine.