I had this problem, RST bike is 14months old, 4000miles, commuting, tour and audax use. I went back to Thorn and would recommend anyone to do the same, i sent a photo and a description, here is the reply:
Thanks for your quick reply.
I wasn't so worried about the corrosion, I doubt that the plastic liners would have broken, it was more how much of a struggle you'd have had getting the inners back through the new cable after they'd been removed from the grub screw secured clips. Presumably you cut them slightly shorter.
Generally, as with the replacement we sent you we use brake outer, not gear, this is because allthough it can start to fail as your's did, it doesn't give up all of a sudden, the gear outer, which has longditinal wire strands instead of spiral wound, has the following benefits:
1) Sharper feel to the gear shift
But the following bad points
1) 2 stiff outer cables facing the same direction put a bias on the bars to one side
2) when the outer fails it becomes useless as opposed to gradually
progressivly worse.
It could be argued that for an expedition bike (say the Tour) that brake outer should be used, but for a performance bike (relatively) such as the sport tour, gear outer may be a better a choice.
As to the difference in durability between the 3 types of outer we could use:
Taiwanese cable by Jagwire
Singapore cable by Shimano
German cable by Rohloff
We've no collated data, except to say that we actually DISCARD the Rohloff cable outers that come with the hubs because we've found that the plastic liners are not bonded to the outer and can become detatched and pull into the shifter causing it to jam!!
Regards
Robin Thorn
In another email the problem was acknowledged without dispute. The high level of customer service i have received from Thorn in general, was no less evident in their dealings with me over this issue.
The heatshrink solution is novel, but ultimately, cables and outers are consumables.
