Originally Posted by
JohnDThompson
They even fail on external-drum, downtube-mounted shift levers. But in that case, the impending failure is readily visible to the rider (and individual failed strands alert the rider by poking into their fingers when shifting gears). Drum diameter is inversely proportional to cable failure; the larger the drum, the less likely it is to precipitate failure. Perhaps those MTB and non-Shimano shifters use larger drums than Shimano?
I have seen a tremendous number of shifters, and cable failure at the drum is not something I would consider a feature. I would not say the road STI drum is as small as most friction levers - but they do get used more often. But so do MTB STI.
I think there is something more specific to the Shimano design contributing. And it might be the low tension on the cable because Shimano uses soft derailleur return spings, so the cables are breaking like low tension spokes do.