When Shimano dedicated itself to index-only, ratcheted shifting in 1990, it ushered in a whole new era of problems in bike maintenance and repair. Not even they knew what all could go wrong. It was also the beginning of a more predatory relationship with customers. As technology proliferated through the 1990s, customers became test pilots for complicated mechanisms being rushed to market to secure a competitive sales advantage while consumers were spending indiscriminately. The industry focused its efforts on redirecting the surge of enthusiasm for riding into a surge of enthusiasm for buying things.
Some changes really are improvements, but did we really need "model years" like cars? Hell no. Lots of people would have been happy to buy bikes that looked the same from year to year and were equipped with simple componentry that performed reliably. But as soon as "Rapidfire" was introduced, the concept had to be refined to replace its initial flaws with newer, flashier ones.
Shimano warned us from the beginning to stay out of the mysterious interior of their magical devices. "You can't fix anything in there, so don't even try." At the time, one of the bike mags had a snippet about a couple of intrepid mechanics who disassembled brand new Rapidfire shifters and reassembled them exactly as they came apart, and the shifters failed to work. This implied that we wrench-monkeys couldn't handle the precision mechanism of tiny parts in perfect synchronization inside those sophisticated shifter pods. Having peeked under the hood, we could believe it. "If it quits working, replace it," said Shimano. Now I wonder if the article was disinformation to discourage exploration.
Years later, out of necessity, we discovered that the most common reason for a Rapidfire shifter to fail is congealed factory grease. Ralph dubbed it earwax because that's what it looked and acted like. Clean out the earwax and most non-functioning Rapidfire shifters of any generation start to work again. You have to be careful to follow up with a light but persistent oil to keep the mechanism from freezing up later either from residual grease drying out or from micro-corrosion because all of those tiny levers and springs are no longer protected by the original petroleum product. Fun fact: before Shimano factory grease turns to earwax it looks a lot like pus.
When the road version hit the scene, it integrated the shifting into the brake levers. Other manufacturers had to follow suit. Asian componentry had always had an edge because it usually cost less -- sometimes a lot less -- than the top European stuff, notably the coveted Campagnolo. Campy's Ergopower shifters had better ergonomics than Shimano, by keeping the brake lever as a brake lever, and using a thumb lever for the upshift. Campy was also completely serviceable. Many parts transferred from one model year to the next. But it's pricey, and other aspects of the gruppo might guide a rider to choose Shimano. Because corporate warfare was in full swing, you had to commit to the whole package. There was little that you could mix and match. Riders suffer so that corporate coffers can benefit. The world becomes a worse place because the parties in power focus on their power rather than promoting the general welfare and ensuring domestic tranquility.
Shimano road brifters get earwax, the same as their country cousins on mountain bikes. They also suffered from another, more frequently fatal flaw: Strands of Death.
Inside a road brifter, the cable has to turn around a tight radius to travel enough to haul the rear derailleur across eight, then nine, then ten, and now 11 and 12 cogs spanning an ever wider range of diameters. The mountain shifter sits parallel to the handlebar. The pod can grow a bit to accommodate a larger wheel around which the cable is pulled. I have never seen a shift cable blow up inside a mountain shifter. But I see it all the time in Shimano road brifters. Because the shifting mechanism sticks out perpendicular to the bar, the diameter has to stay within a reasonable size to fit into a brake hood. You may have noticed how road lever bodies have gotten progressively fatter over the years. This is only partly to provide a more comfortable grip over the long road miles. That's a good cover story for the need to make more room in there for all the little ratchety bits. Even with that, the drum that the cable rides around torques the cable down pretty hard over a small area, fatiguing it in a matter of months to the point of failure.
Actual time to cable failure depends on use hours, of course. Other variables include cable quality, housing drag, gear range, and riding environment. You might go a couple of years. Conversely, if you're training a lot and racing frequently you will stress the cable more quickly.
Because Shimano's STI road units could not be opened, cable failure frequently jammed the mechanism completely. Cables don't break when you're in top gear where the head of the cable lines up conveniently with the hole through which you install and remove it. They break when you're jamming desperately on a shift to low gear under load. Maximum tension, maximum windup: blam. The cable usually blossoms instantly into a bouquet of fishhooks.
Failure usually takes a while. Riders will report that the indexing has gotten unreliable, and maybe the shifter feels crunchy. But the problem can progress rapidly, from early mild symptoms to shifter-jamming catastrophe in a single ride.
Because we had to work blind in many models, digging out the fragments could take a lot of time and fail to get every piece. Then the rider would have a ghost in there, like that floating piece of cartilage in your trick knee, that floats into a bad position and then out again.
When the shift cables came off the outer end of the brifter, the housing was fully exposed and could in most cases be released from its stops without undoing the cable from the anchor bolt on the rear derailleur. Then you could check the cable for failing strands by poking the liberated bit of slack out the other side of the brifter. Once Shimano routed the shift cables under the bar tape that became impossible. But they did start putting little access hatches into the lever bodies so that broken cables would be easier to dig out. As with many of their remedial actions, they did not call attention to the improvement, probably because they did not want to acknowledge any responsibility for the prior problem.
On Saturday, a rider came in with her Trek gravel bike, complaining that she could "only get about two gears." The bike has hydraulic disc brakes, so it has brifters that have a master cylinder taking up a lot of space in the lever body. The shifting mechanism is pushed way out front, from which the cable has to travel a couple of inches just to get to the cable housing under the bar tape.
The problem clearly went all the way through the shifter.
The head of the cable was all the way down at the bottom of the slot, far from the exit hole.
We were now at the mercy of the designer of this technological marvel. I saw some fasteners: the usual tiny Phillips head screws, and a couple of aluminum Torx nuts that turned out to be T9.39857, smaller than T10, but a sloppy fit for T9. And the heads were annoyingly shallow, making it hard to keep the tool in there securely. But at least I could take the covers off to get at the mess.