genejockey 

Not completely broken, no. BUT.....

I just replaced the shift cables on my Canyon (R7000 105), at ~5000 miles (mostly IRL, but about 1/3 virtual). On the rear cable, 4 of the strands had broken near the cable end in the shifter. Shifting in the rear had gotten sloppy, in particular the chain took a second or more to drop to a smaller cog. Shifting to larger cogs sometimes seemed to need overshifting. When I replaced the cable, it shifted instantly again, in either direction. No overshifting, no hanging onto the larger cog.

This had happened gradually, so that I didn't notice the degradation. I did notice that the R8000 shifting on the Litespeed I'd just built up was a LOT crisper, but I put that down to it being the next level up. Now, with new cables, they're equally crisp. Silly me. Should have changed the cables earlier.

msu2001la

Exactly my point. The OP’s LBS said the shifter is *broken* and needs to be replaced. The second shop “adjusted” things and got the bike shifting but the OP reports continued problems.

The shifter (probably) isn’t *broken*, it just needs a new cable installed. Yes, it may be fraying.

I have no idea why photos of broken shifter cables are being posted in this thread or what that has to do with the OPs questions. No one is arguing that shifter cables never break.

Does a frayed cable result in a broken shifter? Seems unlikely but I guess it depends on how frayed?

Spandex_fairy

Update:

I got around to it, and you guys were correct. The cable was more than half-way frayed at the shifter. I decided to give the Dura-ace cables a go; just in case I get more life out of it. I had a heck of a time seating the head of the cable. It just didn't want to go in naturally. I had to tamp it in. I'm researching how to properly index the deraillure. It was indexed for the frayed cable. I fully closed the cable adjuster (clockwise) when installing the new cable. The bike would not shift until I unwound it a fair bit. This means I need to adjust the indexing. That's next on the list of things to learn.

spelger

me thinks that Kontact's point was that left alone the result would happen. and he is right.

spelger

if you had trouble getting the new cable back in then make sure there were no left behind wire bits in the shifter. once they begin to fray it is not much longer before they just break off completely and little bits are left in the shifter even after getting the cable out. if you had to tamp down the ball end to get it to seat properly then chances are that there may be a bit of wire left behind.

genejockey 

Oh! That's very different then.

Kontact

You said the cable wasn't broken. It was half broken. No one here said the shifter was broken. I said that broken cables can kill shifters because they can permanently jam the mechanism. Not unlikely - unfortunately common. So common that I decided to make the point by posting pictures to illustrate.


To reiterate - the OPs symptoms were so incredibly familiar that I got the cause on the first guess. Shimano shifters eat cables. Keep your bike clear of problems by replacing the cables each season.

mschwett 

at 5,000 miles my GRX RD started requiring two shifts (and then one back) to go one cog bigger. shop replaced the cable and adjusted, back to new performance. they knew instantly what it was - this seems like a VERY common problem. sorta makes me wonder if 105 going di2 is their way of saying “we don’t want to deal with this any more!”

Maelochs

A rare BF thread with a happy ending.

The bit about Shimano going electronic to avoid further cable issues struck me as humorous .... but it also raises points worth considering.

Because the shifting is done with a rotating motion with the axis aligned with the frame's main tubes, and the cable runs along the same axis ... and the cable pulls at 90 degrees from that axis ... and because people want under-tape cabling .... and because 'lighter and more aero" is such a big deal .... Shimano is stuck. They would have to completely redesign their brifters, maybe add a bearing and guide on the side to smooth the path of the cable .... added weight, added complexity, added width ....

Maybe Shimano really has figured "Brifters are about as good as they are going to get so let's just accept the faults and introduce a new system." No cables, no cable issues.

In any case .... glad @Spandex_fairy got on top of the problem before disaster happened. Broken cables don't Always mean broken brifters, but with the comparative costs ..... Plus once he watches a few videos, he will be indexing his own stuff. bravo!

I suggest watching a few different videos, because each will have a slightly different approach, but I rely on Park Tools for a lot of bike wrenching instruction.

Kontact

Shimano did completely redesign their shifters. Remember how the shift cable used to be external? Campy has been making brifters almost as long, and Sram has for well over a decade, and neither have a cable breakage rep. Shimano downtube, thumb, bar end and MTB STI also don't break cables. I dunno why Shimano keeps screwing this design element up when it clearly isn't that hard to get right.