Is there any way to check if shift cables are about to break?

I have a Shimano 105 mechanical groupset and I would like to know if there is any way I can check if my shift cables aren’t frayed or about to break? These cables often get frayed when I am out on a ride and I have to complete the ride while being stuck in one gear.

Whenever they have went on me or a friend’s bike the always go right inside the hood. It last happened with a hire bike in Spain and the owner swears that the cable was less than a month old. The only warning sign IMO is that shifting may get a bit slow and sloppy.

Edit: oh and I was stuck in two gears (a 2x front) and adjusted the limit screws so it wasn’t the highest gear I was stuck in.

The most common place to fray is the shifter, where they are repeatedly wound and unwound with each move through the gear range. Unfortunately, this makes it difficult to see. And because it is so slow and gradual to degrade, it is difficult to go by feel as well. One tell tale sign is while they will shift onto a larger sprocket smoothly, they are slower to shift onto a smaller sprocket . The reason for this is that shifting onto a larger sprocket happens when you pull on the system with the shifter lever and you can always apply more force, but shifting onto the smaller sprocket occurs as you release the cable, and the shift happens only under the tension of the return spring in the RD. This is the point where increased friction in the system is likely to show up.

Shift cables should be replaced once they START fraying, not at the point where they are likely to break. Trust me, performing surgery on your shifters to retreive broken bits of cable is something you only want to do once in your life.

And if your cables had frayed/broken, it is probably time you replaced the external housing as well - fraying cable can eat away at the housing lining, bits of lining can move through the system, further abrading the housing lining, and increasing friction all the way through.

Personally, I got into the habit of replacing my shift cables as a preventative measure about every 4000 miles, and replacing the external housing every 3rd time I replaced the inner. Shifting remained smooth throughout, and it is much easier to replace an unfrayed cable than one that has begun to fray.

4 Likes

Yes - roll back the hoods - on the outside of each shifter you’ll see a little plastic panel that can be flicked open - this is where you would feed in a replacement shifter cable. Grab a torch - flip that open, then shift from the smallest to the largest sprocket - you’ll be able to see the portion of the cable most exposed to bending and fraying being pulled through that area. If it’s not shiny and new looking…replace.

1 Like

Also, whenever I have the shifters off the bike - as you’ll likely be replacing the bar tape too, why not? - of flushing them out with degreaser and really hot water,

1 Like

Really helpful, thanks!

@mcalista Previously I used to wait until my cable got pretty frayed. I remember one day when I was at the bike shop and was told that the labor cost to remove bits and pieces of the frayed cable from the shifter is more than the cost of the shifter itself! Fortunately, the mechanic was able to remove it pretty quickly. Definitely don’t want to go through that again.

@Dogfather I don’t get it as to why I need to replace the bar tape? The bike I have is only slightly more than a year old with most of the riding done indoors. I don’t take off the shifters when replacing the cable as I only need to peel back the hood.

Usually the advice is to replace the outer cable housing at the same time as the cable, and usually the cable housing is under the bar tape, so in that case, you likely have to replace the bar tape too (unless it is a type that doesn’t stick and can be wrapped over again). (Maybe not true anymore with integrated bars?)
However, if the cable is still in good condition, not frayed or rusted, you might be ok to just replace it, and leave the outer alone.

Wow, mime pretty much all start to break by 3000, miles, enough so that i change mine at 2700 miles. Not sure what im doing wrong or your doing right to get 4000 miles per cable. Fun fact, Back in the early 2000s, with 10 speed dura ace, id get over 10,000 miles per cable, not sure if the cables are weaker or the new shifter design causes them to fail, but i miss the old days.

It’s going to be highly dependent on how often you shift. I wouldn’t be surprised if cyclist riding in very flat and smooth areas get much longer life out of the cables versus those that encounter a lot of short steep climbs.

2 Likes

I think it’s due to the tight bend the cable has to perform inside the shifter now before it routes out the back, whereas before it was just straight out.

I’m riding my son’s bike at the moment while mine is off to the painter…ultegra 6600, the last of the exposed cables - the shifting is still so light and positive. I was thinking the other day on how many generations of Ultegra I’d ridden - all the way back to 6 speed 600 with the first SIS downtube cables.

There haven’t been a lot of duffers in there. 6700 was I think the worst by a country mile, those first hidden cable shifters could be pretty much guaranteed to let me down at the worst possible moment. 9 speed 6500 - that was ok, but got really sensitive and skippy as chains and cassettes wore. I’ve found 6800 to be pretty near faultless, bar the front shifter. Chucked a 9000 in it’s place and I’m at 50k troublefree k’s.

Just picked up 8000 while it’s about, more just to complete the set of mechanical rim brake Ultegras. Looking forward to it!

On outer cables - I usually totally disassemble and service my bike every winter, replace these annually. Inner cables, maybe every six months…