Jim’s Tech Talk
By Jim Langley
RoadBikeRider reader Bob AtLee asked this great question,
“Yesterday, after a month or so of sluggish shifting on my rear derailleur (Shimano 105 brake / shifter with an Ultegra derailleur) I finally peeled back the rubber hood on the brifter and lo and behold, there was the tangled mess of an almost-snapped inner cable, where the cable bends to go around a white plastic guide. My guess is it’s a couple years old, maybe 10,000 km on it. Being an old fart I shift a lot.
I’ve seen this before when my daughter’s cable actually severed, resulting in a complete loss of shifting on the rear and a ride finished on two speeds (the front derailleur only). Thank heavens we had come down to the flat country from a very mountainous ride (Icefields Parkway, Canadian Rockies). It took us a couple hours and some fine work with a dental pick to extract the moulded cable end from the shifter mechanism.
Is this endemic to the “new,” concealed cable style Shimano shifters? It sure – as – heck looks to me like they are asking for trouble, pulling that cable around a tight corner on nothing more than a Teflon guide.
Is there something a person can do to extend the life of the inner cable? Or is it a case of, well, one more thing for the annual winter service is to replace the index cable inners?”
I’ve seen enough STI shift cable failures inside the lever similar to what you’ve suffered, Bob, that I do think you’re correct and it’s a fairly common issue for people. But, I can’t remember ever having one of mine fail.
My friend Leo brought his bike to me to fix his broken cable and when I looked inside the lever I found the frayed mess but when I finally got the stuck cable head out, the lever still wouldn’t operate properly. I looked again inside the lever – but this time with a flashlight. And I was surprised to see another cable head wedged in there preventing the lever from working.
Apparently a previous mechanic had managed to replace the broken cable and had let the old cable head fall into the lever. Once I got that one out, and fed the new cable in, Leo’s shifting was good as new. I asked Leo about his broken cables and he said he was using inexpensive replacements, not Shimano’s. (But, I assume his Trek came new with Shimano cables so I can’t explain how the first one broke.)
Is It The Tight Bends In The Cable Path?
It’s tempting to blame the cable breakage problem on the design of the cable path in the lever. As far as I can tell, cables break on all the different models of Shimano STI shifters, not just the 105. And from the different models and different years STI has been on bikes the cable path has changed.
Could It Be A Bad Installation Or Cable?
I think there’s more to these cable breakages. For example, it’s fairly easy when installing STI levers, cables and housings to end up with gaps between the end of the housing and the pocket in the lever it’s supposed to sit in.
It’s also common for the cable housing to compress over the miles, which lets the wire housing liner protrude from the end. Both these issues could leave the inner cable unsupported and might lead to a cable breaking.
Another issue is the cable type and installation. Shimano recommends only using their cables and housings. On setups that require it, there should be ferrules on the ends of the housings. Also, the cable heads that rest inside the lever should be lightly greased before installation.
When installing the cables and housings, I like to make sure that there is tension on the cable so that the cable head remains seated in its pocket inside the lever and that the housing end stays seated in the lever body, too. If there are ferrules, I check carefully to make sure they’re fully seated on the end of the housing and that they seat fully in the lever.
Should You Replace Shift Cables Yearly?
I would hope you’d get more than a year out of your shift cables, Bob. It can’t hurt to look inside the lever to see if all’s well. But, I wouldn’t replace cables unless there were signs it was needed, such as fraying, housing issues, maybe corrosion.
I don’t know if this is true, but one of Shimano’s stated reasons for “upgrading” all its high-end road groups to their Di2 electric shifting is because it solves all the problems with their STI shifting. They don’t say if broken cables inside the lever was one of those problems. But, it wouldn’t surprise me if it made the list.
I hope something here is helpful and you don’t have any more STI cables break. Thanks for the great question!
Readers, it would be interesting and helpful to hear if you’ve had issues with STI cables breaking inside the lever and what you’ve done about it if anything. And please share your theories about why they broke.
Jim Langley is RBR’s Technical Editor. He has been a pro mechanic and cycling writer for more than 40 years. He’s the author of Your Home Bicycle Workshop in the RBR eBookstore. Check out his “cycling aficionado” website at http://www.jimlangley.net, his Q&A blog and updates at Twitter. Jim’s cycling streak ended in February 2022 with a total of 10,269 consecutive daily rides (28 years, 1 month and 11 days of never missing a ride). Click to read Jim’s full bio.
I’ve had this happen to me as well, but luckily it was in the winter when the bike was on the trainer. At the time my bike had 105 5500 9 speed shifters. When the break happened, the shift cable was about 4-5 years old and I was riding about 3 to 4 days a week. I suspect the tight radius near the shifter head is the blame- the cable at that end goes through a torturous path. My solution- change cables and housings every 3 to 4 years regardless. I don’t think there is much else you can do.
Chris VandenBossche says
My 2002 era Shimano Ultregra shifters were prone to breakage and the mechanic at my LBS told me it was a common issue at least on that generation. I used to replace them annually as a preventative measure. I also had it occur on my newer (2011) bike with Ultegra. I now have etap and no more shifter cables to deal with.
Bill Brannon says
I change the STI rear cable at 2,500 miles. They usually fail at around 3,000. A sure sign that it is starting to fail is when shifitng to a smaller sprocket starts to become hesitant. Freyed ends are catching and resisting the strength of the return spring in the derailleur. Easy to replace before it breaks. This failure behavior has been consistant since the very first Dura Ace STI launch. Change the front on every third rear.
Marc Wilson says
I replace my rear derailleur cable 2,500-3,000 miles and the front cable at 2x that. It’s a cheap fix to put the worry of a busted cable during a ride out of my head. Been doing this for years.
You might think of switching to Campy!!!
Seth H. Shaw says
It can happen to brake cables as well even with Di2 shifters, as it did for me a month ago. Removing the unraveled rear brake cable inside the shifter was so much fun, says I, tongue in cheek. The circuitous and compressed path of installing the cable from the shifter to inside the handlebar, back outside down the head tube, to snaking it inside the top tube, and finally outside to the brake, can’t be good for cable life. I love the clean look of internal cabling, but I see the downsides beyond the pain of installation.
Richard Handler says
I think it’s the added friction of concealed cables. Have had this issue with both Shimano and Force, but never, with either brand, when the same modern high end components are installed on my old Litespeed with external routing.
Nor does regular cable replacement guarantee reliability. Have had a new cable break at 800 miles.
My issue was always FD cables. Broken cables were the most common mechanical on the group rides and tours I’ve led.
Electric shifting solves the problem.
I’m with Glenn: switch to Campagnolo.!!
I’ve had the same cables on some bikes for well over 15,000 kms.! and still shifting great. Needless to say that none of my Campy bits have any of the engineering flaws mentioned here, and they all work faultlessly because they are always so well conceived to begin with.. And, when it’s time, they can be rebuilt easily and cheaply; no need to buy a whole new set. I don’t understand why anyone suffers through continued use of Shimano crap when there are such beautifully made components from the original ‘inventor’ of these mechanical marvels.
In the past 30 years I have replaced broken (frayed at the head) on all of Shimano’s STI controls, and Campy, and a couple SRAM’s doubletap. In my experience it was Shimano’s 9-speed that was most prone to it, and the hardest to fish out, although the plastic socket in the SRAM system was difficult too. What’s weird too is that it seems to happen in batches… I can go a couple years without fixing one, and then recently I had to fix 3 or 4 in one week, all of which had been ridden for a few years. I have a couple customers for whom I profilactically change the cables at least once each year.
Note too these later generations of Shimano’s 10 & 11-speed systems have trap-doors on the bottom of the STI body, held in place with little screws. These are easily removed, making it MUCH easier to extract a frayed and severed cable head.
PHILIP APRUZZESE says
The cable head extraction is much easier (and the cable end is lubed for a long time) if you add a few drops of Boeshield T-9 to the last couple inches when installing inner cable.
Paul Ahart says
For years I”ve recommended annual shift cable replacement to many of my customers. STI shifter cables are “out of sight-out of mind,’ kind of like motor vehicle maintenance like oil changes. Many people are oblivious.
Jim’s suggestions of lubing the cable knob end and cable, and checking to make sure the cable housing doesn’t have protruding wire strands, and that there are solid ferrules on the housing ends, all this is very helpful. Aslo important is making sure the new cable is properly seated in the shifter. If its not, the barrel end can get jammed in the lever, get damaged, and very difficult to remove and reinstall.
Replacing a shift cable while it’s still intact is quick and easy; if broken it can be a frustrating and time-consuming job. Consider annual cable replacement like an “oil change” for your bike.
Dave Cardarella says
I have a 2009 CoMootion tandem with Ultegra components. The rear shift cable breaks every 2500 to 3000 miles. The bike has 82k miles on it. Over the years I have replaced the shifter and derailleur several times. I just attribute the failures to the design. A tandem requires a 3 meter rear shift cable and most shops don’t stock them. I always carry a spare cable and can change it on the side of the road in less than 10 minutes. I finally got smart and started replacing the cable every 2500 miles.
I’ve had it happen 2 times, once with a Dura Ace shifter and once with an Ultegra. I now definitely replace the cables every 10,000 miles (once a year). It is just too much hassle although the newer Ultegra shifter had an access cover to get at the broken cable more easily than the older Dura Ace. I will have to say that Shimano was great and (this was 7-8 years ago) sent me a new replacement shifter because we couldn’t get the broken cable head out. They did that they said because I used all Shimano parts. On the Ultegra shifter, no such luck with Shimano, but that was fine since I was able to remove it anyway.
R Carey says
Happened to me this past summer – cable broke completely while literally 200 miles from home A few miles earlier I was shifted rather wildly as I navigated a series of steep inclines and declines.
In retrospect, I believe I had warning signs over the few months before. Shifting among the low gears became inconsistent and some rattling due to the derailuer not aligned well in the low gears. …so I’ll pay attention to those signals next time. BTW, I did learn a valuable hack – how to tie the cable so that the rear derailleur fixes the chain around a middle gear instead of the smallest.
David Coxhead says
This is an issue I have come across in our shop. Mainly Shimano but also seen on Sram. I have started to replace the cables with a more flexible braided cable. In the last 2 years I have not yet had any come back with the same problem
Jim Langley says
Thanks for all the interesting and helpful comments readers, great information!
David Zipf says
Campy cables are no t immune to breakage. I have had to cables shred and the broken wires poked my fingers. The key is yearly replacement
The cables get frayed inside my right (rear) Ultegra derailleur shift lever every 1500 to 2000 miles. I have had it snap on me twice, leaving me stranded and having to call for a ride home. I have since come to recognize the symptoms in advance of it snapping. If you find yourself having to adjust the cable length frequently, the cable is likely beginning to go. Sometime you can even feel when one of the strands goes.
I only use the highest quality Shimano Dura-Ace cables, but even so, need to swap the cable every 1500 miles. I recently replaced the $5 plastic cable guide under the bottom bracket on my Trek Domane, and this had a dramatic effect. The bike is now shifting like new, whereas before, it took a lot of force on the lever to shift. Apparently this cable guide was worn by the cables, and there was lots of resistance.
I’ve experienced this with Dura-Ace 7900 and 9000 shifters. In one case, the cable snapped, leaving a badly frayed head in the shifter. Removing it befuddled even the most experienced mechanic at my local shop. The only real solution I’ve found is to replace the cable as soon as there is noticeable deterioration in shifting accuracy. Consistently sluggish shifting that can’t be fixed by adjusting cable tension has for me almost always been an indication that the cable has begun to fray near the head.
John Klever says
When I had STI, may cables lasted 10 to 15,000 miles. I switched to bar ends. Problem solved. As the cable frays, my fingers are stuck by the broken strands, and it,s time to replace. I also don’t have to replace handlebar tape.
I’ve had the breakage happen for my rear derailleur inner shift cable 3 times so far — about 3000 miles between each breakage. It’s for my Shimano 105 5800 series shifters. I’m going to try using Shimano’s top-of-the-line polymer coated cables and possibly some of their cable grease to see if it makes a difference.