8/5/15 8:35 PM

My rear derailleur cable broke! Fortunately only a few miles from the car at the end of my ride. And those remaining rides were mostly downhill. So I was able to use the front rings, turning my 27 speed drive train into a 3 speed one. Make it back without missing a beat.

But, this was the second broken derailleur cable (in 5 years).

I've been lucky. The previous broken derailleur happened in the middle of a village that has a high end bike shop. So they replaced my cable on the spot. Very lucky indeed, for I was a good 20 miles from home, on rather hilly terrain.

Looking closely at the broken end (near the bolt), the broken end was frayed. I wonder if I could have spotted the fraying BEFORE it actually broke? Had I been looking closely, that is.

I know some advocate replacing cables every other year (or some other schedule). But seeing each rider rides vastly different mileage, I inherently dislike time-based replacement scheme.

As my bikes are both beyond 10 years. Bits and pieces of the original components are reaching their end of useful life, at different rate.

Do any of you "inspect" cables? Or wait when there's signs (poor shifting? mushy lever? what else?) before replacing cables?

8/5/15 9:01 PM

I keep a lot of extras. And periodically put bike on stand and do a quick go over. If I see an cable starting to fray, I just replace it. I do have the luxury of not using the same bike over and over and spread the wear across at least 2-3 bikes usually. But periodically can be sooner if I get a quirk on the road with shifts I can not adjust out on the road. Once I get home pop it on the stand and google it.

Seems like if it started popping strands right at the bolt, some over tightening was involved maybe, cutting into a few strands??

Was there a cable crimp on the tip of the cable, and was there at least 2" or so of length after the securing bolt?

8/5/15 10:03 PM

My inner cables tend to fray at the brifter end and it is hard to spot the fraying. I have two bikes the main bike is ridden about 3k miles per year and the older (bad weather) bike about 1.5k per year. I replace the shifter cables every 2 years on the main bike and about every 4 on the older bike. I always use OEM cables as they tend to be better quality for only slightly more money. In fact on a previous bike with Campy brifters the after market cables had a slightly larger ferrule and would seize up in the brifters.

Brake cables are another story. I just replaced the brake cables on the main bike after 15+ years. The inner cables looked like brand new and the only wear was cosmetic on the outer housing at the brake end. Again I used OEM Shimano cables and housing.

8/6/15 5:26 AM

The clamping bolt and nut can be fraying the cable also. Check that it does not cut into the cable strands.

I solder my cable ends and don't use the little crimp on things. I think this works much better and allows me to remove the cables for cleaning etc. Shops don't do this because it is a pain to solder the cables.

8/6/15 6:14 AM

I've had maybe 2 broken deraileur cables in 8 years, or so, but they were both with rear deraileur at the brifter end. I don't really recall the details of the earlier break, but the latest one happened last August and was preceded by a couple miles of wonky shifting where I was scratching my head as to what was going on. That time I was only about 3 miles downhill from home using a shortcut, so I just tied off the cable around the water bottle cage with the deraileur in the 19 cog, or so.

Other than a very brief visual once-over when the bike is in my workstand, I only tend to inspect the cables if I'm having issues with the shifting.

8/6/15 6:35 AM

Good topic. Newer Shimano stuff needs very regular cable replacement, especially on 9000/6800 stuff as the cables are thinner than previous to aid shifting. We've seen a rash of broken cables on our group rides, almost always at the brifter, and frequently the head drops into the mech and jams it up. Even if it doesn't extraction is difficult, even in the shop. I saw a pair of perfect 7800 DA levers essentially trashed by this two weeks ago.

I'd advise annual replacement of derailleur cables, even though it may seem like overkill to many.

8/6/15 11:01 AM

+1 on **annual** cable replacement, both shifter & brake cables. I never had cable issues as a result.

8/6/15 11:34 AM

I probably never go beyond a few seasons for shift cable changes and agree waiting for a head to drop into your expensive STI is a non starter.

8/6/15 4:38 PM

"Newer Shimano stuff needs very regular cable replacement, especially on 9000/6800 stuff as the cables are thinner than previous "

Hmmm... so there're different cable thickness for different brifters?

8/6/15 5:22 PM

Two classic signs of failing cables are:
- Inconsistent shifting
- Needing to adjust the cable tension repeatedly to center the rear derailleur over the cogs.

It's easy to ignore these signs or write them off as being caused by something else, but they're almost always present before a cable fails. The fact that you've had two unexpected cable failures means that you need to pay more attention to what's going on with your bike(s).

I don't know if I've ever had a front derailleur cable fail. They seem to last forever because they get so much less use than the rear.

8/6/15 6:54 PM

Yeah-when shimano went to 7900/6700 there was much teeth knashing about the increased shifter effort resulting from routing the cable under the tape. With the change to 9000/6800 Shimano went to a slightly thinner teflon coated cable to reduce friction and solve this. The teflon would wear off at the bend near the brifter exit, and the cable would fray there. Shimano addressed this somewhat with reducing the radius in the 9000 refresh.

So yeah, change 'em. Note that the trashed shifter to which I referred earlier was 7800- likely no change for a while, but it dropped the head into the innards.

Brian, its funny, all of the broken cables I've had have been fd, but it was always Campy.

8/6/15 7:45 PM

Both of my broken cables are rear, one Campy and one Shimano. Both lasted more than 2 years. So I'm inclined to think they've simply reached their natural life. I'm not unhappy about their lifespan.

As for poor shifting, yes, that was the case. But it only started a couple rides back. I did the logical thing first,, clean the drive train. Shifting improved considerably, but then deteriorated again. The last ride, the shifting got much worse within 20 miles. Then I broke the cable 3 miles from the car.

While cleaning the chain, I didn't notice any obvious issue with the cable. Granted, I wasn't specifically looking for cable issue at the time. Had the cable survived that last ride, I was going to check its movement to make sure there's no obstruction. But I was 3 miles too late on that!

8/6/15 8:18 PM

Better 3 miles than 20 to be sure....

8/7/15 12:03 AM

In all my years of riding I have only ever had 2 broken cables, both rear shift cables, both on the same day and on 2 different bikes. Thought I was cursed! They both broke at the brifter end so couldn't see it coming and hadn't been aware of degraded shift performance.
I have heard that the updated 9001 shifters had been modified/ released because of cable issues of premature wear on the 9000 series DA shifters, which is what mine are.

8/7/15 10:23 AM

Having tuned up a rather large number of derailer bikes, one thing I've come across makes me wonder why it isn't more well-known.

Seems that different "mechanics" have different takes on just how the sequence of derailer and cable adjustments should be performed!

If there is any force acting on the low-limit screw after the shift to the largest cog has been completed, that is force that adds greatly to the value of the maximum cyclic tension that the cable ever sees.
On older bikes with indexed down-tube shifters, a too-tight adjustment of the low-limit screw would manifest as a tendency for the bike to auto-shift to the next larger cog during the hardest climbing efforts, and was known to actually wear out the low-gear shift detent over time. The same force on the low-limit screw that causes this drastic, cyclic peak in cable tension will of course fluctuate with pedaling intensity and will fatigue the cable in relatively short order.

I always test the low-limit screw adjustment by verifying that a tug on the exposed cable run at least results in some minute movement of the rear derailer while in low gear, a guarantee of sorts that the cable tension isn't cyclically spiking to some astronomical force level, which would otherwise result in more-frequent loss of proper cable tension adjustment and thus indexing accuracy as well as shorten the fatigue life of the cable.

Properly adjusted, STI cabling can last a surprisingly long time.

Note also that re-adjustments of cable tension to compensate for a different wheel will of course always require the limit screw adjustment to be re-checked, also that heavy-handed shifts up to the largest cogs may push the derailer heavily against it's low-limit stop, spiking the cable tenson radically.

I think that a somewhat well-deserved paranoia of a possible chain-in-the-spokes incident allows some "mechanics" to ignore the need for adjusting the low-limit screw properly on indexed rear derailers.
And of course indexed front derailers also need to have the hi-limit screw backed off from pressing tight against the indexed high-gear position of the derailer, to prevent a similar cable over-tension condition.[/i]

Last edited by dddd on 8/8/15 2:38 AM; edited 2 times in total

8/7/15 11:56 AM

"If there is any force acting on the low-limit screw after the shift to the largest cog has been completed, that is force that adds greatly to the value of the maximum cyclic tension that the cable ever sees. "


Not the greatest thing for a STI innards either....

8/7/15 1:12 PM

My Rival shifter just blew up, 17000 kilometers, I won't complain. The cable is fine though. :)

8/7/15 2:12 PM

Reminds me that it is wise to detension cables when storing bikes-little chainring, little cog in rear.

8/7/15 2:36 PM

At static load there really is no wear on a cable. No need to detension for storage. Just as this does not "save" the springs on a derailleur or brake.

8/7/15 4:13 PM

I didn't realize cable management was this complicated! In 43 years of riding, I can't remember breaking a cable (which doesn't mean it hasn't happened). I never check them, and never replace them unless I change or overhaul the brake or shifter (rarely, I've had a typical g-spring replacement or 2); or an obvious problem comes to my attention (maybe 2 or 3 in that time).

I do spread my miles out over a number of bikes, and use Campy. As Campyman says, just sayin'. Even though I am fairly heavy, I seem to be easy on equipment (basically I never break anything).

8/12/15 7:26 AM

Seems to occur with increasing frequency for fellow riders. Never broken one myself although I replace my cables and housing every 2-3 years. When I remove my old cables I take a quick look and have not noticed any signs of pending failure.

While regularly replacing housing can be a hassle for some, replacing a cable is pretty simple and cheap to do yourself. Perhaps something you want to do on a schedule of some sort.

On our tandem I carry an extra cable because even if I found a shop on our route, finding a tandem length shift or brake cable would be a challenge, not to mention the fact that it is a Campy cable. Perhaps when you replace your cables coil up the old one if not damaged and stuff in your seatbag, just be sure the end does not fray.

Long ago I used to solder cable ends like Erik. For the last several years I have switched to superglue. Simply get a clean cut and then dip the cable end about an inch into the superglue tube a couple of times. Make sure a drop does not form on the end.

Have used the water bottle tie off trick that Lee suggested for other riders. They are simply amazed when it saves their ride.

8/12/15 10:44 AM

Fraying ends, Erik mentioned soldering them. I used to do that, now once cut where it frees the strands, I dip in acetone and then CA glue. Even removing the crimp and doing a DR housing loop replacement, cable does no fray. After inspection of the ball end by pushing out at least the length of the first housing, I use finish line on all sections of cable that reside in housing, let dry, and put back together.

I think if when in the biggest cog in the rear if the DR adjustment in fact stops the cable before the STI is done pulling this puts a lot of stress on the head. never had a compromise at the head of a cable personally, but I do all my own wrenching and do not allow that stress on STI and cable end. More worried about the STI, but two fold perhaps...

8/12/15 1:40 PM

I tried CA. It did not last due to the heat and humidity here. So I went back to soldering mine. It is still pretty quick.

8/12/15 3:15 PM

Notice I did not say crazy glue, although it is CA glue. I have stuff that will permanently fill and hold/stop a check/crack in a one piece wood solid body guitar body. Not had that stuff let go yet. Gorilla CA at Home Depot is probably the closest to this stuff...

8/13/15 9:17 AM

Does your CA* glue foam up like the Gorilla CA I've tried? That was years ago and I vowed to never use it again.

(*cyano-acrylate I guess)