spilot101

ibb.co/qxcnjST
... snap, by the looks of it. Any idea as to what might have caused that?

JohnDThompson 

Pic assist:



Looks like the cable wore where it exits the barrel adjuster. It hard to see if this could have been prevented. The angle at which the cable enters the barrel adjuster doesn't align with the anchor bolt.

Replace ASAP, or get used to pedaling in a high gear.

Litespud

clear cause. How old is it? My rear shifter cable does this maybe every year, fraying at the shifter. Fortunately it lets me know, as errant strands start sticking in my fingers

dsbrantjr

You might want to make certain that the barrel adjuster and exit hole on the derailleur do not have any burrs or sharp edges, perhaps put a radius on the corners with a file.

rhenning

The only question I have is why is the cable rubbing on the rear derailleur bolt. Roger

cxwrench

Rubbing on the bolt? What are you talking about? Where is the cable rubbing on a bolt? These derailleurs chew through cables quicker than most, but the OP is missing the little tube that should be sticking out of the derailleur. The cable runs through it on the way to the anchor bolt. That helps a little.

Shimagnolo

Every time I've replaced a shifter cable, it was always due to fraying inside the shifter, but never at the derailleur.

rhenning

The socket head Allen bolt on the derailleur shows a bend in the cable at that point. Why is it bent there? Roger

KCT1986

Can you tell us the model number of the RD please.

sincos

Looks like the clamp to me.
As for the fraying, maybe a radiusing insert fell out?

KCT1986

Was wondering the same thing. On the older RDs, there was a ring press-fitted on the exit side of the cable hole, opposite of the cable tension adjuster. This would sometimes get pushed out by fully screwing in the adjuster.

The newer RD have a different design that has an insert that goes in from the tension adjuster side. Haven't examined how this looks or how the cable is effected by this new design.

Thus my earlier request for RD model #.

dedhed

I see it going into a slot as intended.

Russ Roth

Someone just pushed it out of the way.


Does seem like a poor angle for the cable to come out at, not surprised it frayed. Just replace and move on but do check the barrel adjuster for burrs that could have done this.

spilot101

Thank you all!

About a year old, only 4,000km on this bike

​​​​​​Shimano Tiagra 4700 GS

reconnaissance

You can see that the cable makes a bit of a bend as it exits the adjusting barrel, and is probably rubbing on the inside edge where it enters open space. This combination of flexure and friction is fraying the cable a strand at a time.

This appears to be a design flaw in the derailleur.

cxwrench

That's normal.

There is no 'radiusing insert' but there is this:
Part # Y5XX38000 'Cover with tongue' It's designed to prevent this from happening...for a while. Just like in the shifter it will happen eventually.

spilot101

Awesome, thanks. Just dropped the bike off and let the mechanic know about that part

KCT1986

That part may not be present in the RD-4700. The diagram posted is of a different model, it's for a Dura Ace.

Attached is a pic of the RD-4700, note the pressed-in insert on the exit point of the cable housing stop. This was how older RDs were designed. The "cover with tongue" is new and included only on newer higher end RD. Not sure if these designs are compatible.

spilot101

Back in business.

DorkDisk

Stock up on road shift cables, the new Shimano road stuff eats them up.

canklecat

Yeah, with some systems, plan on replacing shifter cables at least once a year, maybe more often. Some brake cables seem to last forever -- my early 1990s Univega is still on the original massively thick brake cables. But it's gone through shifter cables about once a year. Ditto my 1980s-2000s road bikes, although I replace brake cables once a year on those as well.

TiHabanero

Replaced the rear der cable on a SRAM Apex bike this past Tuesday. It was fraying exactly as the one in the picture, however it was about 5 years old. I see this every once in a while and am unable to figure out the exact cause. I have even seen it on der with the extended sleeve as shown in the second pic. Just may be one of those unsolved mysteries of the universe.

djb

spilot, my suggestion is to start to try doing some of your own bike mechanical work, so many advantages, but if that's not your thing, it's not your thing.

it's like anything, it's a gradual process learning new things all the time

spilot101

I'm working overseas at the moment, so it's a bit of a "benefit-cost" analysis situation at the moment, as I would need to throw all of my possessions away before moving back.... With that said, I've gotten a stand and a couple of toolboxes to deal with cassettes, rings, bb etc. Looks like cables are more expandable that I'd previously imagined, so this might need to be my next YouTube lesson.

djb

It's also a gradual process of aquiring tools, and at some point, a good quality cable and housing cutter is worth it, will be paid for in not too long doing things on your own.
again though, only if you're into it.