Shimano Shadow + XTR - chronic gear cable snapping

[Rhys_]

Who else has this problem?

To me it appears to be a design flaw, where the cable routing just before the clamp allows the cable to rub against the sharpish edge of the cable groove in the mech. However the problem doesn't seem particularly widespread based on a quick google search, which is a little weird given how many of the these derailleurs there would be around.

I've basically never snapped a gear cable in my life until this mech came along, now I've been through two in about 10 rides. Current plan is file off any sharp edges I can get at along the cable path, and start carrying spare cable. Thoughts?

 

[sedifus]

I found I had some trouble like this on my SRAM x9 type 2 mech.

I was in whistler for about 5 weeks and went through as many cables. To be fair I was doing long rough runs and beating the bike but I thought it was unusual. Tried different cable brands etc and couldn't fix it. I assume it was a combo of the tight tension in the chain from the clutch as well as chain growth and a bit of friction and rubbing (would always snap where the cable meet the actuation arm on the derailleur).

I never got around to fixing it. Broke my hand and came back so never got around to trying any real fixes but this is what I had some ideas:

Less clutch tension
Higher end cables (shimano and SRAM both do fancier cables)
Some sort of sheath on the part of the cable around the lip, maybe some thin electrical wire casing etc
Or a washer under the cable clamp and bending it to have a curved edge instead of lip.

Not sure if the last 2 will affect shifting...

If nothing else works you can get them really cheap in bulk

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[teK--]

Post a photo.

 

[Rhys_]

Thanks sedifus, some really good thoughts there. My chain is as short as I can get away with, and my clutch adjustment is maxed. Neither of these I really want to change.

The last cable I used was a random I found in the shed, brand new and very thick (could have almost been brake cable). It managed to get through that as well unfortunately.

I might try something like the washer and sheath ideas, if nothing else works.

Can take a pic tomorrow of the area where the cable is breaking

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[Rhys_]

Righto, so had a good look at everything this morning. It appears as if the groove in the mech actuation arm has been worn into an irregular shape by the cable. However reconstructing the position of the snapped cable shows the majority of the breakage actually occurred at the interface where the groove changes to a 'slot' and is clamped.

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[mitchy_]

looks like the pinch bolt is being over tightened, fraying and breaking the cable. (your image shows the cable entering the clamp area backwards? but i assume that's just for the photo...)

use a soldered cable, and go easy on the bolt.

 

[Rhys_]

I've lightly filed and sanded all the sharp edges from the general area. Shall take it a bit easier on the bolt thanks mitchy

The cable is in the correct orientation in the picture, probs looks confusing because the that's the broken end piece in my fingers, not the other side of broken cable that goes back to the shifter

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[pharmaboy]

Agree, can't think of anything other than over tightening . Doesn't need to be tight just snug , but I can understand if you've had a cable slip during a ride, the natural reaction is to start really tightening the bastard up to stop it happening again - I always tighten stuff like that with only thumb and forefinger on the Allen key .

 

[Broken200]

Same problem with Saint Clutch derailleur

Hi,
I have the same issue with my Saint derailleur. Never snapped as many cables in my entire life since I have been running a clutch rear der. The Saint seems to make the cable be pulled side to side as you go from high to low gears etc. This over time combined with all the load the chain tensioning clutch transfers to the derailleur chews up cables at about one a month for me. I ride a fair bit and generally pretty rough trails so it definitely gets a workout but I think it could be designed a whole lot better. I find it hard to believe that during testing the riders didn't experience this issue. Only upside is that your increased maintenance (provided you catch it as soon as it starts to fray and not during a ride) leaves you with nice shifting cause your cable is always fresh...

 

[Rhys_]

Yep, agreed. I still do think there is something wrong with the way shimano have routed the cable on some of their latest mechs. Hopefully having the clamping bolt a little less snug will help take some of the pressure off in that region and extend the cable life. Shall have to get onto this increased maintenance business as well, little foreign to me at the moment!

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