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Gear cables snapping after 2000 miles in same place

Will NunezWill Nunez Posts: 203
edited November 2012 in Workshop
Gear cable (rear gear) keeps snapping under hood. Now on fifth cable, usually last between 2 and 3 thousand miles. Shimani 105 5700 all round. 80% commute miles (lots of gear changing for junctions). Avg mileage 200 miles a week. Shop replaced lever after 10000 miles, thinking it couldbe that. After this mornings snap, it clearly isnt. I regularly lube cables and maintain derailleur.

Any ideas what could be causing it. My last bike had one cable change in 12000 miles, and that was purely because the rear wheel ate the derailleur and it all needed replacing
Current Stock:
Carrera Vanquish '08
Orbea Onix T105 '11
Carrera Fury '07

Posts

  • majormantramajormantra Posts: 2,094
    Did you replace the outer when you changed the lever? My guess is there's something wrong with the routing where it enters the lever.
  • I think the Shimano design allows for some friction... I had cables freying on Shimano 105 (I think it was 5600) which has never happened on Campagnolo or the more recent Tiagra 4500.
    Don't know what to advise...
  • Did you replace the outer when you changed the lever? My guess is there's something wrong with the routing where it enters the lever.

    Shop did it will ask question
    Current Stock:
    Carrera Vanquish '08
    Orbea Onix T105 '11
    Carrera Fury '07
  • I suppose a question is, is this typical or is this outside the bounds of reasnable expectation for a gear cable
    Current Stock:
    Carrera Vanquish '08
    Orbea Onix T105 '11
    Carrera Fury '07
  • dodgydodgy Posts: 2,890
    Will Nunez wrote:
    I suppose a question is, is this typical or is this outside the bounds of reasnable expectation for a gear cable

    He's getting the same mileage out of his cables that most people see out of their tyres. Something is definitely wrong.
  • keef66keef66 Posts: 13,286
    My 5600 rear cable frayed inside the shifter after about 2500 miles. (erratic shifting gave the game away) Not inspected the replacement recently; might have a peek tonight.

    You using Shimano cables? I noticed when I was looking for a replacement that some of the non-Shimano aftermarket stuff had subtly different shaped / sized ends, so to be sure I bought a Shimano cable online.
  • Always shimano. PTFE Coated ones when i can get them
    Current Stock:
    Carrera Vanquish '08
    Orbea Onix T105 '11
    Carrera Fury '07
  • dodgy wrote:
    Will Nunez wrote:
    I suppose a question is, is this typical or is this outside the bounds of reasnable expectation for a gear cable

    He's getting the same mileage out of his cables that most people see out of their tyres. Something is definitely wrong.


    I expect 4000 from my tyres :mrgreen:
    Current Stock:
    Carrera Vanquish '08
    Orbea Onix T105 '11
    Carrera Fury '07
  • Took bike to LBS (Paul hewitts in Leyland) they cant get to bottom of it. They said they have had a few Shim 105 bikes lose cables with low milege but not regularly from same customer. Just advised me to change cable every 1800 miles. Not ideal, but not much else they can do I suppose.

    Worth the visit though, bottom bracket worn. Should have got 4000 miles from it, it had just done over 12000 miles!
    Current Stock:
    Carrera Vanquish '08
    Orbea Onix T105 '11
    Carrera Fury '07
  • dodgydodgy Posts: 2,890
    A bottom bracket should be easily good for 4000miles! I've never had to replace one on a road bike, usually keep them for 3 years and put 10000 miles on them before selling with the original BB.
  • Never in over 20 years of cycling have I had a gear cable break. Set of cables on one bike were installed in 1996 and are still fine, changed levers and kept the same cables as they were still fine.

    Sounds like you have some sort of problem at the lever end. I'd take the levers off and check them out, there must be something wrong either with the lever at the point the cable is breaking or with the outer.

    At least it isn't your brake cable!
  • Monty DogMonty Dog Posts: 20,614
    I suspect there's a burr / rough edge inside the ratchet head of the shifter - Shimano STi can have a rep for fraying cables at the head, but not to this degree. You could try using a fine, rat-tail file inside the nipple seat.
    Make mine an Italian, with Campagnolo on the side..
  • But the shifter was replaced at 10000 miles (4 cables all snapping in hood) for a new one, and the new one broke a cable at the same average as the others. I was thinking today and its a long shot that maybe the derailleur is too stiff hence increased tension so may look to see what i can do about that.
    Current Stock:
    Carrera Vanquish '08
    Orbea Onix T105 '11
    Carrera Fury '07
  • Hi,
    Maybe a long shot but is the bar tape being removed when replacing the cable. It is possible to feed the cable through and under the bar tape, but to me it sounds like something catching the cable and weakening it. This could be a fray of the outer cable on the end that meets the shifter, and the only way to check this would be to remove the bar tape.
    Just a thought but maybe worth a try!
    Danny.
  • Thanks for the reply. Outer cable was replaced at cable number 3. and I think replaced again with shifter after cable 4. I did ask. I can see outer cable tip by lifting hood rubber anyway. Will have a good look at weekend, its now done a 600 miles since last break so will look for signs of wear. Its a replace everything that touches the chain and has teeth maintenance job this weekend, front chain ring starting to look like ninja weapon. Will also look at derailleur stiffness too. Who says cyclings cheap :-( £100 of parts awaiting fitment
    Current Stock:
    Carrera Vanquish '08
    Orbea Onix T105 '11
    Carrera Fury '07
  • £100 of parts = 2 weeks petrol for a lot of people! and then they pay to go on an exercise bike in a gym!
  • :mrgreen: This is deviation, but I work on 50 calories per mile. 32 miles per day, 1600 cals ber day, approx 3 sandwiches = £6 which is the same as petrol ;-). But agree. no Gym membership
    Current Stock:
    Carrera Vanquish '08
    Orbea Onix T105 '11
    Carrera Fury '07
  • Monty DogMonty Dog Posts: 20,614
    Might be thought as heresy, but try changing to a Campagnolo-branded cable? The nipple head is slightly narrower and the cables slightly thinner / more flexible - a bit more wiggle-room may eliminate the problem. Also check for burrs on the end of the outer cable.
    Make mine an Italian, with Campagnolo on the side..
  • Cheers monty. Will try that at next replace
    Current Stock:
    Carrera Vanquish '08
    Orbea Onix T105 '11
    Carrera Fury '07
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