legin
New member
Inspired to get on with it by posters like 911hillclimber I am off on an EU roadtrip in my 987.2 3.4 41k miles. Now the well known gearchange cable snapping has been playing on my mind given the total unpredictability and lack of prior warning. Just think what a total pita on a mountain pass , the AA will get you to a dealer somehow but short trip ruined and mega grief from the boss.
So after some thought where I was going to risk it I changed my mind 7 days before departure and decided that the only guarantee would come from replacement. I replaced the cables yesterday which took a day and I wont go into as its extensively covered elsewhere.
Cables replaced and no change in feel and no evidence of cable damage when I cut it open for a look - oh well at least I wont have cable anxiety.
Being an Engineer of course I couldnt leave it at that so decided to look closer and bearing in mind all the failures i have seen are catastrophic and after the event is there something to see and what fails first ? Guess what out of the two cables one failed the bend test, I actually heard some strands snap yet the other one was fine and I just could not break.
What does this tell then. The failure mode is fatigue in the internal strands and brought on by the number of cycles just like the paper clip. My assessment is that 70% strands snapped but of course as they snap the load goes up on the remaining ones which means failure soon comes. Who knows but probably had another 5 - 10 k left in the bag.
Some folk have reported a springy feel just before it gives up and this makes sense. Once the inner strands fail then only the steel containment coil remains which will of course stretch and compress with a very short life. So this is the nearest you get to a warning to get somewhere safe , be gentle and minimise gear changes the get it fixed.
What could you do.
You could live with the fix it on failure but for me given the places I go not acceptable, Im sure most folk wouldnt accept run to failure. In my opinion treat your cable like a service part which needs replacement not on age but gearchange cycles and if your a heavy user the maybe 30k and conversely motorway user 50k. Swap it every 30 - 35k and your covered at a cost much like a cambelt.
So after some thought where I was going to risk it I changed my mind 7 days before departure and decided that the only guarantee would come from replacement. I replaced the cables yesterday which took a day and I wont go into as its extensively covered elsewhere.
Cables replaced and no change in feel and no evidence of cable damage when I cut it open for a look - oh well at least I wont have cable anxiety.
Being an Engineer of course I couldnt leave it at that so decided to look closer and bearing in mind all the failures i have seen are catastrophic and after the event is there something to see and what fails first ? Guess what out of the two cables one failed the bend test, I actually heard some strands snap yet the other one was fine and I just could not break.
What does this tell then. The failure mode is fatigue in the internal strands and brought on by the number of cycles just like the paper clip. My assessment is that 70% strands snapped but of course as they snap the load goes up on the remaining ones which means failure soon comes. Who knows but probably had another 5 - 10 k left in the bag.
Some folk have reported a springy feel just before it gives up and this makes sense. Once the inner strands fail then only the steel containment coil remains which will of course stretch and compress with a very short life. So this is the nearest you get to a warning to get somewhere safe , be gentle and minimise gear changes the get it fixed.
What could you do.
You could live with the fix it on failure but for me given the places I go not acceptable, Im sure most folk wouldnt accept run to failure. In my opinion treat your cable like a service part which needs replacement not on age but gearchange cycles and if your a heavy user the maybe 30k and conversely motorway user 50k. Swap it every 30 - 35k and your covered at a cost much like a cambelt.
