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#1
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casette shifting, again
Maybe you remember my problem with the smaller
sprockets being unreachable. After degreasing and lubing the whole thing it got better, but then the problem returned and now worse than ever. Because of the constant rain and snow here, I thought, OK, so it needs lube to work, and the water washes it away. But eventually I got tired of it and now I have a new cable and it works great. Every single sprocket is reachable. Maybe tomorrow it won't work again. But let's assume it still works, so questions: 1) Does this makes sense in theory? If the cable was shot, doesn't that mean the bigger, not the smaller sprockets being unreachable? 2) Except for the obvious cases when the cable is all stiff and bent, how can one examine/determine its quality? 3) I don't know how much this bike has been used, but it looks very unused. The brake discs are, at least. I've used it every day a couple of months, for a time ~20km/day, but more often less than that. Is this enough to wear out a cable? How long does a cable last? -- underground experts united http://user.it.uu.se/~embe8573 |
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#2
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casette shifting, again
On 12/12/2018 12:16 PM, Emanuel Berg wrote:
Maybe you remember my problem with the smaller sprockets being unreachable. After degreasing and lubing the whole thing it got better, but then the problem returned and now worse than ever. Because of the constant rain and snow here, I thought, OK, so it needs lube to work, and the water washes it away. But eventually I got tired of it and now I have a new cable and it works great. Every single sprocket is reachable. Maybe tomorrow it won't work again. But let's assume it still works, so questions: 1) Does this makes sense in theory? If the cable was shot, doesn't that mean the bigger, not the smaller sprockets being unreachable? I think what you found makes perfect sense. It's your muscles that pull the cable to shift to the bigger sprockets. It's only the small springs in the derailleur that drag the cable back to allow shift to the small sprockets. If the cable is rusted, kinked, etc. the springs will have a hard time. But as we may have said before, it's not necessarily the cable itself. I've experienced shifting problems caused by friction and/or dirt where the cable passes through a channel under the bottom bracket. Cleaning and lubricating there fixed the problem. Also, if housing ends are not cut square, their edges may drag on the cable. That should be visually obvious. 2) Except for the obvious cases when the cable is all stiff and bent, how can one examine/determine its quality? I suppose one could pull alternately on each end of the cable to be sure it slides freely. Or do the same before and after the cable passes through a section of housing. The 180 degree housing just before the derailleur is sometimes a problem. I had an early mountain bike that used cable housing in a U shape to turn the front derailleur's cable from the downtube to the seat tube. The ends of that housing faced upward, and would catch water and cause rust or ice to form inside. The problem could be felt by tugging the cable. 3) I don't know how much this bike has been used, but it looks very unused. The brake discs are, at least. I've used it every day a couple of months, for a time ~20km/day, but more often less than that. Is this enough to wear out a cable? How long does a cable last? In my experience, cables last almost forever if they are lubricated every few years. And lots of modern cable housing is lined and doesn't require lubrication. The exception is a cable that undergoes sharp bend, such as the end of a shift cable that wraps tightly around a shift lever. I can feel when one of those starts snapping individual strands. Then it's time for replacement. -- - Frank Krygowski |
#3
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casette shifting, again
On Wed, 12 Dec 2018 18:16:47 +0100,
Emanuel Berg wrote: Maybe you remember my problem with the smaller sprockets being unreachable. After degreasing and lubing the whole thing it got better, but then the problem returned and now worse than ever. Because of the constant rain and snow here, I thought, OK, so it needs lube to work, and the water washes it away. But eventually I got tired of it and now I have a new cable and it works great. Every single sprocket is reachable. Maybe tomorrow it won't work again. But let's assume it still works, so questions: 1) Does this makes sense in theory? If the cable was shot, doesn't that mean the bigger, not the smaller sprockets being unreachable? It makes complete sense to me, for the reasons Frank gave. Recently I had the same problem, my rear derailer would not shift to the smaller cogs without some help (i.e., pushing outward on the derailer). Lubing the cable in the housing did not help, and when I looked more closely I found that at least one strand of the cable had broken and was frayed away from the cable where it exited the rear of the front section of housing (i.e., under the down tube). I tried to replace the cable, but could not pass it through the old housing--so something inside of the housing had been damaged (or there was still a fragment of a cable strand embedded inside it). After replacing the housing, I was able to easily pass the new cable through it and the shifting worked well again. -- Ted Heise West Lafayette, IN, USA |
#4
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casette shifting, again
On Wednesday, December 12, 2018 at 9:16:50 AM UTC-8, Emanuel Berg wrote:
Maybe you remember my problem with the smaller sprockets being unreachable. After degreasing and lubing the whole thing it got better, but then the problem returned and now worse than ever. Because of the constant rain and snow here, I thought, OK, so it needs lube to work, and the water washes it away. But eventually I got tired of it and now I have a new cable and it works great. Every single sprocket is reachable. Maybe tomorrow it won't work again. But let's assume it still works, so questions: 1) Does this makes sense in theory? If the cable was shot, doesn't that mean the bigger, not the smaller sprockets being unreachable? 2) Except for the obvious cases when the cable is all stiff and bent, how can one examine/determine its quality? 3) I don't know how much this bike has been used, but it looks very unused. The brake discs are, at least. I've used it every day a couple of months, for a time ~20km/day, but more often less than that. Is this enough to wear out a cable? How long does a cable last? -- underground experts united http://user.it.uu.se/~embe8573 I use stainless cables and housings now and haven't had any troubles from that reason but I see where it could if you're using steel cables and especially those "Teflon" coated cables which very rapidly peal the non-stick coating off. A source of this problem I used to have is the joints in the rear derailleur wearing and jamming somewhat. Since the return spring is near zero pressure near the bottom is doesn't require a whole lot of additional friction to keep it from bottoming out. |
#5
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casette shifting, again
Theodore Heise wrote:
It makes complete sense to me, for the reasons Frank gave. Recently I had the same problem, my rear derailer would not shift to the smaller cogs without some help (i.e., pushing outward on the derailer). Lubing the cable in the housing did not help, and when I looked more closely I found that at least one strand of the cable had broken and was frayed away from the cable where it exited the rear of the front section of housing (i.e., under the down tube). Yes, that makes sense in the "cable damage" sense, but not in the "cable extension" sense, because then the shifting problem would be the opposite, right? But perhaps this is what happens to the cable, it get damaged so it interferes with the housing? How does this damage happen BTW? I thought the general problem was the cable loosed its integrity or internal strength, so it got just a bit longer, much like a bicycle chain, but enough to mess things up? Also, as for lubing, how is this done? Remove the housing, pull out the cable, drip into the housing and then pull the cable back and forth to distribute the oil? Seems like a lot of work! How often is this typically done? -- underground experts united http://user.it.uu.se/~embe8573 |
#6
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casette shifting, again
On 12/12/2018 4:58 PM, Emanuel Berg wrote:
I thought the general problem was the cable loosed its integrity or internal strength, so it got just a bit longer, much like a bicycle chain, but enough to mess things up? The cable itself is not going to get stretched with use, if that's what you mean. That would require forces many, many times larger than what's being applied in normal operation. Also, as for lubing, how is this done? Remove the housing, pull out the cable, drip into the housing and then pull the cable back and forth to distribute the oil? Seems like a lot of work! How often is this typically done? I find it easier to loosen the clamp screw at the derailleur or brake, remove any cable end anti-fray gizmo, pull out the cable, wipe it down with a light coat of oil, then thread it back through the housing and re-clamp. Re-do any anti-fray measure. The housing can stay in place. If the cable runs through external cable guides, be sure those too are clean and lubricated. At the risk of sounding obsessive, paraffin wax works pretty well as a dry lubricant on such surfaces. -- - Frank Krygowski |
#7
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casette shifting, again
On Wed, 12 Dec 2018 22:58:25 +0100,
Emanuel Berg wrote: Theodore Heise wrote: It makes complete sense to me, for the reasons Frank gave. Recently I had the same problem, my rear derailer would not shift to the smaller cogs without some help (i.e., pushing outward on the derailer). Lubing the cable in the housing did not help, and when I looked more closely I found that at least one strand of the cable had broken and was frayed away from the cable where it exited the rear of the front section of housing (i.e., under the down tube). Yes, that makes sense in the "cable damage" sense, but not in the "cable extension" sense, because then the shifting problem would be the opposite, right? Not sure about this. I think it's two different failure modes, and if the cable length changes it affects shifting across all (or nearly all) of the cassette. But perhaps this is what happens to the cable, it get damaged so it interferes with the housing? How does this damage happen BTW? In my case it was because one of the cable strands had fractured, and most likely the factured end (or the frayed strand) damaged the inside surface of the housing--or became lodged in it. -- Ted Heise West Lafayette, IN, USA |
#8
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casette shifting, again
On Wed, 12 Dec 2018 17:15:45 -0500,
Frank Krygowski wrote: On 12/12/2018 4:58 PM, Emanuel Berg wrote: I thought the general problem was the cable loosed its integrity or internal strength, so it got just a bit longer, much like a bicycle chain, but enough to mess things up? The cable itself is not going to get stretched with use, if that's what you mean. That would require forces many, many times larger than what's being applied in normal operation. I think that's correct, and yet on my tandems I've sometimes seem some changes in shifting that I attribute to change in cable length--maybe more due to temperature changes than to actual physical stretching. For example, when we go out on a very warm day after having ridden in cold weather for a time, I often have to tighten the adjuster just a smidge. -- Ted Heise West Lafayette, IN, USA |
#9
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casette shifting, again
On Wed, 12 Dec 2018 22:58:25 +0100, Emanuel Berg
wrote: Theodore Heise wrote: It makes complete sense to me, for the reasons Frank gave. Recently I had the same problem, my rear derailer would not shift to the smaller cogs without some help (i.e., pushing outward on the derailer). Lubing the cable in the housing did not help, and when I looked more closely I found that at least one strand of the cable had broken and was frayed away from the cable where it exited the rear of the front section of housing (i.e., under the down tube). Yes, that makes sense in the "cable damage" sense, but not in the "cable extension" sense, because then the shifting problem would be the opposite, right? But perhaps this is what happens to the cable, it get damaged so it interferes with the housing? How does this damage happen BTW? I thought the general problem was the cable loosed its integrity or internal strength, so it got just a bit longer, much like a bicycle chain, but enough to mess things up? Also, as for lubing, how is this done? Remove the housing, pull out the cable, drip into the housing and then pull the cable back and forth to distribute the oil? Seems like a lot of work! How often is this typically done? Or you can buy cable that is plastic coated and never needs oiling :-) cheers, John B. |
#10
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casette shifting, again
On 12/12/2018 5:29 PM, Theodore Heise wrote:
On Wed, 12 Dec 2018 17:15:45 -0500, Frank Krygowski wrote: On 12/12/2018 4:58 PM, Emanuel Berg wrote: I thought the general problem was the cable loosed its integrity or internal strength, so it got just a bit longer, much like a bicycle chain, but enough to mess things up? The cable itself is not going to get stretched with use, if that's what you mean. That would require forces many, many times larger than what's being applied in normal operation. I think that's correct, and yet on my tandems I've sometimes seem some changes in shifting that I attribute to change in cable length--maybe more due to temperature changes than to actual physical stretching. For example, when we go out on a very warm day after having ridden in cold weather for a time, I often have to tighten the adjuster just a smidge. I think apparent increases in cable length are probably due to shifting of position of the cable inside the housing, or wear of the housing where the cable follows it through curves, or the end of the housing settling further into a housing stop. Maybe the temperature change triggers something like that? As I've mentioned, my most frequent index shifting adjustment happens with my folding bike, especially if its sat folded for a while. I've learned it's easiest to just change the levers to friction mode for a while, then re-try the index mode. Somehow, most of the misadjustment corrects itself - I guess by the cables settling into their old equilibrium position. I'm pretty sure that if it were feasible to run the shift cable through a straight, rigid tube all the way from shifter to derailleur, I'd never see that problem. -- - Frank Krygowski |
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