rear derailleur not changing into higher gears
Discussion
had an interesting spinning ride into work this morning. i got into a low gear to ride up a hill, then when i tried to change up a gear or two the rear derailleur wouldn'd move. the shifters made all the right noises but derailleur wouldn't budge. so i was stuck in a low gear all the way to work and looked like a right amateur, spinning away on the flats.
l looked at the cable and noticed that if i lightly used the shifter to change down a gear i could see the cable tensioning, but when you change up the cable didn't move at all.
could there be a problem with the spring in the derailleur or perhaps some muck on the cable that is stopping in from moving properly? i'll take it apart tonight and have a look, but any advice / ideas in the meantime would be very welcome!
l looked at the cable and noticed that if i lightly used the shifter to change down a gear i could see the cable tensioning, but when you change up the cable didn't move at all.
could there be a problem with the spring in the derailleur or perhaps some muck on the cable that is stopping in from moving properly? i'll take it apart tonight and have a look, but any advice / ideas in the meantime would be very welcome!
Sounds like the outer 'sheath' cable may be the problem. Since changing down requires you to pull the cable against the tension, and changing up requires that the spring pulls back - if the spring is fine (which is almost always the case), then the culprit is likely to be friction between the gear cable and the outer sleeve somewhere. This can be a ball ache if it's the one under the bar tape...
Could be a couple of things causing this.
I assume the derailleur is on the low gear (large cog on rear cassette) and that it won't drop down to the smaller cogs when you use the shifter?
If you can pop the wheel out, release all cable tension by using the shifters to change gear to what would be the smallest cog and you should then be able to move the derailleur by hand. Does it move smoothly? If not, might just need a thorough clean and re-lube?
Might be that your gear cables are full of gunge. Strip them and give them a re-lube.
Might be that your gear cables are on the way out. They might have a kink on the inner which is hidden inside the outer. Might be fraying somewhere inside the outer cable, or within the shifter unit causing friction and stopping the derailleur from dropping down?
Had any 'off's recently causing the drailleur hanger to be bent or damage to derailleur itself? Maybe just a small knock from other people leaning their bike against yours in the bike shed at work, clonked it on something when putting it in your car / garage / shed / bedroom ?
I assume the derailleur is on the low gear (large cog on rear cassette) and that it won't drop down to the smaller cogs when you use the shifter?
If you can pop the wheel out, release all cable tension by using the shifters to change gear to what would be the smallest cog and you should then be able to move the derailleur by hand. Does it move smoothly? If not, might just need a thorough clean and re-lube?
Might be that your gear cables are full of gunge. Strip them and give them a re-lube.
Might be that your gear cables are on the way out. They might have a kink on the inner which is hidden inside the outer. Might be fraying somewhere inside the outer cable, or within the shifter unit causing friction and stopping the derailleur from dropping down?
Had any 'off's recently causing the drailleur hanger to be bent or damage to derailleur itself? Maybe just a small knock from other people leaning their bike against yours in the bike shed at work, clonked it on something when putting it in your car / garage / shed / bedroom ?
Very simple to diagnose, perhaps wait until you get home tho:
1) grab hold of the cable where it runs down the underside of the big tube (presumably un-sheathed). Pull hard and shift the gears around - if that inner moves, then it's not the shifters
2) undo the pinch bolt that holds the cable onto the rear mech. If the mech now springs to the outside, the mech is probably good (move it in with your hand, there should be a fair amount of resistance)
If 2 is OK, you need new cable
If 2 isn't, then probably a new mech.
If you fail 1 probably the shifter.
Of course you'll then have to figure out how to set up the gears again - take a look on the park tool website; IIRC they have a pretty good guide.
1) grab hold of the cable where it runs down the underside of the big tube (presumably un-sheathed). Pull hard and shift the gears around - if that inner moves, then it's not the shifters
2) undo the pinch bolt that holds the cable onto the rear mech. If the mech now springs to the outside, the mech is probably good (move it in with your hand, there should be a fair amount of resistance)
If 2 is OK, you need new cable
If 2 isn't, then probably a new mech.
If you fail 1 probably the shifter.
Of course you'll then have to figure out how to set up the gears again - take a look on the park tool website; IIRC they have a pretty good guide.
The problem as said above is almost never the actual mech its self, nearly always the cable. How old is the cable? They don't last that long, if its seen a year of action in all weathers then I would change the outer and the cable, probably cost you less than ten quid and will make the shifting feel brand new.
Got home, took the wheel off and played with the derailleur. Removed the cable, cleaned it, oiled it, thoroughly cleaned the derailleur and payed with the shifters. Noted that without the wheel the change down was fine (as before) and the change up was better but 'lazy' ie it dd move but slowly. However when I moved the derailleur by hand it sprang back and forth perfectly. Put the wheel back on and the gears do nw work but the change up is still slow and lazy. Do you think this is just gunk that has built up in the cable housing causing friction against the cable?
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