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Discussion Starter · #1 · (Edited)
My bike likes to pop down a gear when I am on ascents, especially when I am out of the saddle. I can't seem to figure out was is causing it other than some apparent stress on the rear derailuer I guess... today the chain popped off. It was easy to get back on, but annoying that I had to stop halfway up a hill.

Any ideas?
 

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There's a bunch of reasons. Wear and tear. Bent derailleur. Bent derailleur hanger. Chain too long and probably some more.

Or it could be a combination. Look at your bike and see... clue us in.
 

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jsedlak said:
My bike likes to pop up a gear when I am on ascents, especially when I am out of the saddle. I can't seem to figure out was is causing it other than some apparent stress on the rear derailuer I guess... today the chain popped off. It was easy to get back on, but annoying that I had to stop halfway up a hill.

Any ideas?
Is your bike frame stiff or whippy? If you are a strong climber, you may "bend" the frame enough when pedaling to change the cable length in relation to the frame and cause it to change gears. I would play around with the shifter cable length adjusters, a cable may be a little too tight or a little too loose, so you are on the verge of shifting, so a little deflection of the frame may cause it to complete the shift.
 

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Discussion Starter · #4 ·
Define whippy?

I just had a check on the bike and it seems that nothing is bent or bending. And I'll have to make a correction in that the bike is going to a lower gear on the rear. (Bigger gear ratio, smaller cog, harder to push, etc)
 

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jsedlak said:
Define whippy?

I just had a check on the bike and it seems that nothing is bent or bending. And I'll have to make a correction in that the bike is going to a lower gear on the rear. (Bigger gear ratio, smaller cog, harder to push, etc)
Does the bike flex under you when you're standing on the pedals and crankin? But more likely is that your deraileur needs a slight adjustment. It's likely that you're just enough out of alignment that the deraileur is positioned too much to the inside of each gear. Just turn the adjusting barrel at the deraileur to the right a notch or two and see what happens.
 

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Possible issues could be as simple as needing adjust the shifter cable to possibly a bent dérailleur to worn out parts. Which gear does it do the "ghost shifting"? Take a good look at the cassette while the spinning chain backwards. Look for any bent teeth in the cassette. Is their any hopping of the chain while spinning backward. See if the derailleur is lined up with the cassette. Check the chain to make sure there is no tight links. Look at the hanger. Does it look bent? If everything looks good then try to adjust with barrel adjuster on the rear derailleur. If you don feel confident doing this then take it to your LBS. My MTB had similar issues and it turned out to be a combination of the above mentioned things.
 

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Check the cable guide under the bottom bracket shell for dirt or some obstruction; clean and lube if needed. Too much friction between the cable and the cable guide can cause exactly what you describe.
 

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Whoa. I do believe you meant turn the barrel adjuster left.

Was98strat said:
Does the bike flex under you when you're standing on the pedals and crankin? But more likely is that your deraileur needs a slight adjustment. It's likely that you're just enough out of alignment that the deraileur is positioned too much to the inside of each gear. Just turn the adjusting barrel at the deraileur to the right a notch or two and see what happens.
 

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Turn the black plastic adjuster thingy near the rear deraileur 1/4 turn in one direction. If it still does it turn another 1/4 turn. In less than 1 full turn it should fix it. Make sure you can shift to the largest rear gear and the smallest rear gear. If it doesn't you need to turn that thing the other way to where it was and adjust in the opposite direction 1/4 turn at a time.
 

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Discussion Starter · #11 ·
edhchoe said:
Turn the black plastic adjuster thingy near the rear deraileur 1/4 turn in one direction. If it still does it turn another 1/4 turn. In less than 1 full turn it should fix it. Make sure you can shift to the largest rear gear and the smallest rear gear. If it doesn't you need to turn that thing the other way to where it was and adjust in the opposite direction 1/4 turn at a time.
I'll have to try this... today I wasn't having a problem. It felt like it was going to go but then nothing. However I made adjustments up front to get my big ring to be reachable and now the bike throws the chain off everytime I shift up front. Guess I have a lot more to learn about the deraileur tunes.
 

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Wait. Throws the chain off where? In the front? Which direction? Into the bike or away from the bike? I thought your problem was ghostshifting inn the rear??

jsedlak said:
I'll have to try this... today I wasn't having a problem. It felt like it was going to go but then nothing. However I made adjustments up front to get my big ring to be reachable and now the bike throws the chain off everytime I shift up front. Guess I have a lot more to learn about the deraileur tunes.
 

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Discussion Starter · #13 ·
OES said:
Wait. Throws the chain off where? In the front? Which direction? Into the bike or away from the bike? I thought your problem was ghostshifting inn the rear??
hahahahaha in the front in both directions. But this is a different front I am fighting this bike on. Until now the front deraileur wouldn't let me reach the bigger ring. So I tuned it a bit so I could get to both rings, but I overtuned it so the chain just gets thrown off the rings.

Not a big deal, I just have to tighten down how far the deraileur can move in each direction until it is perfect.
 
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