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shifting today-->chain stuck, almost fell

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shifting today-->chain stuck, almost fell

Old 03-20-11, 03:58 PM
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fatslowbiker
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shifting today-->chain stuck, almost fell

Hi,

I am running Shimano 105 and recently got my bike tuned up. I was told that my front shifter was broken and it was therefore replaced (I would sometimes have to double-tap to shift and sometimes it took several tries). Also got a new chain.

About 200 miles later, I think the problem has come up again. I am having trouble shifting from the small chainring to the larger one. I only shift to the small chainring when I am returning from my ride (read somewhere that it's better to store the bike this way). Today, I tried shifting, nothing happened at first, did the double-shift, and the chain got stuck...couldn't pedal. Fortunately, I was going fast enough and didn't fall over.

Anyone know what's going on? Thanks
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Old 03-20-11, 04:21 PM
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reptilezs
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if the shop used new housing and cable(they should have) then the cable tension might need some index adjustment. a good mechanic would have prestressed the cable system to remove 90 percent of the slack and bed in process. i would bring it back and let them know you want it fixed
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Old 03-20-11, 04:46 PM
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Stuck?? stuck where exactly. If it was between the chainrings, your chain is too narrow for the crankset. If it was a simple case of non-completed shift it's possible that the FD wasn't adjusted properly, or that the cable slackened, either by slipping in the pinch bolt, or as the head and ferrule settled as they sometimes do on new installs.

But this brings up a second question.

When I see folks having chronic FD issues, I look to the rider as a possibility. Don't be offended because I don't know you or your skill level, but you might be the cause of your own problems.

The FD works on the upper loop of the chain which is under tension, so if you don't ease up pedal pressure significantly it has trouble generating the force needed to lift the chain to the larger ring against the tension you're putting into it. FD's much more than RDs need your help to shift, and pedal pressure must be near zero or just enough to keep the cranks turning during the shift.
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Old 03-20-11, 07:15 PM
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fatslowbiker
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Originally Posted by FBinNY View Post
Stuck?? stuck where exactly. If it was between the chainrings, your chain is too narrow for the crankset. If it was a simple case of non-completed shift it's possible that the FD wasn't adjusted properly, or that the cable slackened, either by slipping in the pinch bolt, or as the head and ferrule settled as they sometimes do on new installs.
I'm not really sure if "stuck" is the right word, but basically it was jammed so that I couldn't pedal. I backpedaled, the chain went on, and it shifted again.

Thanks for the advice. It may very well be me...I definitely do try to ease up pressure when shifting with both the FD and RD, but maybe it's not enough. I don't even shift the FD that much, only at the end of my ride when I'm putting the bike away.
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Old 03-20-11, 07:24 PM
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I had that one with my ultegras. I went to sachs downtube shifters and never looked back.

IMHO, I think the Brifters are more complicated than they should be.

I agree that there could be some slack issues. I would take it back to the LBS and have them stand behind their work. If need be have them put you on a trainer and have them look at your technique.
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Old 03-20-11, 07:30 PM
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Now that you described it better, I thought of another possibility.

If the FD is too high, it's possible to gt the chain jammed between an FD cage plate and the chainring. I suggest that because backpedaling is how you clear that. Drop the chain out of the way, and shift the FD to the upper ring. You there should be about 1/16" or 2mm gap between the chainring and the outer plate. if there's too much problems like yours can occur.

But in any case test the FD shifting first off the ground, then if that's OK, practice while doing light riding in a parking lot someplace while you're not tired and there's no real riding load. If it works in the lot, then, I suspect it's a matter of your being tired and losing some hand foot coordination at the end of your rides.

One last note. Some folks have less mobility or strengh in the fingers, had or wrists, and have problems throwing the lever far enough without rotating their whole are out and around. If that sounds like you, try this technique that I know works with Campy lefts, but I'm not as sure will work on 105 (I don't ride Shimano).

When you're getting ready to shift swing the lever across until you hear or feel the cage hit the chain, then relax let it swing back then sweep the lever and complete the shift crisply.
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Last edited by FBinNY; 03-20-11 at 07:38 PM.
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