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Old 01-17-07, 09:10 PM   #1
sknhgy 
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chain won't stay on big sprocket

I have a Trek 820. Just had it adjusted at bike shop. He's almost 2 hours away so I need to fix this myself.
Went for a ride today. When I shifted into high gear (large gear on front sprocket) I felt the shift lever go a little spongy at the end of it's travel, but I don't think I pressed on it overly hard. If I kept pressure on the shift lever, the chain would stay on the large sprocket. When I released pressure on the shift lever, the chain fell back on to the middle sprocket. I don't recall now if the indicator stayed on 3 or went back to 2.
Anyway, please help. I want to ride my bike.
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Old 01-17-07, 10:04 PM   #2
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The cage is probably getting out to the high limit screw before the shifter reaches the 3 detent. Try unscrewing the H limit screw on the front der mechanism half a turn. This may fix it, but it may allow you to shift the chain over the outside of the chainring, so be prepared for a surprise. If you overshift screw back the H limit screw, and loosen the tension in the front der cable (I think this will be a thumbwheel near the shifter), by turning clockwise 1/4 turn.
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Old 01-18-07, 04:49 PM   #3
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I kind of understand that. I guess......
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Old 01-18-07, 04:51 PM   #4
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Go to the park tool web site and read about adjusting a front der. Just take things one step at a time.
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Old 01-18-07, 09:21 PM   #5
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How old is the bike and what type of shifters do you have?
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Old 01-19-07, 07:57 PM   #6
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The bike was one year old on January 7th. It has Shimano v-brake shifters and I still ain't fixed it.
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Old 01-20-07, 12:07 AM   #7
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It sounds to me as if you need to increase the cable tension. Try 1/2 turn or so counter-clockwise on the front cable barrel adjustor, usually found where the front cable housing stops on the left side of the down tube. It's common for newer bikes to loose some shift cable tension.

Al
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Old 01-20-07, 02:53 AM   #8
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Quote:
Originally Posted by sknhgy
The bike was one year old on January 7th. It has Shimano v-brake shifters and I still ain't fixed it.
Vbrake shifters? wha?
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Old 01-20-07, 08:49 PM   #9
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I thightened the cable at a clamping point down near the sprockets.
That seemed to help.
Thanks
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