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Old 05-20-07, 07:34 PM   #1
yura
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Transmission Twitching

Hello fellow bikers,
I've just tuned up the transmission on an old Falcon rally bike (which ran fine until now).
Everything was fine when I flipped it over, and did the adjustments etc.
It was only when I started riding it, I noticed that the rear derailler seems to jolt when a certain amount of force is applied onto the pedals, apperantly only when the highest 2 gears are in use. I'm not sure exactly what exactly is happening, but it's very frustrating because I can't generate enough force to recreate this when the bike is stationary. It's strange because the derailler and all the gears seem to be alligned.
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Old 05-20-07, 07:42 PM   #2
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It sounds like the chain is slipping. How worn are the chain and cassette?
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Old 05-20-07, 09:23 PM   #3
yura
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The chain is fine, but if by cassette you mean the gear wheels I have to check. So you think the cahin starts to slip because it's too loose?
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Old 05-20-07, 10:08 PM   #4
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i think he means more that the teeth on the gears are getting chipped and rounded making it harder for the chain to keep a good grip on the gears. this is less of an issue on the lower gears because there are more teeth for the chain to grab onto
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Old 05-21-07, 10:54 AM   #5
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Ya that makes sense. It is a pretty old bike I think from the mid 70's. I guess for now I'll just have to not use the highest gears (and not do any speeding) until it annoys me enough to get a new wheel.
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Old 05-21-07, 12:06 PM   #6
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Quote:
Originally Posted by yura
The chain is fine...
How do you know that it's fine?
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Old 05-23-07, 06:00 PM   #7
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It doesn't appear to be damaged with small cracks and seems to be in good condition. Could it be stretched?
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Old 05-24-07, 11:27 AM   #8
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Chains don't stretch, but wear makes them get "longer". Measure 24 half-links (each inner and outer is a half link). A new chain will measure 12" exactly. 12 1/16" is marginal. Anything much over that is seriously worn. If the chain is badly worn, it's almost a sure bet that the cassette (small cog set) needs to be replaced too.

http://sheldonbrown.com/chains.html#wear
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