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Old 07-24-07, 06:29 AM   #1
EazyDuz
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Hi im new, gearing problem

Im not sure if it IS a problem or not.
Basically ive been having trouble with my gears. For about an hour ive been tuning the derailleurs and everything seems ok, havnt test rided it yet though.
My bike has 3 chain rings, and 5 gears. So thats 15 different gear combinations. Basically if im in the 3rd chain ring, and the 5th gear, if i back pedal the chain comes off the 5th gear and drops into 4th and sometimes third. If i forward pedal it will go back into 5th (where it should be). Is this supposed to happen as you arent really meant to back pedal on a bike. Its just if im on 1st gear on 3rd chain ring or 5th gear on second chainring i can backpedal just fine.

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Old 07-24-07, 08:32 AM   #2
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It sounds as if you may have just a bit too much tension on the rear shift cable. But if everthing works OK when riding don't worry about it.

Al
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Old 07-24-07, 08:54 AM   #3
rschulze
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If your rear drllr hanger is bent, this can happen as well. It tracks true when going forward but shifts up or down when back pedaling. A decent bike shop can check this out and in most cases tweak the hanger pretty quickly. If your bike has ever been in a wreck or fallen on the drive side, this might be something to look into.
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Old 07-25-07, 12:14 AM   #4
Michel Gagnon
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If I understand correctly, the derailleur hasn't been moved and doesn't move by itself. It's the chain that moves on the cogs when you backpedal. So there is no relation to a bent or unbent derailleur hanger.

When one backpedals, it's the upper section of the chain that shifts. Basically it happens because at some point, the chain is oblique to the cogs. Reasons:

Oblique rear wheel. Especially possible on an older bike with horizontal dropouts. If the wheel is not installed properly, it will be oblique and the freewheel or cassette will be oblique. On newer bikes with vertical dropouts, it's almost impossible to do.

Oblique chainline. If the cogs are too much inboard or the crankset too much outboard, then the chain is oblique. No problem when you pedal forward, because the derailleur keeps the chain in place. But when you backpedal, the oblique chain tries to shift and may succeed when it reaches the "ramp" which is precisely designed to help indexed shifting. the only solution might be to put the crankset more inboard or outboard, probably with a washer on the bottom bracket or with a spindle of a different length.

- Bent cog. If you have a bent cog, it may help derail the chain. Slowly pedal forward or backward and look at the chain and/or cog to see if it wobbles in one point. If that's the problem, the only solution is to change the cog or cassette.

In all those situations, a clean chain might help.
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Old 07-25-07, 05:58 AM   #5
EazyDuz
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The chain is new and oiled.
However, when i thought it was all tuned properly, when i actually rode the bike the gears stopped working as they should. If i shift down a gear to quickly the chain will jump and come off.
I have no practice of doing this anyway, so im taking it to a professional to do for me. I tried for 3 hours and when i thought it was right, everything changed when i test rided it.
Oh well.
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Old 07-25-07, 08:23 AM   #6
Al1943
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Quote:
Originally Posted by EazyDuz View Post
The chain is new and oiled.
However, when i thought it was all tuned properly, when i actually rode the bike the gears stopped working as they should. If i shift down a gear to quickly the chain will jump and come off.
I have no practice of doing this anyway, so im taking it to a professional to do for me. I tried for 3 hours and when i thought it was right, everything changed when i test rided it.
Oh well.
You just need some good instructions. Checkout the instructions at http://www.parktool.com
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Old 07-25-07, 08:35 AM   #7
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sounds like an oblique wheel too me... I had the same problem yesterday and I brought my wheel to my LBS to get the axel spaced... works like a charm now.
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Old 07-30-07, 01:43 AM   #8
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IVe tuned the derailleurs now. The bike shifts fine, its just when i backpedal the chain can come off depending on the gear. If its a low chainring and a high gear, it wont come off when backpedalling, if its a low chainring and a low gear it does come off because the chain is in a more diagonal position.
Is this not normal?
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