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8 Speed Drivetrain Issue

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8 Speed Drivetrain Issue

Old 06-22-09, 06:33 PM
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ChadFM
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8 Speed Drivetrain Issue

I recently upgraded my (mtb) wheelset, and while doing so I accidentally purchased a 7 speed cassette, rather than the required 8 speed cassette. So rather than immediately buying a new cassette, I put a spacer on so that I could ride with the 7 speed cassette (and this worked rather flawlessly).

However, I got a new cassette today (the correct 8 speed), of the lower end Shimano variety, and I have an interesting problem: while pedaling with any force, it sounds as though the chain wants to shift (a bit jumpy), and I can feel very minor vibrations occasionally. However, the front and rear derailleurs are tuned correctly, and the chain is in fact not trying to shift, it just feels that way.

I think that the problem may be the chain, however I'm not sure. I rode the chain on the 7 speed cassette under 75 miles, so it is essentially new; I just can't figure our why that it is as rough as it is when I pedal.
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Old 06-22-09, 07:48 PM
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Mondoman
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Chad, how do you know the front and rear derailleurs are tuned correctly?
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Old 06-22-09, 07:52 PM
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operator
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Originally Posted by ChadFM View Post
I recently upgraded my (mtb) wheelset, and while doing so I accidentally purchased a 7 speed cassette, rather than the required 8 speed cassette. So rather than immediately buying a new cassette, I put a spacer on so that I could ride with the 7 speed cassette (and this worked rather flawlessly).

However, I got a new cassette today (the correct 8 speed), of the lower end Shimano variety, and I have an interesting problem: while pedaling with any force, it sounds as though the chain wants to shift (a bit jumpy), and I can feel very minor vibrations occasionally. However, the front and rear derailleurs are tuned correctly, and the chain is in fact not trying to shift, it just feels that way.

I think that the problem may be the chain, however I'm not sure. I rode the chain on the 7 speed cassette under 75 miles, so it is essentially new; I just can't figure our why that it is as rough as it is when I pedal.
Assuming you're confident about your F/R Derailleur adjustment skill and you ARE doing it correctly i'd look into a possible bent derailleur hanger. You only rode on the 7 speed cassette for 75 miles. But is it new anyways?
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Old 06-22-09, 08:14 PM
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ChadFM
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Originally Posted by operator View Post
Assuming you're confident about your F/R Derailleur adjustment skill and you ARE doing it correctly i'd look into a possible bent derailleur hanger. You only rode on the 7 speed cassette for 75 miles. But is it new anyways?
Yes, I'm sure that the derailleurs are adjusted correctly.

The seven speed and current eight speed cassettes were both purchased new. I was thinking that the problem might be chain wear, though after such a short lifespan that seems a bit improbable to me. I will check out the rear hangar, that is one thing that I haven't looked at; thanks.

Edit: just checked the rear hanger, and was not bent. I re-checked both of the derailleurs and they are aligned correctly. The only other thing I can think of is to replace the chain.

Last edited by ChadFM; 06-23-09 at 09:36 AM.
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