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  1. #1
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    pulse while pedaling w/ new cassette and chain

    I just installed a new PG850 cassette (11-32) and a pc870 (7/8 spd) chain on my bike. It has just a single chainring. All shifting is fine through the gears, however, in the 7th gear (12t I believe) there is a noticeable pulse while pedaling. all other gears are smooth. I check the derailleur alignment and adjustment, but no change. It seems like the chain situates itself very close to the 11t sprocket while engaged on the 12t and possibly contacting is ever so slightly, possibly causing the pulse? Has anyone has a similar issue? I've never had any issues with this before. Do they just need to break in? will a narrower 9spd chain fit?
    Sette Ace
    Mongoose IBOC Zero-G SX (SS road machine)

  2. #2
    ~Disc~Golf~
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    look for a stiff link in the chain (pedal backwards while on the stand or upside-down.
    if that's not the case, look for a burred/bent tooth on the 12T cog.

    then I'd check for a bent hanger...or maybe I'd check that first - I dunno

    *TIP* a stiff link will be noticable at a predictable position in your pedal stroke - ESP w/ 1 ChainRing
    Honestly, you just take a deep breath and say Fuck it.

  3. #3
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    I've got the same problem, on the same cassette, same gear/cog. I was just trying to sort it out today with no luck. I thought maybe I had the b-screw set too close to the cog but it's not. It's definitely not a stiff link in the chain because the pulse has too high of a frequency. You can't feel it when you spin the chain backwards but under power it's very noticeable.

    Anybody have any other ideas?

  4. #4
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    I agree. There is no stiff link in the chain. I adjusted the b-adjustment as well, but no change. I thought maybe the chain was contacting the cog next to it, but after some inspection determined that there is clearance. The pulse frequency is very short, consistent, and constant, leading me to believe it is how the chain is meshing with the gear. Perhaps there is a production issue with this model or batch.
    Sette Ace
    Mongoose IBOC Zero-G SX (SS road machine)

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