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  1. #1
    xls
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    Eduardo Naranja
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    New question here. Chainsuck after 8-spd to 9spd conversion?

    I've read the excellent chainsuck analysis on http://www.fagan.co.za/Bikes/Csuck/OVERALL.htm and I'm trying to apply this to my bike.

    I bought a used Epic with 8-spd shifters, and converted to 9-spd: SRAM PC99 chain, SRAM rear sprocket (forgot which), SRAM rocket shifters. XT front and rear derailleur. The bike shifts really well except for the occasional chainsuck when I shift into the granny ring.

    The rings aren't worn at all, that was the first thing I checked. I will have a close look tonight to see if there is maybe one bent tooth or something. I haven't ridden it enough with the 8-spd setup to tell is there was chainsuck or not but I don't recall any (it's been ~6 months).

    I'm not sure about the chainrings that are on the bike. The crank is a strongarm 1 and the largest chain ring says "7075 four millimeter" on it, ok I guess that's 7075 Aluminum and the ring is 4 mm thick. On the inside, all rings have a print on it: small - "heat-treated CrMo, 22-V2-2000", middle - "32-V3H-2000", large - "44-V2-2000".

    Does anyone have an idea if these are maybe not compatible with a 9-spd chain?

  2. #2
    Wizard of the Trail
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    I am not sure if I am right here, but if the chainrings are 8 speed and you are running a 9 speed chain, that is your problem. I believe the rings on an 8 speed is wider than a nine. Try different rings that are 9 speed specific to see if it goes away. You can run 9 speed rings on a 8 speed drive, but not the other way around.
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  3. #3
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    If you have a new chain and cassette and you still have chain suck, chances are the rings are causing the problem, even if they look OK. I run 8 speed rings with 9 speed chain and have no problem.

    Wombat

  4. #4
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    When you say you're shifting into the granny when you get chainsuck, is it the granny ring it's wrapping on? Or the middle ring? What rear cogs are you in when this happens the most? Even though you haven't seemingly changed the crank/rings, have you checked your chainline?
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  5. #5
    xls
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    Eduardo Naranja
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    Thanks all for your replies. I'm not sure whether the chainrings are 9-spd compatible or not. I guess I will just have to try a different set.

    When you say you're shifting into the granny when you get chainsuck, is it the granny ring it's wrapping on? Or the middle ring? What rear cogs are you in when this happens the most? Even though you haven't seemingly changed the crank/rings, have you checked your chainline?
    It's wrapping on the granny ring, when/right after shifting to it from the middle ring. I don't recall exactly what the rear cogs were, but quite possibly some smaller ones (away from the hub), maybe cog #5 or so (1 being the one closest to the hub).

    As for the chainline, in my layman's opinion it looks pretty straight. What I did was to shift into middle ring in the front, middle cog in the rear and then peer down the chainline from the front of the bike. I shifted a few times to see how the chain behaves and it looked very straight in those gears. Is there a better / more precise way to check the chainline?

    It's a weird problem, I guess. I'm very happy with the bike and how it shifts otherwise (tinkered with it a *lot*) and chainsuck, well... sucks.

    I will try different chainrings hopefully this weekend. If I find anything interesting, I will post the results. Thanks again!

  6. #6
    xls
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    Eduardo Naranja
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    So I tried flipping the granny ring (so it rotates the other way). That affected the tooth offets between the middle and the granny ring (neither ring shows any wear, so that isn't affected) but it had no effect on the chainsuck. Next step was a new granny ring (different make, same size), also no change. Chainsuck is still there badly. I'm starting to get really frustrated over this.

    A couple of questions:

    1)
    Is my shifting / pedalling technique bad? I have not had these problems with my previous bikes. The way I shift / pedal when going from middle to granny is like this: *No force* when pedaling, just keep rotating the chainrings and shift. Once a part of the chain is off the middle ring and hooked on the granny I start pedaling with quite a bit more force(*) (but not full-on mash it) to keep me going. When the chain is completely off the granny ring, I pedal with full force again.
    (*) If I don't do that and instead keep rotating the chainrings, the shifting is fine. Is this my mistake? I don't recall having to do that on my older bikes (stumpy pro, and an older lower-end GT, both triple in the front).

    2)
    Should I just buy a complete new set of chainrings? Or just a middle ring? Given the cost of a whole set of chainrings, I'm thinking I might as well get a whole new crank, maybe an XT octalink. I have Specialized Strongarm I (I think they're a bit stiffer than Strongarm II), now.

    Again, chain and rear cassette is pretty much brand new (maybe 100 miles or so). Only bad thing for the chain is numerous chainsuck events (~20).

    Any ideas?

  7. #7
    xls
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    Eduardo Naranja
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    Anyone? Bueller?

  8. #8
    xls
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    Eduardo Naranja
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    Just a short update in case anyone is reading this. I rotate the granny ring by 90 degrees, and that actually helped the problem to a degree where I can live with it. I still get chainsuck every now and then but not as often anymore (~30% of what I had before). For now I will just live with it and see if I can learn to minimize it (eg. shifting at a specific pedal position, etc).

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