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  1. #1
    Life is Good
    Reputation: Judd97's Avatar
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    Help me wrap my mind around this...

    Ok folks, here's the situation:

    My buddy's bike is in a state of disrepair. I offered to work on it for him and get it back to running crisp and clean. The main problem with it is it has a frankenstein deal going on with the drivetrain. Here is what he has so far:

    The bike itself is a Trek Alpha 4300... I think a 2000 or 2001.

    Front Derailleur: Shimano SIS topswing 8 speed
    Rear Derailleur: Shimano Acera
    Crankset: Shimano Acera 9 speed (His stock 8-speed crankset broke and he scavenged this one).
    Chain: 8 speed
    Cassette: SRAM 5.0 8 speed
    Shifters: Shimano 8 speed w/ integrated v-brake levers.

    The main problem he's having is the front derailleur will not shift through all three rings on the crankset... presumeably because they are 9 speed rings?

    Anyways, I have a bunch of old 9 speed parts laying around that are in pretty good shape, so I was thinking of swapping them out. Here's what I was thinking of swapping:

    9 speed XT cassette
    New 9 speed chain
    9 speed Shimano LX front derailleur bottom swing
    9 speed Shimano LX rear derailleur

    I also have a pair of Shimano Deore 9 speed shifters, but I do not have any v-brake levers (remember the units on his bike now are the integrated lever/shifters).

    Would the above 9 speed parts work with 8 speed shifters? I assume the shifters won't be able to get through all 9 cogs on the cassette. Would I be better off picking up some cheap v-brake levers and replacing the whole setup to 9 speed?

    Thanks for any help you guys can provide. I hope my post wasn't too confusing
    Get a bicycle. You will not regret it if you live. ~Mark Twain

  2. #2
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    i don't think the 8/9speed thing matters that much on the cranks/front deraileur,i'd look at the many other adjustments and problems that could plague front deraileurs ; close enough to the gear? cable tension? does the front deraileur have play(worn out), is it lined up(parallel) with the chainrings?If there was going to be a problem with 8/9 speed compatability it would be over shifting , the 9 is narrower and the eightspeed shifters /deraileur would move the chain to far and you could reign that in with the adjustment screws.my .02

  3. #3
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    Before you go crazy replacing drivetrain parts, unless they are obviously bent/broken/worn out throw some new cables/housing on and get the derailleus adjusted properly.

    No, the 8 speed shifters will not work with a 9speed casette.

  4. #4
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    The front der. shifting problem may be the result of changing the cranks. Different cranks require different length bb spindles. If the new chain line is outside the front der.'s limits (inner or outer), it won't work.

    Simple solution is to change the bb. You can either look up the crank's bb compatibility or measure to see how far the chain line needs to move.

  5. #5
    Life is Good
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    Quote Originally Posted by slider32
    Before you go crazy replacing drivetrain parts, unless they are obviously bent/broken/worn out throw some new cables/housing on and get the derailleus adjusted properly.

    No, the 8 speed shifters will not work with a 9speed casette.
    I'm definitely going to put some new housing/cables on first and foremost to see if I can dial it in and get it working. I've never really dealt with top pull front derailleurs before but I assume it's not that much different than bottom pull other than how the unit pivots.

    Thanks for the input everyone. Back when I had 8 speed, I didn't do my own work and now that lack of experience is biting me in the butt since I don't know exactly what parts can be interchanged. I didn't think the crankset should make that much of a difference, but it wasn't having shifting problems in the front until he switched them over. I'll head to the LBS tomorrow to get some new cables/housing and give that a shot first.
    Get a bicycle. You will not regret it if you live. ~Mark Twain

  6. #6
    Rub it............
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    Quote Originally Posted by rlouder
    The front der. shifting problem may be the result of changing the cranks. Different cranks require different length bb spindles. If the new chain line is outside the front der.'s limits (inner or outer), it won't work.

    Simple solution is to change the bb. You can either look up the crank's bb compatibility or measure to see how far the chain line needs to move.

    You are partially correct. A front derailleur will work regardless of the chainline. Since MTB's current chainlines are 50mm, then there is zero issue with his current front derailleur. He just needs to adjust the front derailleur limit screws and cable tension to allow the shift to be made properly.

    Difference is BB spindle length is so that the proper chain line will be achieved, but also for chain ring clearance with the frame.

  7. #7
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    check clearence between cranks and chainstays

    Quote Originally Posted by Judd97
    I'm definitely going to put some new housing/cables on first and foremost to see if I can dial it in and get it working. I've never really dealt with top pull front derailleurs before but I assume it's not that much different than bottom pull other than how the unit pivots.

    Thanks for the input everyone. Back when I had 8 speed, I didn't do my own work and now that lack of experience is biting me in the butt since I don't know exactly what parts can be interchanged. I didn't think the crankset should make that much of a difference, but it wasn't having shifting problems in the front until he switched them over. I'll head to the LBS tomorrow to get some new cables/housing and give that a shot first.
    It should be close, maybe not perfect but close to equal. If the drive side has a bigger gap the spindle is long. If the left side has a bigger gap then you can add a spacer to the drive side. I guess we are talking about a threaded bb here.

  8. #8
    meow, meow.
    Reputation: J. Random Psycho's Avatar
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    Quote Originally Posted by slider32
    No, the 8 speed shifters will not work with a 9speed casette.
    Unless a Jtek Engineering Shiftmate (ratio conversion pulley) is used.

    Here's what I done today (heavy snowfalls, no riding, time to work on bikes):



    It's a Saint M810 trigger (9-speed) controlling a Saint M810 derailer over a 8-speed LX HG-70 cassette. It totally works, just need to keep cable/housing a bit cleaner than usual with this setup. )

    PS.
    To operate a 9-speed cassette with a 8-speed shifter, just attach the same 8-to-9 conversion pulley in reverse, it's that simple.

    PPS.
    On the photo, you can see that it's a straight cage Shiftmate, yet there is an 8-to-9 roller inside. Such configuration was not listed on Jtek Engineering web site, but I emailed Ryan and he readily agreed to make me a custom unit. I chose to fit it right next after the trigger, so that it would not multiply any errors in cable movement introduced by housing imperfections.

    You can also see that in order to place the unit where it is, I had to file down some 2.5 mm off the trigger's adjuster barrel, so as to get full adjustment range from it. This is because of a clearance issue between Shiftmate cage and barrel body (gold piece). I also slightly sanded down one end of the Shiftmate barrel piece, so that it would fit into housing receptacle on the barrel.

    Also in the news: I got some riding time on this setup, and it works flawlessly!
    I'm totally digging the 810 trigger, too.
    Last edited by J. Random Psycho; 12-18-2010 at 04:34 PM.
    26" faithful.

  9. #9
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    Thanks for all the advice, everyone. After a little bit of fussing I think I got it. I put new cables through and don't quite have it dialed in yet, but I at least got the front derailleur to shift into the big ring smoothly (it wouldn't reach it before) by fiddling with the limit screws. I'm not sure why the change was so sudden and drastic; prior to changing out the cranksets, it was supposedly fine but after putting the new one on (by the way, this is a square-taper, threaded bb) I guess it wouldn't reach the large ring.

    Thanks for the info guys! It'll be nice to return this bike and have it running like new for him... maybe I'll get a riding partner back!
    Get a bicycle. You will not regret it if you live. ~Mark Twain

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