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  1. #1
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    idrive, chain rubs eccentric when its on granny

    i cant say that i ever noticed this before, but i was just adjusting the front derailleur and i could feel the chain rubbing on something. i took a closer look and the chain is brushing up against the eccentric when its in the granny gear. I have absolutely no idea how long its been doing that, but this is at least the first time ive heard it.

    any quick fix options? spindle too short? sorry i dont have any pictures, but let me know if you have a diagnosis for me. ill probably stop by the lbs by the end of the week if i cant figure it out. I've never replaced a bb myself, always took it to the LBS. w/ the right tools, is it an easy job? how do i know what spindle length i should have on there?

    RF next Lp
    2001? gt i drive

    thanks in advance
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  2. #2
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    I always had a longer BB on my i-drive than most people had. I think i had it up to 118...

    Longer BB should solve the problem, it has probably been doing it the whole time and you just didn't realize it.

    BB replacing is one of the easier bike jobs if it's the older style cartridge versions which is sounds like it is. If it's a newer model with the bearings on the outside it's a little tougher.

    If it's internal you need a crank puller and the bb removal tool. That's it, simple job. Plus it's good to know what size BB you have for future reference. My first I-Drive bb was 73x113 if i'm not mistaken...

  3. #3
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    If it's internal you need a crank puller and the bb removal tool. That's it, simple job. Plus it's good to know what size BB you have for future reference. My first I-Drive bb was 73x113 if i'm not mistaken...[/QUOTE]


    Am i going to run into any problems running a longer spindle? I'm going to take it off this week and see whats actually in there, just ordered some new tools. until now i've left all bb and crank repairs to the LBS. I did some looking, pricepoint, jenson.... there isnt much left in the square taper bb selection. any suggestions. i was specifically looking for shimano's un73. didnt have much luck in the 73/118 area. i wont buy anything until i see what size is installed right now. (i dont have a ruler w/ mm measurement.. wallmart next in line)
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  4. #4
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    Quote Originally Posted by laackund
    If it's internal you need a crank puller and the bb removal tool. That's it, simple job. Plus it's good to know what size BB you have for future reference. My first I-Drive bb was 73x113 if i'm not mistaken...

    Am i going to run into any problems running a longer spindle? I'm going to take it off this week and see whats actually in there, just ordered some new tools. until now i've left all bb and crank repairs to the LBS. I did some looking, pricepoint, jenson.... there isnt much left in the square taper bb selection. any suggestions. i was specifically looking for shimano's un73. didnt have much luck in the 73/118 area. i wont buy anything until i see what size is installed right now. (i dont have a ruler w/ mm measurement.. wallmart next in line)[/QUOTE]

    what is it rubbing, Im not familiar with the eccentric?
    if its on the drive side a longer BB might cause more issues, the middle ring to center of the BB shell needs to be 50mm, if you move it out it wont shift right

  5. #5
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    what is it rubbing, Im not familiar with the eccentric?
    if its on the drive side a longer BB might cause more issues, the middle ring to center of the BB shell needs to be 50mm, if you move it out it wont shift right[/QUOTE]


    I'll have to pick up a ruler tonight then. i dont have a digitial camera, but the pic of the round thing is the eccentric. the other pic is just the model i drive, but not mine... the eccentric is pressed into the the BBshell. its not flush with the edge of the shell, sticks out by about .5 mm. anyway, when the chain is on the 22t ring it brushes against it just enough to create some resistance only noticable by hand.
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    1 hockey puck-$2
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  6. #6
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    I should have mentioned that yes you will probably have to tweak your setup a little bit by installing a longer BB. If you only go up a little bit it should be ok but if you go from 113 to 118 you can expect it to act funny because your chain is now 5mm farther out than it used to be. Minor tweaking.

    Yeah square taper is becoming harder and harder to find. Keep searching or upgrade the cranks/bb to some other type of connection. I realize outer-bearings are a bit expensive still but honestly for the price of new cranks and a new bb, it's not that much more.

    If all else fails take it to the shop and let them fix it some other way, but this is the only way I can think of. If it's rubbing against the eccentric it's pretty damn close. The bb replacement is the cheapest solution, but you could use a different crank that's farther out, you could use a smaller (width) chain, etc...Plenty of options they could offer but a longer bb is cheaper and faster...

  7. #7
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    Only 2.5mm Difference

    Quote Originally Posted by Purogamer
    I should have mentioned that yes you will probably have to tweak your setup a little bit by installing a longer BB. If you only go up a little bit it should be ok but if you go from 113 to 118 you can expect it to act funny because your chain is now 5mm farther out than it used to be. Minor tweaking.
    The chainrings will only be shifter out by 2.5mm....each end of the spindle is 2.5mm longer.
    This may or may not be an issue at all. There are 2 commonly accepted chainlines, 47.5mm and 50mm. If your current setup is 47.5mm moving out to 50mm won't be a problem. You'll just have to adjust the limit screws of the derailleur.
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