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  1. #1
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    EBB newb questions

    I am new to S and i think my chain might be a little bit loose. How do i know what a good chain tension is? Also i have a Truvativ GXP External Bearing EBB and have no idea how to adjust it. Can someone please help a newb out?

  2. #2
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    an externall BB end a an EBB are two different things. does your frame have the eccentric shell? What type of EBB is it? pinch bolt, set screw or expanding wedge?
    Quote Originally Posted by thefuzzbl
    aluminium has a tendency to fail when you need it most. i.e. you end up with a bad day.

  3. #3
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    wow this all sounds foreign to me. If by set screw you nean a bolt under the shell of the BB then yes it has a set screw.

  4. #4
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    Quote Originally Posted by The Diesel
    wow this all sounds foreign to me. If by set screw you nean a bolt under the shell of the BB then yes it has a set screw.
    There should be 2 screws on the shell. If so, you have a "set screw" EBB. If they are actually 2 bolts and the shell is split from side to side, then you have a "pinch bolt" EBB.

    Why don't you just tell us what the frame is?

    Anyway, loosen whatever is keeping the BB tight, then rotate the whole EBB forward to remove excess chain slack. Just take the slack out though, you don't want to have the chain get tight anywhere as you turn the cranks.

  5. #5
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    Oh yeah, EBB stands for Eccentric Bottom Bracket, and not external bottom bracket which is what your cranks use. Confusing? Yeah I can see that.

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    Quote Originally Posted by Wish I Were Riding
    There should be 2 screws on the shell. If so, you have a "set screw" EBB. If they are actually 2 bolts and the shell is split from side to side, then you have a "pinch bolt" EBB.

    Why don't you just tell us what the frame is?

    Anyway, loosen whatever is keeping the BB tight, then rotate the whole EBB forward to remove excess chain slack. Just take the slack out though, you don't want to have the chain get tight anywhere as you turn the cranks.
    Its an 08 Raleigh XXIX. There are 2 allen head bolts but the shell is one piece. So loosen the bolts and thenrotate the EBB how? by turning the cranks? And i understand removing the slack but what do you mean i dont want the chain to get tight anywhere as i turn the cranks? What would make it get tight?

  7. #7
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    Go to a local bikeshop and let them do the adjusting.

    No offence but your remarks sound like you're not too accustomed to using tools and equipment. Better bring the bike to a shop and maybe they can give you some hands on instruction.

  8. #8
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    Quote Originally Posted by DiDaDunlop
    Go to a local bikeshop and let them do the adjusting.

    No offence but your remarks sound like you're not too accustomed to using tools and equipment. Better bring the bike to a shop and maybe they can give you some hands on instruction.
    Lol. Not too accustomed to using tools? I'm a Nissan tech and also have and airframe and powerplant license to work on aircraft. I might not be the best there is but I can hold my own in a shop. This doesn't mean I know the first think about a bike, and that's why I am here. A bike might seem very basic to someone with more experience but its totally new to me. Naturally I like to fully understand something befor I dig into it. I probably will have my shop show me, but you shouldn't go around making assumptions about people you know nothing about.

  9. #9
    meatier showers
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    Sounds like your crank is an external bearing unit, and that your frame has an eccentric bottom bracket.

    The 'shell' is the part that's the frame and the 'eccentric' is the part that rotates within the shell to adjust chain tension.

    In order to adjust my eccentric, first I loosen the bolts that hold the eccentric in place. My eccentric has a hole drilled through the end (non drive side) parallel to the length of the shell. I stick my 5mm allen wrench into this hole (not very far as I want much of the allen wrench to stick out). Then I rotate the arm of the crank up against the allen wrench and continue to rotate the crank, which will now force the eccentric to rotate with the crank. When the chain tension is correct, I pull the allen wrench out and tighten the shell bolts.

    There are several type of eccentrics and I'm not sure yours is the same as mine, but anyway this is how I do it.

    Good luck.

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  10. #10
    human dehumidifier
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    Quote Originally Posted by The Diesel
    What would make it get tight?
    Chain ring or cog that isn't perfectly round, or not centered perfectly. Visualize it and it'll be clear.

    BTW, how come mechanics are called techs now? Us old time guys would've already taken that bike completely apart at least twice.
    I Just Wasn't Made For These Times

  11. #11
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    Quote Originally Posted by The Diesel
    What would make it get tight?
    If you continue to rotate the EBB forward, the chain will tighten to the point where you can't rotate the EBB any more forward. That would be too tight. You want a little slack, but no so much that your chain visually droops. Also, a non-perfect chainring or cog can make the chain tension vary as the cranks are turned, which can be confounding unless you know the cause. If its bad, I believe replacement of the offending ring is the only fix.

    As for rotating the EBB, flip the bike upside down, loosen the EBB bolts, grab the external bearing cups in each hand and carefully rotate the EBB to the desire position and chain tension. After making sure you didn't accidentally move the EBB left or right, tighten the bolts, then check tension again.
    ride natty ride

  12. #12
    Sweep the leg!
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    Quote Originally Posted by The Diesel
    I'm a Nissan tech and also have and airframe and powerplant license to work on aircraft.

    you're not touching any of my vehicles if you can't figure out a XXIX's EBB.
    Authorities speculate that speed may have been a factor. They are also holding gravity and inertia for questioning.

  13. #13
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    Quote Originally Posted by Caffeine Powered
    you're not touching any of my vehicles if you can't figure out a XXIX's EBB.
    I havent touched it at all. I hardly glanced at it to see if it had bolts or screws. I can figure it out on my own but I thought id figure out how it works befor i messed it. I figured i could come here and get a few pointers. ****, do you have to ack like a dick to make yourself feel like a better more experienced rider/bike mechanic? I realize an EBB is a very basic component and i knew my question was a newb question, and i even expected a little criticism but damn.

  14. #14
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    I just adjusted it and now realize where you guys were coming from. Its amazingle simple, i just thought there was more to it. I tightened the 2 bolts pretty tight, i hope i dont hear any noise or have any issues with it. It doesnt seem like a very good design, althought i do like the simplicity.

  15. #15
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    Quote Originally Posted by The Diesel
    Lol. Not too accustomed to using tools? I'm a Nissan tech and also have and airframe and powerplant license to work on aircraft. I might not be the best there is but I can hold my own in a shop. This doesn't mean I know the first think about a bike, and that's why I am here. A bike might seem very basic to someone with more experience but its totally new to me. Naturally I like to fully understand something befor I dig into it. I probably will have my shop show me, but you shouldn't go around making assumptions about people you know nothing about.

    I make assumptions from what I read. And what I read is that you were very afraid to take it apart. Most people that are afraid or reluctant to take mechanical things apart are not that informed/schooled. It's better for them to go to a shop and get on hands education instead of trying to understand instructions from an internet forum. And maybe screwing things up beyond repair.

    Sorry if I have underestimated your technical abilities. But hey it's the internet. There are loads of sites that explain how EBB's work.

  16. #16
    Sweep the leg!
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    I know I'm a d!ck, but as a licensed mechanic and electrician I'm not afraid to take things apart to discover how things work. but on occasion, if they're available, and nobody's looking, I read the owner's manual.

    Happy reading.
    Last edited by Caffeine Powered; 03-04-2009 at 06:13 AM.
    Authorities speculate that speed may have been a factor. They are also holding gravity and inertia for questioning.

  17. #17
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    Im not scared of taking it apart. Im scared of missing a day of riding cause i screwed it up and had to take it to the shop lol. It would piss me off if i couldnt ride for 1 day because of something i screwed up. But, the chain is tight so all is good. Thanks for the help and criticism guys, it made for a fun thread.

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