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  1. #1
    Senior Member
    Join Date
    Apr 2005
    Billings, Montana
    My Bikes
    Trek 2100, Trek 960, Trek 2300, Novara Randonee, Specialized Langster
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    ready to change out chainring, but...

    Based on advice given here, I decided to change a 30t chainring for a 24t to get some lower gears. I just received the chainring, but before I dive into removing the crank and chainring, I have a few questions concerning this Octalink bottom bracket and crank.

    1. Do I need any special tools? I can see an allen bolt which looks like 10mm. i can get a wrench at the local hardware store. Anything I should be aware of?

    2. I have an old crank removal tool from twenty years ago. will that work or will I have to buy something new? If the latter, what?

    3. After the crank is off, I will unbolt the inner chainring and replace with 24t. anything I should be aware of?

    4. Will I have to move/adjust the front derailleur or replace it?

    5. Anything else I should know about.

    Thanks for the help.
    Trek 2300
    Trek 2100

  2. #2
    coprolite fietsbob's Avatar
    Join Date
    Jun 2010
    NW,Oregon Coast
    My Bikes
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    Hardware stores have Metric allen wrenches I have an 8mm allen as my crank arm fixing bolt,
    but I cannot see yours.

    The Octalink is a bigger tube than the square taper , you need a new crank arm extractor tool.

    IF there are 2 little pin spanner holes in a ring around the bolt head

    you may have a self extracting bolt . the ring screws into the place where the extractor may
    be threaded into , It should come out with out another tool..

    [carefull I've had a self extractor strip the crankarm and not budge ]

    If there is a black plastic ring around the bolt Its not self extracting..

    You should not have to remove the FD.
    if you are not changing the big ring..

    you will need a 5mm allen to take off the third ring mounting bolts.
    Last edited by fietsbob; 09-28-10 at 12:28 PM.

  3. #3
    John Wayne Toilet Paper nhluhr's Avatar
    Join Date
    Feb 2006
    My Bikes
    BH carbon, Ritchey steel, Kona aluminum
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    There is a tool made by shimano that is used to screw in those self-extractor nuts AND to hold chainring nuts. It makes it a lot easier to work on cranks but you can get by without it.

    Shimano TL-FC21

    Self-Extractor Crank Bolt:

    Non-self-extracting bolt:

    If you have and will use the self-extractor function, make sure the nut is screwed all the way into the crank-arm before you start unscrewing the bolt, or else the lack of thread engagement in the arm may strip the self-extractor out of the arm and damage threads on one or the other. When you put it back together, clean and re-grease all the surfaces that will touch inside. Make sure you tighten the self-extractor down all the way (with the washer in between) after you tighten the crank bolt.

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