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Bottom Bracket How To

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Bottom Bracket How To

Old 06-05-11, 07:21 PM
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Bottom Bracket How To

I want to replace an old school Stronglight 99 crank and bottom bracket with a modern compact crank and bottom bracket. I don't understand the cartridge bottom brackets. From what I've seen, there are pre-assembled bearing and spindle set ups. Some have the spindle, some do not. How do those get threaded onto the frame? How does the spindle get assembled? Do the cranks attach with the same bolt on method, and remove using crank pullers as previously, or is there some other method? By the way, the frame has Italian threads.

Once I understand the assembly method, I can figure out what I need to buy. One concern I have is that my chain line seems sensitive. The spindle needs to be long enough on the RHS so that the chain rings clear the chain stay.

THank you,
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Old 06-06-11, 06:12 PM
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The modern bearing cups - whether internal or external, use the same threads as you already have, so just buy a BB with Italian threads.

I believe that internal type units can come in different spindle lengths. I know that Shimano makes different internal units depending on double or triple, etc. I've never dealt with ISIS or square taper sealed units, but I believe there are spindle length options.

The external type come with spindles already attached to drive side crank arm; I have no idea if there's spindle length options. If there are, I'm unaware.

Take a look at the Park Tool website for BB and/or Crank installation and removal to get specific instructions including the tools you'll need.

Probably the only new tool you'll need is a BB tool for the type of BB you're using (see Park Tool installation guide). They are available in almost any LBS or online bike shop for as cheap or expensive as you want (consumer vs. pro-grade tools). I'll assume you already have hex-key wrenches and maybe a torque wrench if you believe in them.

For removal, you will probably need a crank puller for the internal type (ISIS or Octalink). This might be different from the one you've been using for square taper cranks. Mine works for both. Most external types don't require a puller.

Last edited by Camilo; 06-06-11 at 06:51 PM.
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