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Tapered Splined Crank Removal and Replacement
Because this type of crank attachment is often part of an integrated
crank-bottom bracket set, there may be several variations. The crank has slots
around a round opening, but the fitting is tapered so the cap bolt cinches it
tight. The slots fit onto teeth that stick out from a hollow
round spindle in the bottom bracket. You need a special
crank-pulling tool. Often, the tool is specific to the bottom bracket of the
bike. If you have the right tool for your bottom bracket, remove the cap
and use the crank-puller tool (see below). If you don't don't have the correct
tool, here's how to do it in an emergency with a standard crank-pulling tool. Other crank types: standard
female-threaded tapered spindle, male-threaded spindle
with nut, untapered splined spindle.
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Shift the front derailleur into the smallest chainring. Pull
the chain off the ring and lay it on the round part of the frame that
surrounds the bottom bracket.
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Hold the pedal and use a large 15 mm hex wrench to remove
the cap bolt. Counter-clockwise! (Righty-tighty, lefty-loosy) |
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Remove the cap bolt. If the bottom bracket is the
non-tapered splined variety, the crank will simply fall away. If you have
the tapered type, the crank remains firmly locked in place.
If you have the correct crank-pulling tool for the bottom bracket, this
is where you use it.
If you find yourself making an emergency repair, and your toolbox
contains old crank-pulling tools -- none of which fit -- here's the method. It's not sanctioned by
any manufacturer, so if you break something, tough patooties. |
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Get a hardwood dowel, or whittle an approximately-round bit
of very hard wood to fit inside the hollow area in the bottom bracket.
Make it long enough that, when it's inside the BB and pressed against the opposite (non-removed)
cap bolt, the outer end touches but doesn't go beyond the innermost threads inside the BB, or
flush with the "shelf" where the hollow part of the BB gets
smaller.
Find hard washers that are approximately the size of the dowel's
diameter, and have holes too small for the crank-pulling tool to slip
through. |
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Put some sticky stuff on the dowel so the washers stay put
on the ends.
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Insert the dowel into the hollow of the bottom bracket. |
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It should sit just inside the second (smaller) set of
threads, or even with the "shelf" where the BB hole becomes
smaller diameter if you don't see two sets of threads. |
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Get your old generic crank-puller. If you have more than
one, select the one with the largest-diameter core (so a larger area will
be pushing on the washer and dowel).
Turn the center piece of the crank-puller so the
"pushing rod" part comes back close to the larger
(outward-facing) threads.
Thread your crank-pulling tool into the threads on the inside of the crank. |
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Now begin turning the central part of the pulling tool so
the pushing ram goes into the bike.
The idea is, it will hit the washer and dowel and push against it.
Because the tool is threaded into the crank, this shoves the crank and the
pulling tool away from the bottom bracket's teeth. |
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After a few turns the crank should drop away easily. If it
doesn't, your tool may be mashing up the wood inside the BB. Remove the
tool and take a look.
Well, the crank is gone. Tip the bike so the wood and washers fall out.
If the wood doesn't fall out, it may be stressed or cracked so it's
jammed inside the BB. Now, how do we get the dowel out? |
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Take the cap out of the opposite crank.
Leave the crank there. You just need to have a hole where you can see
the other end of the dowel. |
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You now have a tunnel through the BB. Push the dowel and
washers out from either side.
Here I'm using a long hex wrench to push the dowel.
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Make sure you got both washers out, and that there are no
bits of wood on the threads. |
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Now, do the project for which you removed the crank (such
as chainring replacement.) |
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Done with your work (bottom bracket replaced, chainrings
replaced, new cranks put on)?
Put the power-side crank back on. If you replaced chainrings, make sure the power-side crank sits
over the raised metal position indicator on the large chain-ring. Use the cap bolt to tighten
the crank onto the splines.
Replace the cap bolt on the opposite side, if you removed it. The
opposite-side crank should be 180-degrees from the power-side crank. |
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