CARTRIDGE BOTTOM BRACKET
(BB) REPLACEMENT

Bottom brackets used to be one of the biggest replacement hassles, but thanks to the proliferation of cartridge bottom bracket units (first introduced by Sun Tour in 1986, and now as standard equipment – mostly Shimano – on virtually all bikes above R2,000), it’s a relatively simple process.  It’s also a great upgrade, as a better bottom bracket spins more smoothly and, depending on the axle material, can save you several grams of weight.

Several special tools are needed to replace today’s cartridge bottom bracket, but ones you should have anyway if you’re going to get serious about servicing your bike.  Here’s a list of what you’ll need (also needed in the event you’ll be servicing/replacing your crank):

• 14/15mm socket/crank bolt tool (Park), OR, 8mm long-handle Allen key

• Crank puller (Park)

• Splined cartridge tool (Shimano or Park), OR, spanner tool (separate cup-style cartridge)

• Adjustable (crescent) wrench

 This procedure is best performed in a bike stand.  Otherwise, you may need assistance from a friend to hold the bike steady as you loosen (and tighten) the bottom bracket cups.

First, lift the chain off the chain rings entirely and let it rest on the bottom bracket shell.  Remove the crank bolts with either the 14/15mm crank tool or 8mm Allen key.  On cranks that have bolts (or nuts), you may need to remove the dust caps to expose the bolts / nuts.

Next, with the push-bar of the crank puller threaded all the way out, thread the crank puller’s threaded cuff into the crank’s bolt-hole until it has gone at least half way.  Begin turning the push-bar handle clockwise until it begins to resist.  Hold the crank arm at nine o’clock and the wrench at three o’clock and thread the push-bar handle in until you can wiggle the crank off the spindle (it will be very hard to push the push-bar initially).  Repeat for the other crank arm.

On current Shimano cartridge bottom brackets, the right adjuster cap is actually part of the cartridge, not separate like the left cup (looking down onto the bottom bracket as if you were on the bike).  This design makes it very easy to remove and install as there is only one cup to actually adjust.  You just thread the cartridge in or out from the right, then the left adjuster cup.

To remove the bottom bracket, first loosen the left adjuster cup with the splined bottom bracket tool (clockwise left-hand thread).  Next, remove the cartridge from the right side of the bottom bracket shell (clockwise, standard thread).

Clean the threads of the bottom bracket shell, then apply some clean bicycle grease to the threads.  If you are installing a cartridge bottom bracket with separate left and right cups, install the right cup first.  Thread the cup into the shell (clockwise) until the outer surface of the cup is flush with the edge of the bottom bracket shell.  Install the cartridge from the left side, then install the left cup and tighten securely.  This design allows you to fine-tune the spindle position for more precise chain-line alignment.

However, if you are installing a Shimano or similar unit that has a fixed right cup, simply thread the entire unit into the bottom bracket shell until the flange tightens down against the shell.  Tighten securely.

Next, take the left side cup and thread it into the bottom bracket shell.  Tighten all the way until snug.  Replace crank arms and tighten bolts.