Some axles have flanges between the bearings (DT Swiss is a good example). In this case, smack the end of the axle to drive the bearing out, using a socket of the right size against the end of the axle to protect it. Smack it the other way to knock out the other bearing.
Driving the bearing out of a bottom
bracket up using Enduro's
external bearing press/puller.
By tightening the bolt, you push the
collet expander (B - see image below)
against the collet (A) that
is expanded inside the bearing.
On a DT rear hub, you can get the non-drive bearing out this way, but you cannot remove the drive-side bearing without first unscrewing the radial teeth from the hub that engage the freehub star ratchets. This requires a special DT tool held in a very solid vise.
Driving the bearing(s) out of the freehub body, once removed from the hub, is often simple with an appropriate diameter hex key.
First, remove the crankarms. On outboard-bearing bottom brackets other than Campagnolo, the bearing is pressed inside of the outboard ("external") cup. Unscrew the cups from the frame with the proper tool. Remember: the drive-side cup will be left-hand threaded unless it is an Italian-made frame.
You will now need a specialty tool for removing the bearings from the external bearing cups. Enduro has a nice one (made by Sonny's Bike Tools), and Phil Wood also makes such a tool.
You can first remove the bearing cover seals (I mean the ones covering the face of the outboard cup, not the actual seals on the cartridge bearings), or you can leave them on, and when you push out the bearings in the tool, the bearings will push the cover seals off. To remove a cover seal, slip a razor blade under the edge and pry it up, possibly working around the outside with a thin screwdriver blade for FSA and Shimano cover seals that extend inside the bearing bore.
The key to the external bottom bracket bearing puller (Figure 2) is a two-piece collet (A below) with a band around it. You drop the collet down into the bearing from the inboard side and push a rounded-nose cylindrical "collet expander" (B below) into it to spread it inside the bearing bore. The lips of the collet will catch the back of the inner bearing race. Many bearing cups have an internal shelf that would prevent you from being able to push the bearing out if you did not have this collet.
Photos: Brad Kaminski/VeloNews
Once the collet and collet expander are in place, put the bearing cup outboard-end face down into the tool's cup holder and push the bearing out by applying pressure on the collet expander; in the Enduro tool you accomplish this by running a big bolt through it and tightening it.
This often takes considerable force, and especially in the case of TruVativ/SRAM GXP, the bearing finally comes free with a loud pop.