This go ’round we’re going to take a look at adjusting a loose bottom bracket. This usually only pertains to the old type serviceable bottom brackets. Lets take a look at some bottom brackets to help you identify the different types out there.

Cartridge type bottom brackets are typically not adjustable.

The cartridge type bottom bracket is a modular piece that contains the bearings and spindle all in one enclosed unit. The spindle can be of various types. The square taper, (Seen above), the Octalink type splined spindle, or the ISIS type splined spindle. Most of these units have some sort of toothed or splined interface to remove them by. These bottom brackets are not serviceable.

Most recently, two piece cranks with outboard bearings have hit the scene.

Outboard bearing bottom brackets are easily identified by the two piece crank, large pipe spindle that sometimes you can look through, and the bearing cups which are out side the frame. These and the offshoot BB30, BB90 bottom brackets are not adjustable.

A serviceable bottom bracket.

This is a serviceable bottom bracket. Most always a square taper spindle with the outer lock ring and the cup on the non-drive side having some sort of interface for a specific tool used to turn the cup in or out of the bottom bracket shell. In our example, it is a pin spanner wrench that will interface here. Some more commonly found examples will have round “holes” that a pin spanner will work with. Sometimes a special spanner wrench is required. Either way, the adjustment process is the same.

The lock ring spanner shown on the lock ring.

The adjustment procedure is not unlike that of a head set adjustment. There is a locking component and an adjusting component to the bottom bracket and headset which are adjusted similarly. Here I am showing the alignment of the lock ring spanner on the lock ring that will yeild the best leverage. Remember, turn left to loosen here.

Adjusting the bottom bracket with a pin spanner.

Just as in our headset example, you only need to back off the lock ring slightly. Then using the properly interfacing adjustment tool, you can tighten the adjustable cup a degree, maybe two. Not much now! Holding your adjustment with your spanner, take the lock ring tool and tighten it back up. (If you fail to hold the adjusting cup stationary, it may actually turn with the lockn ring and over tighten the bearings.) Check for any looseness in the system by grabbing each crank arm and try to rock the arms side to side. If you feel a knock or any lateral movement, then you may need to go through the adjusting procedure again. (Make sure your crank arms are tight! If they are not, you’ll get a false reading.) It may take a few times of going through the procedure before satisfactory adjustment is reached.

The threadless head set adjustment post is coming!