Updating older bottom brackets
We will talk about other types of bottom bracket-crank arm interfaces later in the article.The Birth of the Cartridge Recently, the loose-bearing system is largely being phased out in favor of another system, known as the cartridge bottom bracket.Ever get confused by all the bottom bracket “standards” out there? Connecting the left and right cranks, this is one of those important elements on the bike that directly effects power transfer between the rider’s legs and the bike’s drivetrain.
Loose Bearing Bottom Brackets Before the 1990’s, loose bearing bottom brackets were the standard on almost any bike purchased outside a department store, and still are for some lower to mid-range bikes.
The two interfaces are remarkably close in dimensions, but the ISO design tapers down to a slightly smaller end.
Logically enough, most European brands (Campagnolo, etc) adapted the ISO interface and Asian brands (Shimano, Sugino, etc) stuck with the JIS interface.
In order for a bottom bracket to screw into a frame’s shell, its threading must match perfectly with the shell, so check the threading of your frame before ordering a new bottom bracket.
You local bike shop will be able to tell you what type of threading and bottom bracket shell diameter your frame has if you don’t know.