Both standards are designed to use a crank arm spindle with a 30mm diameter (hence the ’30’ in the name), but with a BB30 set up the bearings sit directly in the frame, and with a PF30 the bearings are housed in a nylon or aluminum retainer that gets pressed into the frame. Tolerances need to be tighter with a BB30, making this a more expensive system to manufacture. BB30 was originally developed by Cannondale in 2000, but they have since made the dimensions and technical drawing available to any company who would like to use the BB30 standard. To make things more confusing, several companies are now offering cranks with 30mm spindles that work with the BB92 standard – by using a bearing without a retaining cup, an inner race that’s wide enough to accommodate the larger spindle can be used.
What is the difference between BB30A and BB30
The BB30a is similar to the BB30 standard, but the frame BB shell is 5mm wider on the non-drive side. BB30a system uses thin spacers and/or a wave washer between the bearings and the crank arms to take up any slack and micro-adjust the chainline of the crank.
What is the difference between PF30A and PF30
PF30a frame shell inner diameter is 46mm. The PF30a is similar to the PF30 standard, but the frame BB shell is 5mm wider on the non-drive side. PF30a system uses thin spacers and/or a wave washer between the bearings and the crank arms to take up any slack and micro-adjust the chainline of the crank.
BB30 frame shell inner diameter is 42mm, has two bearing retaining clips and two 6806 bearings pressed directly in the frame. PressFit-30 (PF30) bottom brackets are a separate component pressed directly into the frame. 30mm 6806 bearings are pressed into cups and the cups then pressed into the frame
The traditional (61x46mm) OSBB will always use a plastic insert to fit the bearings in the frame. This setup caused a lot of creaking issues. Specialized started to supply aluminum bottom bracket cups which are permanently bonded in the frame by the dealers.