Get Your Own Bottom Bracket Tools & Maintenance Accessories for Your Bicycle

THE BEGINNER’S GUIDE TO BOTTOM BRACKET STANDARDS

The bottom bracket is an important part of your bike. If you are just getting started, you might be a bit confused about what they are. There seems to be as many standards as there are bikes, with each of them claiming to be the best. To make things more complicated, you can’t interchange them between most brands.

If you are trying to get a handle on the multiple standards for bottom brackets, then this guide is for you.

The following are the popular types of bottom brackets:

Conventional Threaded

BB90/BB95

BB30

PF30

These are not the only ones available. There are others, but these are the ones you are likely to come across as a beginner.

Conventional Threaded

This type has internal threading. There is a spindle that goes through the shell and is held in position by threaded bearing cups or threaded adaptors. The external diameter for adaptors is usually 35 mm while the internal diameter for frame shells is usually 34 mm. The width for the shell can range from 68 mm to 100 mm and maybe wider.

Shimano made it popular when it introduced versions like the Hollowtech II and XTR m960 in 2003.

BB90/BB95

This bottom bracket was introduced by Trek Bicycles and is used on some top-end mountain and road bikes. It is quite similar to what you get with integrated headsets. The cartridge bearing here is not fixed on the adaptors. What happens is that it has a frame molded specifically to take in the cartridge bearing like a slip fit. It also uses two piece cranks in combination with spindles of 24 mm diameter. You can use most bottom bracket removal tools to work on it.

BB30

This tool was specifically made so that bikes can use the crankset with a bigger spindle diameter of about 30 mm. To do this, the casings and bearings had to be bigger. It doesn’t have internal threads and it has a 43 mm inside diameter. While the standard casing width for road bikes is 68mm, mountain bikes have a 72 mm shell width. This bottom bracket has a cartridge pressing directly on the frame and it stops at snap rings that are designed in the shell frame.

Over the course of time, they are likely to wear out. So, when changing them, use bottom bracket removal tools made specifically for them. If you don’t know what to do next at any point, you should seek professional advice.

PF30

This is a standard that came after the BB30 standard. The inside diameter of its casing is about 46mm. For road bikes, the width of the frame shell is 68mm while for mountain bikes, it is 73mm. The bearings for the cartridge are fixated on aluminium or plastic adaptors. These are then pressed on the frame shell and an outer lip located on the adaptor acts as a stop for the shell face.

Just like the BB30, the PF30 was made for 30mm diameter cranks. This means that you can use cranksets for BB30s for PF30s. Also, like the BB30, the adaptors of the PF30 allow the spindle cranks to fit the PF30 standard frames.