Bicycle as a delight! And bicycles models are getting better and better. Designers have made great advancements in the technology used in manufacturing of bicyclesLighter materials are being used to construct frames, wheels, and pedals, while more efficient systems are being implemented for braking, shifting, and cranking. What I want to talk about today is the latter: cranking. The key component of actually pedaling a bicycle is the bottom bracket. The more efficient it is the better your ride; and the longer lasting the part will be.

What is a bottom bracket?

A bottom bracket is the component of a bicycle that attaches the frame to the crank arms. It allows the crank assembly to rotate as if on an axle while you pedal. See the picture to the right. 

You’ll usually know when your bottom bracket component is wearing out because it begins to feel loose and will often make a noise. If the bearings in your bottom bracket wear out be aware that most have been designed to be serviced by replacement rather than by repair.

For a long time bottom brackets had square taper ends for cranks to slide on. The square taper is the shape of the spindle that holds the cranks. The holes in the cranks aligned with the square taper in such a way that when the crank screws are tightened they stay secure.

Then around 2006 the industry developed a standard which was known as ISIS bottom brackets and Shimano countered with their proprietary octalink bottom bracket. Both of these models had splined spindles. A splined spindle has equidistant ridges that the crank slides over, and which gives more surface area contact, thus greater hold. Square taper bottom brackets worked fine; however, the surface area contact between the crank and bottom bracket was increased with both ISIS and octalink by such a large degree that the splined spindle showed obvious improvements.

Both minimizing power loss at the point of contact, hence they became best sellers instantly. The photo to the left is an ISIS splined bottom bracket. 

Recently there has been another revolution with the bottom bracket and crank interface with the introduction of many new proprietary systems in the market: BB30, PressFit 30, Shimano Press Fit just to name a few. The idea is that the bracket does not need to thread into the frame. Instead, it is pressed into the frame like a sleeve and capped. The crank is attached to the shaft via a splined surface and is then inserted through the sleeve and attached to the crank on the other side. Again the power loss is minimized; hence, these are the newest hot bike products on the market.

These hot bottom brackets are not for everyone. If you are just tooling around town, I recommend that you keep your current setup. However, if you are looking to race or keep up with the Jones's look at upgrading your bottom bracket / crank assembly with one of these new devices.If you are just tooling around town keep your current setup. However if you are looking to race or keep up with the Jones's look at upgrading your BB/crank