FREE U. For those who are looking to upgrade the cranks on your mountain bike, or just need a replacement bottom bracketit's very important to make sure you get the correct bottom bracket for the job. The two major dimensions that differentiate bottom brackets of similar types are the shell width and spindle diameter.
The bottom bracket shell of a bicycle is the part of the frame where the spindle of the cranks go through. The bottom bracket and spindle together form the foundation of the drivetrain on your road bike or mountain bike. All the different standard dimensions can make it hard to determine what kind of bottom bracket shell your frame has and what bottom bracket bearings you need. How can you even tell what bearings and bottom bracket shell your frame has?
Your bottom bracket is housed in the bottom bracket shell of your bike frameit connects your chainset to the frame and allows the cranks to turn smoothly. When selecting a replacement bike bottom bracket you need to make sure that you get the correct model. This guide will help you get the right one to fit your bike and also your pocket.
The bottom bracket on a bicycle connects the crankset chainset to the bicycle and allows the crankset to rotate freely. It contains a spindle that the crankset attaches to, and the bearings that allow the spindle and cranks to rotate. The chainrings and pedals attach to the cranks.
The BB assembly may also consist of spacers and lockrings, etc. A good-quality BB, correctly installed, should serve you with years of trouble-free riding, but bearings can wear out or the BB can become loose. Find out more about the differences between BB standards and to help you choose which one is right for you. Bottom bracket spares.
There are now several different crank bearing systems and standards. The different standards do not allow interchangeability between bearings or cranksets. Having some knowledge of the standard will help the mechanic be aware of service options.
By Benedict Pfender. This comprehensive guide tells you everything you need to know about bottom brackets — from a breakdown of all the bottom bracket systems available and their compatibility with one another to how a bottom bracket works and how to stop a bottom bracket creaking, this guide has it all. Below we rundown each of the major bottom bracket systems currently available, along with advantages, disadvantages, notes on compatibility, and some input from their proponents on why they exist:. Modern, external cup threaded bottom brackets are among the most common of standards.