Once upon a time, all bikes were made of steel. And the bottom bracket axle was a solid steel rod. There were cups in the bearings into which loose ball bearings fitted, with the axles having a curved surface which pushed against the ball bearings.
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.
The evolution of road bikes may have provided cyclists with frames that are lighter, stiffer and more aerodynamic, but there has also been a substantial increase in the number of bottom bracket and crank axle designs. The once ubiquitous threaded bottom bracket shell has given way to larger threadless designs while the diameter of crank axles has also grown. Both may have helped elevate the performance of contemporary road bikes but consumers have been left to contend with myriad options and some frustrating incompatibilities.
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.
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.
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 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.