For many bikers, hardly any part of the bicycle is as inconspicuous and mysterious as the bicycle bottom bracket. Yet the bottom bracket, as the inner bearing is often called, has to withstand incredible loads. In addition to the drive forces acting on the bicycle bottom bracket, there are also the loads exerted by the rider himself. The times in which defective and broken axles were the order of the day, are fortunately over.
Through the permanent development of the bicycle bottom bracket, you can now choose from a variety of different designs. The modern standards include, among others, multi-tooth bottom bracket bearings such as the Octalink and BB, BSA square bottom bracket bearings as well as the Hollowtech II ISIS bearing.
Different standards for different applications
Unfortunately, the different standards that have developed over the years, are not compatible with each other. When replacing individual parts, such as the crank, you must orient yourself to the existing bottom bracket. Often, the exchange of the complete bearing with the cranks is cheaper than the purchase of individual parts.
When buying a bicycle bottom bracket are some things to keep in mind. So you must definitely pay attention to the housing widths, which vary from bike to bike. In addition, the thread type and the question of whether it is pressed or screwed bearing shells play a major role. The data sheet of your bike gives you information about which standard or which bottom bracket can be installed on your bike.
Square bottom bracket
The square bottom bracket is particularly often installed on older bikes. Until about 2000, the bottom bracket with intrigierte square axle was standard, with road bikes mountain bikes and all other wheels.
Same as with the square bottom bracket, the axle is integrated into the bottom bracket with the multi-tooth bearing. The crank is put here on the left and right on the axle. The reception for the crank is designed as a multi-tooth, hence the name of this bottom bracket standard.
Hollow axle bottom bracket
In contrast to the multi-tooth or square bottom bracket, this type of bottom bracket has no axle firmly integrated. This standard is seen today in most mountain bikes, cross bikes or city bikes. The axle of the crank is guided through the hollow space of the bottom bracket. Here you have to consider which installation width and housing size is required. In addition, you must note which installation size of your crank has.