Bottom Brackets for Bicycles – The Pivotal Component
The bottom bracket is an almost invisible yet crucial component on a bicycle and forms the link between the frame and the crankset. As part of the drivetrain, it enables smooth power transfer from the pedals to the chain and thus to the rear wheel. We have high-quality bottom brackets for all common standards and bicycle types in our range.
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What is a Bottom Bracket and What is it Used For?
The bottom bracket is a bearing system that is installed in the bottom bracket shell of the bicycle frame. It consists of ball bearings or sealed bearings that are mounted in a sleeve or directly in the frame. The main functions of the bottom bracket are:
- Power Transfer: Enables efficient transfer of pedaling force to the crankset
- Friction Reduction: Ensures smooth and consistent pedaling motion
- Stability: Guarantees a stable connection between crankset and frame
- Protection: Protects the moving parts from dirt, moisture, and wear
A defective or worn bottom bracket manifests through creaking, grinding, or difficult pedaling and should be replaced promptly.
Bottom Bracket Standards: Overview of the Most Important Systems
The variety of bottom bracket standards results from the continuous development of bicycle technology. Here are the most important standards:
BSA/British Standard Thread (BSA 68/70)
The BSA standard (British Standard) is one of the oldest and most widespread standards. The bottom bracket is screwed into a thread with 1.37" x 24 TPI. The shell width is 68mm or 70mm. This standard is commonly found on road bikes, mountain bikes, and trekking bikes.
ITA/Italian Thread (ITA 70)
The Italian thread has a diameter of 36mm x 24 TPI and a shell width of 70mm. Special feature: Both sides have right-hand threads, which must be considered during removal. This standard is mainly used by Italian road bike brands.
BB30 and BB30A
BB30 is a press-fit system with a 68mm wide shell and 42mm internal bore. The bearings are pressed directly into the frame. BB30A is a further development with asymmetric bearing cups. This standard offers a stiffer connection and is often used on high-end road bikes.
PF30 (PressFit 30)
PF30 combines the 42mm bore of BB30 with plastic bearing cups that are pressed into the frame. The system is more maintenance-friendly than BB30 and is found on many modern road bikes and mountain bikes.
BB86 and BB92 (PressFit)
These Shimano standards use a 41mm bore with pressed plastic bearing cups. BB86 has a shell width of 86.5mm, BB92 of 91.5mm. They are compatible with Shimano Hollowtech II cranks and are widely used on MTBs and road bikes.
BB Shell Standards for E-Bikes
E-bikes often use special bottom bracket standards such as BB52 or STEPS-compatible systems that can withstand the higher loads from the electric motor.
Materials and Quality Features
High-quality bottom brackets are characterized by the following properties:
- Precision Bearings: Sealed bearings with low tolerances for optimal smoothness
- Seals: Effective protection against dirt and moisture
- Material Quality: Stainless steel for long service life
- Surface Treatment: Anodized or coated surfaces for additional corrosion protection
Installation and Maintenance
Installing a bottom bracket requires special tools and expertise. Important points:
- Thread Inspection: The threads in the frame should be checked before installation
- Assembly Grease: Using appropriate assembly grease prevents corrosion
- Torque Specification: Adhering to manufacturer specifications is essential
- Regular Maintenance: Checking for play and smooth operation extends service life
The Right Choice for Your Bicycle
When selecting the appropriate bottom bracket, the following factors should be considered:
- Frame Compatibility: The standard must match the bottom bracket shell exactly
- Crank Compatibility: The bottom bracket must match the crankset being used
- Application Area: Road, terrain, or e-bike require different specifications
- Budget: From affordable standard bearings to premium ceramic bearings
A high-quality bottom bracket is an investment in the longevity and performance of your bicycle or your next dream build. Browse our range and find the perfect bottom bracket for your bicycle – for optimal power transfer and years of riding enjoyment.