The bottom bracket is the unsung hero of your bicycle, quietly performing the critical task of allowing the crankset to spin smoothly while you pedal. It’s a small but mighty component that connects your bike’s frame to the drivetrain, ensuring efficient power transfer. However, the world of bottom brackets can be perplexing, with various standards and technologies tailored to different bikes and brands.

In this blog, we’ll demystify the topic, exploring the different types of bottom brackets, how to choose the right one for your bike, and which types are commonly associated with major bicycle brands.

The bottom bracket is housed within the bottom bracket shell of the bike frame. It consists of bearings and a spindle that connects to the crank arms, allowing the crankset to rotate. Choosing the correct bottom bracket involves understanding compatibility with your bike frame and crankset.

Types of Bottom Brackets

1. Threaded Bottom Brackets

Threaded bottom brackets screw into the frame’s bottom bracket shell, with threads machined into the shell.

Common Standards :

• BSA (British Standard Thread/English Threaded) : The most prevalent threaded standard, used on a wide range of bikes.

• Italian Threaded : Found on Italian bikes like Pinarello and Colnago, featuring right-hand threading on both sides.

Advantages :

• Reliable and creak-resistant.

• Easy to service and install.

Disadvantages :

• Limited to frames with threaded shells.

Brand Compatibility :

• BSA is used by brands like Trek, Specialized, and Cannondale on many road, mountain, and gravel bikes.
• Italian threading is often exclusive to traditional Italian manufacturers.

2. Press-Fit Bottom Brackets

Press-fit bottom brackets rely on a friction fit, where the bearings or bearing cups are pressed directly into the bottom bracket shell.

Common Standards :

• BB30 : Bearings are pressed directly into the frame without cups. Known for large-diameter spindles and low weight.

• PF30 (Press-Fit 30) : A variation of BB30 that uses bearing cups.

• BB86/BB92 : Bearings are housed in plastic cups, pressed into the frame.

• BBRight : Proprietary to Cervélo, with asymmetric spacing for improved power transfer.

Advantages :

• Allows for wider frame designs and larger spindles, increasing stiffness.

• Lightweight.

Disadvantages :

• Prone to creaking if not installed correctly.

• Can be challenging to remove or service.

Brand Compatibility :

• BB30 and PF30 are commonly used by Cannondale and Specialized.

• BB86/BB92 is a favorite among Shimano-equipped bikes like Trek, Giant, and Scott.

• BBRight is exclusive to Cervélo.

3. External Bottom Brackets

External bottom brackets place the bearings outside the frame. These are often paired with Shimano Hollowtech II and SRAM GXP cranksets.

Advantages :

• Lightweight and durable.

• Improved stiffness due to wider bearing placement.

Disadvantages :

• Requires precise installation to avoid creaking.

Brand Compatibility :

• Widely used by brands using Shimano (e.g., Trek, Specialized) or SRAM drivetrains.

4. Integrated Bottom Brackets

Integrated systems streamline the bottom bracket design, with bearings often located directly on the crank spindle.

Examples :

• Campagnolo Ultra-Torque : Bearings are semi-integrated into the crank arms.

• Shimano Press-Fit : Combines press-fit with the simplicity of Shimano’s design.

Advantages :

• Lightweight and aesthetically sleek.

• Fewer parts, reducing potential creaking.

Disadvantages :

• Limited cross-compatibility.

• Proprietary systems can make replacements challenging.

Brand Compatibility :

• Campagnolo Ultra-Torque is common on high-end road bikes from Italian brands like Pinarello and Colnago.

• Shimano Press-Fit is frequently seen on bikes from Giant, Canyon, and Bianchi.

5. T47 Bottom Brackets

T47 is a modern standard that combines the reliability of threaded systems with the benefits of wider, press-fit shell dimensions.

Advantages :

• Creak-free operation.

• Compatible with a wide range of cranksets and frame designs.

Disadvantages :

• Requires a frame with T47 threading, which is less common.

Brand Compatibility :

• Increasingly adopted by high-end and custom bike manufacturers like Trek and Moots.

Selecting the correct bottom bracket requires understanding your bike’s frame, crankset, and riding needs.

1. Identify Your Frame’s Bottom Bracket Shell

Every bike frame has specific dimensions and standards for the bottom bracket shell. Here’s what to check:

• Shell Width : Typically ranges from 68mm (road) to 92mm (mountain).

• Shell Diameter : Key to determining press-fit or threaded compatibility.

2. Determine Your Crankset Standard

The crankset spindle diameter and type (e.g., 24mm for Shimano Hollowtech II, 30mm for BB30) must match the bottom bracket.

3. Match Riding Needs

• Road Cyclists : Prioritize stiffness and low weight for efficient power transfer. Standards like BB86 or threaded BSA are common.

• Gravel Riders : Look for durability and resistance to contamination. Threaded or T47 options are popular.

• Mountain Bikers : Emphasize durability and ease of maintenance. BB92 and threaded options excel here.

4. Consider Maintenance

Threaded bottom brackets are easier to install and service, making them ideal for riders who perform their own bike maintenance. Press-fit options, while lighter, may require professional installation.

5. Factor in Upgrades

Consider ceramic bottom brackets for less friction and a longer service life.

Here’s a quick guide to the bottom bracket types commonly used by popular bike brands:

• Trek : Often uses BSA on road bikes, BB92 on mountain bikes, and T47 on high-end models.

• Specialized : Frequently uses PF30 or BB30, particularly on performance-oriented models.

• Cannondale : Known for BB30 and PF30 standards, reflecting their focus on stiffness and weight savings.

• Giant : Typically uses BB86 for road bikes and BB92 for mountain bikes, reflecting Shimano compatibility.

• Cervélo : BBRight is the proprietary standard for most of their bikes, emphasizing stiffness.

• Colnago : Italian-threaded on traditional frames and Press-Fit on modern carbon designs.

• Scott : Predominantly BB86/BB92, aligning with Shimano’s drivetrain systems.

• Pinarello : Uses Italian threading on older models, with BB86/BB92 on newer bikes.

• Moots : Adopts T47 for its durability and reliability.

1. Consult Your Bike’s Manufacturer : Most brands provide bottom bracket specifications in their manuals or online.

2. Invest in Quality : High-quality bottom brackets last longer and reduce creaking. Brands like Chris King, SRAM, and Shimano are reliable choices.

3. Seek Professional Installation : Especially for press-fit systems, professional tools and expertise can prevent creaking and premature wear.