Shimano Square BB-UN300 Bottom bracket 68 x 123mm -Live4Bikes

Shimano Square BB-UN300 Bottom bracket 68 x 123mm -Live4Bikes

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 Shimano Square BB-UN300 Bottom Bracket 68 x 123mm: An Essential Component for Cycling Enthusiasts


Cycling has long been celebrated as a fantastic way to stay active and explore the world around us. Whether you're a seasoned cyclist or a casual rider, the importance of having reliable and high-quality components cannot be overstated. One such crucial component is the bottom bracket, which plays a significant role in the smooth functioning of a bicycle. Among the reputable options available, the Shimano Square BB-UN300 Bottom Bracket, specifically in the 68 x 123mm size, stands out as a reliable choice for enhancing your cycling experience. In this article, we delve into the key features of this bottom bracket and why you should consider purchasing it from Live4Bikes, a trusted online retailer.

Understanding the Shimano Square BB-UN300 Bottom Bracket

The bottom bracket is an essential part of a bicycle's drivetrain, responsible for connecting the crankset to the bicycle frame. The Shimano Square BB-UN300 is a square-tapered bottom bracket, which is a time-tested design known for its durability and efficiency. The 68 x 123mm specification refers to the shell width and axle length, making it compatible with a wide range of road and mountain bikes.

Key Features of Shimano Square BB-UN300 Bottom Bracket

  1. Durability: Shimano is renowned for producing robust and long-lasting bicycle components, and the BB-UN300 is no exception. It is constructed from high-quality materials, ensuring it can withstand the rigors of various terrains and riding styles.

  2. Smooth Performance: The Shimano BB-UN300 is engineered to deliver smooth and efficient power transfer. With low friction and minimal resistance, it allows cyclists to pedal with ease, optimizing energy efficiency and overall performance.

  3. Sealed Design: The bottom bracket comes with sealed cartridge bearings, which protect the internals from dust, dirt, and moisture. This design choice not only extends the life of the bottom bracket but also reduces maintenance requirements.

  4. Easy Installation: Installing the Shimano BB-UN300 is a straightforward process, making it suitable for both professional mechanics and DIY enthusiasts. The square-tapered design is a standard interface, allowing it to be used with various cranksets.

  5. Universal Compatibility: The 68 x 123mm size ensures broad compatibility with a variety of road and mountain bike frames, eliminating the worry of compatibility issues when upgrading or replacing components.

Why Purchase from Live4Bikes?

While the Shimano Square BB-UN300 Bottom Bracket is available from several retailers, choosing Live4Bikes offers several distinct advantages:

  1. Reliable Source: Live4Bikes is a reputable and well-established online retailer specializing in cycling components. They have built a strong reputation for offering genuine products and excellent customer service.

  2. Competitive Pricing: Live4Bikes consistently provides competitive pricing, ensuring you get the best value for your money. Additionally, they may offer discounts or bundle deals, allowing you to save even more.

  3. Knowledgeable Support: The staff at Live4Bikes are cycling enthusiasts themselves, which means they understand the products they sell. They can provide expert advice and assistance, helping you make an informed decision.

  4. Fast and Secure Shipping: Live4Bikes prioritizes prompt and secure shipping, ensuring that you receive your order in excellent condition and without unnecessary delays.

  5. Customer Reviews: By purchasing from Live4Bikes, you can benefit from reading customer reviews and experiences with the Shimano BB-UN300. This feedback can further reassure you about the product's quality and performance.


In conclusion, the Shimano Square BB-UN300 Bottom Bracket in the 68 x 123mm size is a reliable and durable option for cyclists looking to enhance their riding experience. Its smooth performance, universal compatibility, and ease of installation make it an attractive choice for various bike types and riding styles. When purchasing this essential cycling component, Live4Bikes stands out as a trusted online retailer, providing competitive pricing, knowledgeable support, and a streamlined purchasing process. So, gear up and get ready to elevate your cycling adventures with the Shimano Square BB-UN300 from Live4Bikes.


 How to Find the Correct Size Bottom Bracket for Your Bike

The bottom bracket is a critical component of your bicycle's drivetrain system, connecting the crankset to the frame. Selecting the correct size bottom bracket is essential for maintaining smooth pedaling and maximizing power transfer. In this article, we will guide you through the process of finding the right bottom bracket size for your bike and discuss the various types of bottom brackets commonly used in bicycles.

Understanding Bottom Brackets:
Before diving into the sizing process, let's briefly explore the different types of bottom brackets available. The choice of bottom bracket depends on your bicycle's frame design, crankset compatibility, and personal preferences. Here are a few common types:

1. Threaded Bottom Brackets:
Threaded bottom brackets are the traditional style, consisting of cups that screw into the frame's bottom bracket shell. They are commonly available in two versions: English/BSA (British Standard) and Italian. Threaded bottom brackets require a compatible frame and crankset.

2. Press-Fit Bottom Brackets:
Press-fit bottom brackets have become popular in recent years, particularly in modern carbon frames. Instead of threading, they rely on a tight press fit into the frame's bottom bracket shell. Common press-fit standards include BB86, BB90/92, PF30, and BB30. It's crucial to ensure compatibility between your frame and crankset when choosing a press-fit bottom bracket.

3. External Bottom Brackets:
External bottom brackets, often referred to as outboard bearings, are designed to be used with external bearing cranksets. They consist of two sets of bearings housed in cups that are threaded into the frame. External bottom brackets are available in different standards, such as Shimano Hollowtech II and SRAM GXP.

Finding the Correct Bottom Bracket Size:
To determine the correct bottom bracket size for your bike, follow these steps:

Step 1: Identify the Frame's Bottom Bracket Shell Type:
Check the specifications of your bicycle's frame to determine its bottom bracket shell type. Common types include threaded (English or Italian) or press-fit (BB86, BB90/92, PF30, BB30, etc.). This information is often provided by the manufacturer or can be measured directly.

Step 2: Determine the Axle Diameter:
The axle diameter is another crucial factor in selecting the right bottom bracket. It corresponds to the diameter of the crank spindle that passes through the bottom bracket bearings. Different cranksets have varying axle diameters, such as 24mm, 30mm, or 30/24mm (commonly known as DUB).

Step 3: Consider Compatibility:
Ensure that the bottom bracket you choose is compatible with your frame and crankset. Manufacturers often provide compatibility charts or guidelines to help you make the right selection. If you're uncertain, consult a professional bike shop for assistance.

Step 4: Seek Professional Advice:
If you are unsure about any aspect of selecting a bottom bracket, it's always a good idea to consult a bike shop or a knowledgeable mechanic. They can offer valuable expertise and help you make an informed decision based on your specific bike model and requirements.

Selecting the correct size bottom bracket for your bike is vital for maintaining optimal performance and compatibility between your frame and crankset. Understanding the various bottom bracket types, identifying your frame's specifications, determining the axle diameter, and considering compatibility are essential steps in the selection process. When in doubt, seek guidance from professionals who can provide personalized advice and ensure a smooth and reliable cycling experience. Remember, a well-chosen bottom bracket will contribute to a more enjoyable and efficient ride.

  Types of BB

 There are several types of bottom brackets (not "bottom brakes") used in bicycles. The bottom bracket is the component that connects the bicycle's crankset to the frame and allows it to rotate smoothly. Different types of bottom brackets have been developed over the years, each with its own design and compatibility with specific cranksets and frames.

Here are some common types of bottom brackets:

1. Threaded (BSC/English): This is the traditional type of bottom bracket, where the cups are threaded into the bicycle frame.

2. Press-fit: Press-fit bottom brackets do not have threads and are instead pressed directly into the frame. They are generally found in modern carbon frames and are known by various names like BB86, BB90, BB92, BB30, PF30, etc.

3. Square Taper: Square taper bottom brackets have a square-shaped spindle that fits into square holes in the crankarms. They were popular in the past but are less common in modern bicycles.

4. Octalink: Shimano's Octalink bottom brackets feature eight splines on the crankarm interface, providing a larger contact area for improved power transfer.

5. ISIS Drive: The ISIS Drive system also uses splines but with a 10-spline pattern on the crankarm interface.

6. Hollowtech II: This is a type of bottom bracket system developed by Shimano, where the bearings are housed in outboard cups.

7. BB30/PF30: These bottom brackets have larger-diameter spindles and use press-fit cups. BB30 spindles are 30mm in diameter, while PF30 spindles are 30mm but have a wider shell.

8. BB386EVO: A variant of BB30, BB386EVO bottom brackets have a wider bottom bracket shell and a 30mm spindle.

9. BBright: Developed by Cervelo, this bottom bracket system combines elements of BB30 and PF30.

It's important to note that the bicycle industry is constantly evolving, and new standards and bottom bracket types may have emerged since my last update. Additionally, different bike manufacturers may have their own proprietary bottom bracket systems. Always check the specifications of your specific bicycle model to know which type of bottom bracket it uses and to ensure compatibility with replacement parts or upgrades.