If you are here, I assume you’ve just heard the term bottom bracket from someone. But, you are not sure what exactly it is. Or you know the basics and want to know more about it. In both cases, stay and you won’t be disappointed.
This guide will take you through an explanation of what a bottom bracket is and bottom bracket types. Also, you’ll learn to identify the type of bottom bracket you have and how you can maintain it.
What is the Bottom Bracket on a Bike?
A bottom bracket is the component of a bike that connects a bike’s crankset to its frame and allows it to rotate freely. Its function is to withstand load and abuse, as a result of your ride. Moreover, it affects the transfer of power between the legs of the biker and the terrain.
What are the Components of a Bottom Bracket?
- Spindle (The crankset will attach to it)
- Bearings (helps in rotating the spindle and the crankset)
- Cups (fixed and adjustable)
- Lockrings
- Types of bearings (sealed or loose)
Types of Bottom Brackets
Do you want to know the types of bottom brackets? In this part, I will explain it in detail.
- Threaded Bottom Brackets
- BSA (British Standard Cycle) or English Threaded
- Square Taper Bottom Brackets
- Press Fit Bottom Brackets
- BB30, BB86/92, PF30
- Eccentric, BMX, SRAM DUB
Threaded Bottom Brackets
A threaded bottom bracket threads into the bike’s frame. They have threaded cups. The cups also have bearings. These bearings can be loose, sealed, or caged.
They are present in low to mid-end models and are easy to maintain and last longer. Their installation is difficult and often requires specific tools. Threaded bottom brackets are more common in cheaper bikes.
BSA (British Standard Cycle) or English Threaded
These are also threaded bottom brackets. It will have a thread on the inside of the frame. They are popular due to their ease of servicing and replacement.
Square Taper Bottom Brackets
Before square taper, cottered bottom brackets were more popular. Cottered bottom brackets use cotter pins for securing the crank to the spindle.
But, a square taper bottom bracket uses bolts instead of pins into the spindle. Besides, it comes in the form of a cartridge, having sealed bearings. With that said, there is no need to clean or re-grease it.
Press Fit Bottom Brackets
These are pressed in the bike frame. The term unthreaded is also sometimes used for it. It requires a non-threaded bottom bracket shell to fit tightly. They are lightweight and stiff.
Servicing these brackets is difficult. You have to replace the entire unit rather than replace individual parts. Expensive and high-end racing bikes have press-fit bottom brackets.
BB30, BB86/92, PF30
BB30 is another press-fit bottom bracket. So, it will have no thread on the outside. Besides, it has no removable cups between the bearings and the frame. It is named so because it can fit a 30mm spindle crank rather than the standard 24mm.
For a cyclo-cross or a road rider, the BB86 is preferable. The reason is that it offers a perfect balance between durability and weight. It has sealed bearings that are further mounted in cups and pressed into a non-threaded shell of 41mm.
PF30 is a press-fit bottom bracket, meaning it will not have a thread on its outside. Its bearing is similar to BB30. How is it different? For better durability, it has a cup between the frame and the bearings. Also, it has a bottom bracket shell’s internal diameter of 46mm. The bearings are placed in the same manner as that for BB86/92.
Eccentric, BMX, SRAM DUB
The spindle of a concentric bottom bracket revolves around the bottom bracket’s centerpoint evenly. Eccentric is the opposite of it; it rotates away from the center point of the bottom bracket.
A BMX bottom bracket is available in two forms. It can either be a one-piece setup, having loose/caged bearing, or a three-piece setup square taper solution.
The SRAM DUB (Durable Unified Bottom) has a crank spindle of 30mm, making it light and stiff. Whether you have BB30, PF30, BB886/92, or BSA, you can easily install this crank in your rig.
How to Identify Bottom Bracket on Your Bike?
Here is an overview to identify the bottom bracket of your bike:
- The first step is to remove the crank.
- If you have a press-fit bottom bracket, there will be no tool fittings on the inside or outside. They are simply pressed into a non-threaded bottom bracket shell.
- Now, a threaded bracket is also installed in a non-threaded shell. But, its left and right cups have tool fittings that thread together inside the shell.
- However, you can get confused and damage your bottom bracket. If that’s the case, consult a professional.
Signs of Bad Bottom Bracket of a Bike
Below I have mentioned the symptoms of a bad bottom bracket of a bike:
- You’ll hear the bearings making unpleasant creaking noises.
- Look for clicking or grinding noises. This will happen during pedaling. This sound hints at either a worn bottom bracket or a bottom bracket that is lubricated poorly.
- Play in your bottom bracket. You will notice it as soon as you wiggle the cranks or frame. This is also an indication of a damaged or worn bottom bracket.
- There could be a collection of debris or dirt in the area of the bottom bracket. This indicates that the seals on the bottom bracket could be damaged. As a result, water or dirt can get inside the bracket.
How to Maintain the Bottom Bracket of a Bike?
Here are some maintenance tips to ensure your bottom brackets last long:
- The most important thing to do is to keep the whole area of your bike nice and clean.
- Always make sure that you check the preload adjustment at least once or twice regularly.
- You can clean your bottom bracket by removing the crankset from your frame. Avoid using high-pressure power washing as it is not suggested.
- To ensure the correct spinning of your bearings, rotate them using your fingers.
- Now, start cleaning the old grease from all the contact surfaces. When you are done cleaning, apply some new grease.
- Corrosion on your bottom bracket bearing leads to failure more than anything else.
Correct installation of a bottom bracket is also essential to make them last long. Installing it both loose or tight can lead to premature wear and harm to the bracket.
Conclusion:
This was all about bottom brackets. I hope it will be easier for you now to identify the kind of bottom bracket you have and how to care for it. Want to ask more questions? Head over to some of the commonly asked questions of people. You’ll find their answers in the next section.
Frequently Asked Questions
1. What happens if the bottom bracket fails?
Failure of a bottom bracket means bad bearings and the entire assembly becoming loose. Therefore, it makes it difficult to pedal. Riding a bike with a failed bottom bracket can be unsafe. You’ll also notice an increase in frame flex when you pour on the power. Ultimately, you’ll need to replace it.
2. How often should I service my bottom bracket?
The bottom brackets a few years back needed to be lubricated and greased several times. However, the design of bottom brackets these days is such that you need to replace them once they wear out. Moreover, a bottom bracket can last for about 1-2 years. But, if a bike is exposed to moisture or dirt, it can wear out sooner. In addition, if the bottom bracket is not properly installed, you’ll have to replace it.
3. Can I replace the bottom bracket myself?
Like any other component of a bike, your bottom bracket also needs replacement with wear and tear. Now, coming to your question, yes, you can replace it on your own. You’ll need some tools and patience to carry out the process.