How To Measure The Bottom Bracket – Bike Tips and Tricks

Is it time to get the bike's crank updated or the bottom bracket? This guide is here to make sure that you measure the bottom bracket perfectly, we know many people have been having trouble with that.
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Taking care of your bikes is equally important as riding them, only if they have the perfect shape will they be able to perform as they originally should. Speaking from experience, I have learned that keeping your bike in better shape is very important for good performance.  We know that bikes are complex and simple machines at the same time, and from time to time we have to update and replace some parts-such as the Bottom Brackets.

Updating the bike components from time to time enhances their performance even the crank arms. May it be cranks or bottom brackets, every part uniquely extends the capabilities of bikes. If you are thinking about updating the bottom bracket then it is vital that you know the correct bottom bracket to go for!

Bottom Bracket- An Introduction

Cartridge Type Bottom Bracket

For people that are getting confused about bottom brackets, this is for them. A bottom bracket is found at the intersection of the down tubes and the seat on a bike frame. 

The bottom Brackets have two bearings, and you need to know about them if there is a need for replacement. The first one can be on any side, just make sure that the pedal hinge is suited. Some other things to look out for here are the chainrings and pedals, they need to turn freely so make sure that the bearings are placed properly.

The assembly for the bottom bracket is going to be a tad different, some might need spacers and lock rings but that depends on the design of the bottom brackets.

How To Measure The Bottom Bracket

Going to the market in search of the bottom brackets can be very bewildering, especially if you don’t know the correct bottom bracket size. That is why this guide is here to help you out, it may seem difficult to measure but there are no technicalities involved.


Measuring a bottom bracket might be easy but it is impossible without the right tools. Here are the tools needed to correctly measure:

Calipers Or Metric Rulers

To measure the internal and external dimensions you will be needing this tool. Think of it as a bike compass!

Bottom Bracket Spindle

This is an axle where the pedal rotates, you will need it to screw to the crank arms.

This collection of Bottom Bracket Tool(s) will make you fully prepared for the measurement process.

Measure Bottom Bracke

Start With A Good Preparation 

To get things started, you will need to be fully prepared, both mentally and by having the right tools by your side. The one component of the bottom bracket that needs to be changed now and then is the spindle, there is no repairing that, so keep that in mind.

The spindle also needs to be measured if you want to replace the bottom bracket. We already mentioned that you will either need a metric ruler or a set of calipers as the bottom bracket is measured in mm.

Measure The Bottom Bracket’s Shell

The Bottom Bracket Shell is where you have to start, flip the bike upside down, and then hold either the calipers or the metric ruler against the casing. From here you have to measure the length of one end to the other end. Not to mention the length of the spindle which is located inside the shell. When you have all the required measurements, it will be time to move to the next step.

In the case of confusion, the majority of the bottom bracket’s shells measure between 68-73 millimeters long.

Measure The Bottom Bracket’s Spindle 

In the last step, all we have to do is measure the bottom bracket’s spindle. For this, we have to remove the crank arms first. When the crank arms are removed then measure the length of the bottom bracket’s spindle from one end to the other, it will be in millimeters.

On some bikes, the cranks are attached via a series of nuts rather than bolts. In this case, measure the length of the spindle but don’t include the parts connected with the spindle.

There you have it, you have successfully measured the bottom bracket!

Why You Should Get A New Bottom Bracket?

Premium-Quality Bottom Brackets make sure that you enjoy years of amazing rides without any kind of problems but keeping them maintained is the tricky part. We have discussed the bottom bracket shell and bearings, they go out of shape often.

Bottom Brackets Bicycle Carriage

Either the bearings could become ruptured or the whole bottom bracket can become unfastened, you need to be prepared for that. When that happens, either you will get to experience excessive movement or some annoying noises, those are so much that you won’t be able to ride in peace.

I remember, in my early days of bike riding, I decided to take the long route home to enjoy my time on the bike a little bit more. Just halfway into the journey, I started hearing weird creaking noises which I figured were coming from the bottom bracket of my bike. It was so frustrating to ride but the incident did spark my interest in bike components. Since that day, I dedicate every third Sunday of the month to bike maintenance. 

That is why it is always recommended that you replace the bottom brackets whenever this problem occurs. Ensuring that the bottom bracket is in good condition will result in years of hassle-free riding.

The Different Types Of Bottom Brackets

Getting a bottom bracket is really difficult, we get that, there are different shapes and sizes but there are also different types of Bottom Brackets. Let us discuss them in detail, here are the types:

  • Press-Fit Bottom Brackets
  • External Bottom Brackets
  • Cartridge Type Bottom Brackets

Press-Fit Bottom Brackets

Let’s start with the Press-Fit Bottom Bracket first. All the mid-end to high-end road bikes and mountain bikes, even with the carbon frames have Press-Fit Bottom Brackets. These types of brackets work well because their bearings are pressed right into the frame of the bike, may it be in aluminum or race cups, these cups are then molded into the bike’s frame.

The main reason why these types really work so well is that they use broader bottom bracket shells, which don’t affect the axle width. When this happens, users can install large down tubes, this does not affect the bike frame in any way, opening a lot of customization options.

Having the Press-Fit Bottom Brackets enhance the power transfer between the rider and the bike frame, as it decreases the bottom bracket flex. If that is your main goal then you should definitely go for this type.

Using A Bottom Bracket Wrench

External Bottom Brackets

Next up we have the external bottom brackets. These types of bottom brackets are where the cartridge bearings lie in the aluminum cups at the exterior of the bottom bracket shells. These types of brackets increase the flow of transfer but you need a bigger diameter axle for that which will enhance the bracket’s rigidity.

Having this type installed on your bike will increase the overall toughness of the ride but there could be a lot of disadvantages too. Anything can go wrong here, if the bearings are not properly installed then they could die a LOT faster than expected.

It is also recommended to get ceramic bearings because of their amazing smoothness. Also, check the shell width before getting this type of bottom bracket.

Cartridge-Type Bottom Bracket

Let’s take a look at another bicycle bottom bracket type. The Cartridge-Type Bottom Brackets are old-school brackets that are fitted into different kinds of bikes. They have a small internal diameter and the axle bearings are sealed into a metal cylinder. 

These types of bottom brackets cannot be replaced, once they go out, you just merely replace them. But, I would suggest getting a bottom bracket that aligns with your riding style. For example, if you are looking for better power transfer with less flex, you should opt for Press-Fit bottom brackets. I use press-fit bottom brackets on my bike and they are amazing in terms of transferring the power between my bike and me. 

Which Type Of Bottom Bracket Should You Go For?

People look for bottom brackets but most of the time they don’t even know what they want, or what would be best for them. Even if you ask people some bike terms like spindle length, spindle component, or even spindle diameter, they will have no idea what you are talking about.

Hence proved it is very important to know what kind of bottom bracket is going to suit you the most. These bottom brackets will also be identified by frame type and size, this is because some carbon frame models are made to fit a single type of bottom bracket only. 

From my experience, premium-quality bottom brackets have always been a better option. They last longer and have a better performance than their cheap counterparts.

We already talked about the different types of bottom brackets, it is up to you now to choose the best one for yourself. Just make sure that the bottom bracket that you choose is fully compatible with your bike. Threaded bottom brackets are also a good option to go for though!


What Is A Bottom Bracket On A Bike?

A bottom bracket is used to connect the bicycle’s crankset with the frame of a bike. This allows the crankset of the bike to rotate independently. 

Are Threaded Bottom Brackets Better?

Threaded Bottom Brackets are simple, reliable, and easy to install. They are easier to maintain and provide a secure threaded interface which makes them less vulnerable to any noise issue. They have a wide compatibility but the choice on what bottom bracket you should get should solely depend on your bike’s frame and your riding preferences.


Measuring the Bottom Bracket isn’t complicated, you just need to have the right skills and the right tools with you. The whole process can be completed in a matter of minutes. Another important thing that we discussed in this guide is the different types of bottom brackets, each of them has its dedicated advantages and disadvantages.

We hope that after going through this guide, you can take all the measurements by yourself without any kind of problems. If you have any kind of problems or queries, just reach out to us in the comments!

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