What makes bikes unique is the fact they come in all shapes and sizes. Not only the bike itself but all the components that bring it together. The stem is a part of the bike that you really benefit from being the correct size.
Bike stems come in all different sizes, and they are very simple to change over when required. Although one very common problem a lot of cyclists find with stems is they don’t often tell you what size they are on them.
To find out, you generally must measure them yourself. In this article, we are going to tell you everything you need to know about stems and how to measure them. We will be discussing the following:
- What Is A Bike Stem?
- Why Is It Important To Have The Correct Size Stem?
- How To Measure A Bike Stem
What Is A Bike Stem?
The bike stem is what connects the forks and the handlebars together. A modern stem is quite simply referred to as a stem. A classic stem is referred to as a quill stem.
Modern stems attach to the forks, and classic stems attach inside the forks. Some stems can even be part of the handlebars, which we call integrated.
Stems come in all different sizes, and also you get different angles. This is because they are vital to getting the perfect fit on your bike.
A stem can turn your bike into an aggressive race machine or make it a more upright, comfortable touring bike ride.
Why Is It Important To Have The Correct Size Stem?
Many cyclists underestimate the difference a stem can make when it comes to riding your bike. Here’s why it’s important to have the correct size stem.
If you have a stem that is too long, it will stretch you far out front putting you in a very aggressive position. If you have a stem that is too short, it can tighten you up too much and make you too upright. The right size stem will put you in a comfortable position.
The stem size makes a big difference in how a bike handles. A short stem will make the steering feel very responsive and agile, while a longer stem will offer more stability and a very predictable feel to it.
A longer stem will lean you over the front more compared to a shorter stem keeping you backward. The stem greatly influences where the rider sits on the bike and how the weight sits on the bike.
How To Measure A Bike Stem
Now for the fun bit, let’s teach you how to measure a bike stem. Here’s our go to proven method when it comes to measuring a stem. Here’s what you’re going to need:
- Vernier Caliper
- Measuring Tape
- Pen And Paper
- Protractor (Optional)
Either will be fine, but we recommend the vernier caliper over the measuring tape as it’s just much more accurate and easier to use compared to the measuring tape. When it comes to the stem, there are three main measurements you’re going to want. The length of the stem, the handlebar grip, and the angle.
Step One: Preparation
The first thing you need to do is find a safe place to start measuring and have everything you need with you. You do not need to remove the stem as many people would advise, you can easily do it with the stem on or off the bike.
Step Two: Measure The Length
The first place we need to measure is the length. This is how long the stem is from where it sits on the fork to where it holds the handlebars. A very common misconception is that it’s measured from end to end when it isn’t.
The measurement has to be made from the center of the fork steerer, where the center of the top cap sits, to the center of where the handlebars attach. We will get this in a picture below, so you know exactly where to look.
So measure from one end to the other and then make a note of the length. This will be the stem length itself and the most important measurement you will need. It will typically be in an increment of 10mm, such as 80mm, 90mm, or even 120mm.
Step Three: Measure The Handlebar Grip
Next, you are going to need to measure the diameter where the handlebars are held. This will be a simple measurement of the hole where the handlebars sit or the measure the handlebars themselves.
It’s important to remember that we are not measuring the diameter just from one side to the other. Once done, make a note of this.
Although modern stems are normally 31.8mm, but some are smaller, and it’s important to measure this as it can be really easy to end up changing a stem and it being wrong when you come to attach the handlebars.
Step Four: Measure The Angle (Optional)
If you want to know everything about your stem, then you can also measure the angle. Generally, a modern standard stem will be around 6 degrees, and you can either have it give you an upright comfort position or flip in and have it give you an aero racing position. It’s worth mentioning there are lots of different angles available for customization.
You must first have the bike on a level surface to measure this angle. It’s easier if you have the stem separate from the bike, but you can get a good gauge even with it on the bike.
Then you need to take the protractor, put it level and then read the angle from the protractor. Once done, make a note.
A Final Thought
Well done! You now know how to measure a bike stem.
It’s a handy skill to know, and changing the stem is a great way of fine-tuning the bike to suit you perfectly. We highly recommend experimenting with different stems as it can give you a much better cycling experience having the right one for you.
Thanks for taking the time to read our article.
Robbie Ferri has spent years working in a bike shop, has worked with industry leading brands on product creation, has been a semi pro athlete, and is a fully qualified strength and conditioning coach. He has broken World Records, bikepacked all over the World and raced ultra distance at a top-level.