Tips To Choose the Right Mountain Bike Handlebar Clamp Diameter

Handlebars are one of the mountain bike components that have a profound effect on riding comfort and control. The handlebar affects how a rider controls the bike and helps balance the rider's weight correctly on the bike. The handlebar provides a mounting place for the brakes, gear shifters, and any other controls the rider might want to include on the bike. The handlebar is attached to the stem with a handlebar clamp which has to be the right diameter for a mountain bike. To gain a comprehensive understanding of the anatomy of a mountain bike as a beginner, read this Book by Fury. 

When choosing a mountain bike handlebar clamp diameter, measure the bike’s stem to ensure compatibility. Consider the overall size of the clamp, as a larger clamp can result in stiffer steering. Also, take note of the clamp’s weight, as a heavy clamp can affect the rider’s balance and control. Finally, the rider’s personal style may also play a role in selecting the type and color of the clamp for their bike. 

A mountain bike handlebar clamp is a device like this used to attach the handlebars to the stem of a mountain bike. It typically consists of two clamping bolts that can be tightened to secure the handlebars in place. This allows the rider to adjust the position of the handlebars to their desired height and angle. This article will look at what factors to consider when choosing a handlebar clamp for a mountain bike. 

Having a handlebar with the right diameter can greatly affect how much comfort and control you have during a ride. This guide aims to give you a deeper understanding of mountain bike clamp sizes and provides a step-by-step guide that shows you how to measure the handlebar of your MTB.

The mountain bike handlebar clamp diameter is important for ensuring a great ride, as the handlebar must be securely attached to the mountain bike using the correct size clamp.
All the handlebar specs are typically included on the product listing or in the manufacturer's instruction manual. Image Source: Amazon.

You may also be interested in learning the difference between flat and riser handlebars and how to choose the right one. If so, be sure to read our related article. Also, if you've ever wondered if mountain biking is good for beginners, then you'll definitely want to check out that article too.

How To Measure the Diameter of a Mountain Bike Handlebar

When you visit cycling forums, you will see many cyclists ask how to measure the diameter of mountain bike handlebars. While the process may appear difficult, it is actually not that complicated. 

To measure the diameter of a mountain bike handlebar, measure both the clamp area and the grip area. The clamp area is located at the center of the bar where the stem attaches to the handlebar, while the grip area is at the end of the handlebar where the rider places their hands.

Our article about how to choose a handlebar grip diameter explains how to measure the outer edges of a handlebar when replacing worn-out grips with grips like these. And our guide on how to remove mountain bike grips will help you to remove and replace grips if necessary.

There are two non-technical methods that can be used to measure the diameter of mountain bike handlebars, the caliper method which is shown in this video tutorial by @RomansDowntime, and the string or paper circumference method. It is advisable to have a caliper like this in your toolkit so that you can easily and accurately measure any tubes on your bike.  

Our ultimate list of tools needed for mountain bike maintenance is a guide that explains what tools you should collect to ensure you can perform any maintenance or repairs on your bike at home to save costs. 

Make sure that the handlebar diameter is compatible with all other components of the mountain bike including the clamp.
Mountain bike handlebars often have the diameter printed on the bar to ensure there are no compatibility issues. Image source:  Amazon.

Related articles:

How to choose the best mountain bike accessories

These are the two methods used to measure the diameter of a mountain bike handlebar:

Method 1. The Caliper Method

As implied by the name, this method involves the use of the caliper and is the easiest way of measuring the diameter of mountain bike handlebars. The caliper is used to measure the diameters of the clamp and grip areas. As this article from the proceedings of The Human Factors and Ergonomics Society Annual Meeting explains, a handlebar grip that is not the correct size for the rider can affect comfort and overall riding satisfaction, not to mention the injuries that can result from an incorrectly sized handlebar. Check out our guide to handlebar width to see what width will work for you.

To measure the mountain bike handlebar clamp diameter, place the widest point of the clamp inside the caliper’s jaw. Make sure the caliper is tight and the jaws of the caliper are pressed flat on the opposite sides of the clamp area. The value measured by the caliper is the clamp area diameter. A digital clamp like this will give you the most accurate measurement and ensure a perfect fit. 

Measure the handlebar clamp diameter of a mountain bike by placing the widest area of the clamp inside the caliper’s jaw.
To measure the clamp area diameter, place the jaw of the caliper on the widest point of the clamp. Image source: ParkTool.

The next step involves measuring the grip area diameter. To do so, place the caliper around the grip area of the handlebar. Aim for the area next to where the brakes get attached to the handlebar, and where you normally place your hands when riding.

Ensure that the caliper is placed flat on the grip area, then tighten the jaws and measure. The value is shown on the caliper grip area diameter.

Place the caliper over the area of the handle where the grip would go to measure the grip diameter.
To measure the grip area diameter, place the caliper on the area where you place your hands. Image source:

Method 2. The Paper or String Method

This method is an alternative for riders who do not have access to a caliper. You will need paper or string like this, a pen, and a ruler or tape measure like this. Though this method may not be as accurate as the caliper method, it is still a useful way of measuring the diameter of mountain bike handlebars.

Simply wrap the paper or string around the center of the grip and clamp areas. Ensure that the paper or string is wrapped around tightly and that there is no slack. Then use a pen to mark the point where the tape or string overlaps.

Measure the clamp width by wrapping the paper or string around the area where the clamp will grip the handlebar of the mountain bike.
Tie the paper tightly around the clamp or grip area. Image source:

After you mark the point of overlap, use a tape measure or ruler to measure the distance from the end of the piece of paper or string to the marked point. This distance is the circumference of the clamp or grip area. To get their respective diameters, divide the circumference by pi  (𝞹 = 3.142).

To ascertain the necessary handlebar clamp width measure the part of the string that fits around the handlebar of the mountain bike.
Measure the distance from the end of the piece of paper or string to the marked point. Image source:

Mountain Bike Handlebar Clamp Sizes

To determine the compatibility of handlebars, one can measure the mountain bike handlebar clamp diameter using various methods. The obtained diameter value can then be compared to the table below to identify if handlebars with the corresponding diameter are still in production or have existed. 

While there are multiple sizes of clamps used in mountain bike handlebars, the two most common sizes are the 25.4mm clamp and the 31.8mm clamp. The 25.4mm clamp is the ISO standard used on most mountain bike handlebars, while the 31.8mm clamp is becoming more popular.

Apart from the 25.4mm and 31.8mm clamps, there are other sizes of clamps. See the table below for handlebars that exist or have existed, and on which types of bikes they are or were used.

Summary of Mountain Bike Handlebar Clamp Sizes

Mountain Bike Clamp Sizes Description of Their Usage Example Product
22.2mm This size is used on handlebars of old MTB and BMX bikes Bicycle Clamp, Durable Aluminum Alloy Bike Shifter Clamp 22.2mm
23.8mm This size is no longer in use. It was common on old British road bikes Knog Oi Bike Bell - Original & Luxe Styles, Built-in Cable-Clip
25mm This size is no longer in use. It was the standard clamp size for old french bikes N/A
25.4mm Standard ISO size for most bike handlebars Wake 25.4 Stem 32mm 60mm Mountain Bike Stem Short Handlebar Stem
26mm This size is no longer in use. It was the standard clamp size for Italian road bikes N/A
26.4mm This size is no longer in use. It was common on old Italian handlebars N/A
27mm This size is no longer in use but was commonly used on titan handlebars N/A
31.8mm This is the size of oversized handlebars and is becoming popular for road bikes and MTB’s 31.8 Stem 45mm Bike Stem Wake Mountain Bike Stem Short Handlebar Stem 
35mm This size is the Easton standard used for mountain bikes with flat bars Spank Spike + Race 2 Stem

Comparing the 31.8mm and 35mm Handlebar Clamps

Handlebar clamps come in various widths that have changed and evolved over the years. 

When comparing the 31.8mm and 35mm handlebar clamps, the latter is wider, stiffer, and stronger, providing increased steering control. However, 35mm clamps can be expensive, hard to find, and are not as widely used as the 31.8mm clamps, which are more commonly found in mountain bikes. 

According to this article from Knog, the 25.4mm and 31.8mm clamps are the two most common mountain bike handlebar sizes. While the 31.8mm is already a wide clamp size, the even wider 35mm clap is becoming increasingly popular.

35mm Clamps are great for supporting heavy-weight riders. If you are a heavier rider who values control then go for handlebars with a 35mm clamp size. If, however, you are lighter weight or want to save money, go for handlebars with a 31.8mm clamp size. Our comprehensive guide to mountain bike drop weight and how it affects handling and steering will help you understand the importance that weight plays when riding. 

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