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How to measure the diameter of your handlebar

Knog Oi Bell Size Guide

Handlebars come in numerous styles and sizes, but we’re here to help make choosing the right size Oi bell for your bike(s) easy. After all bell size does matter!

Watch this video to understand where & how to attach your Oi bike bell.

First things first

Most of the time the area you’ll be attaching the bell to, will be either 22.2, 25.4 or 31.8mm and can generally be separated in to the below categories.

  • Road Bike – Handlebars generally come in two clamp sizes 26mm (older style) and the newer ‘oversized’ 31.8mm. The area where you attach the Oi bell will most likely be either 25.4mm or 31.8mm.
  • Commuter/Cruiser Bikes – Handlebar sizes do vary due to the wide variety of styles, however most bar sizes would be either 25.4 or 31.8mm
  • Mountain Bikes – Handlebars generally come in two clamp sizes 25.4mm (older style) and the newer ‘oversized’ 31.8mm. On some bars there will be a bulge in the middle and the bars will thin out towards the brake levers. If you want to attach your bell here, then please make sure you measure as it could mean you move from a large sized bell to a small. For instance the grip area on some of these bars will be 22.2mm, whereas the bulge is 25.4mm.
  • BMX – Always 22.2mm.


  • If your handlebar is any bigger than 22.2mm then you will need to choose the large Oi Classic or Oi Luxe bell. The Larger Oi includes shims that will allow you to attach the bell to bars 23.8, 25.4 and 26mm.
  • If your handlebar in the middle looks 'normal sized', it's probably 25.4mm and you'll need a large bell.
  • If your handlebar looks overly big in the middle, it's probably 31.8mm and you'll need a large bell.

Measuring your handlebar diameter is easy, and can be done using household items if you don't have digital callipers. Here's how...

Use Digital Callipers

The easiest way to measure those handle bars is with a set of digital or vernier scale callipers.

Measure Handlebar
Measure Handlebar


Use Measuring Tape

If you don’t have callipers then you can use a simple measure tape. Just wrap around the bar at the point you want to attach the Oi to get the circumference size and then divide by pi (….mmm) to get your diameter e.g. 99.9mm / 𝜋 = 31.8mm.

Measure handlebar
Measure handlebar


Use Paper, Pen & Ruler

If you have no tape, then use a piece of paper (or string). Same as above, just wrap the paper around the bar at the point you want to attach the Oi, make a mark with a pen where the paper intersects and then measure against a ruler. This will give you the circumference and to get the diameter just divide by pi. Easy.

Measure Handlebar
Measure handlebar

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