Bike geometry 101 WHY YOU NEED TO LOOK BEYOND THE GEOMETRY CHARTS

To wrap up our series on geometry, we're going to explain why you shouldn’t rely on the manufacturers to get it right, and how to gather your own data

- Alan Muldoon and Danny Milner

As we all know, buying clothes is not an exact science. One pair of jeans with a 32in waist can be tighter or looser than another pair with the exact same measurements. And while you can go into a shop and try clothes on, you can’t do that with something that is sold exclusively online. Taking a punt on a new outfit online can be a gamble. It’s no different when buying a new bike, whether from a bike shop or off the web, and even with the best returns policy in the world, making a mistake quickly becomes a huge hassle.

Obviously the best approach is to go to a good dealer or attend a demo day and physically try the bike. If that’s not possible the next best option is to make an educated guess about how a bike is going to ride and fit based on its geometry. How do you do that? First, you need to read the previous two parts in our Geometry 101 series. In part one we explain how all the different aspects of geometry affect handling through the lens of weight distribution. In the second part, we cover different ways to manipulate bike geometry, from fitting angle-adjust headsets to mixing and matching wheel sizes, all to achieve the numbers and handling you desire.

In this, part three, we’re going to take a deep dive into reading manufacturers’ claimed geometries and why they rarely translate into real-world numbers. Every brand publishes a sizing guide and a geometry chart to go with each model, but just how accurate are they?