What is Size?
Historically, there were three common ways of measuring the size of a bike:
More recently, compact frame geometry (shortening the seat tube while keeping the same functional geometry of a bike in terms of fit and handling) has made it difficult to compare the size of bikes with differing designs. For example, a compact-geometry bike with a 52cm seat tube could fit the same as a classic-geometry bike with a 60cm seat tube.
In response to this inconsistency, some brands report the “effective” seat tube length as if the seat tube extended up to the point where it would intersect an imaginary level top tube.
Increasingly, the trend is for brands to move to a descriptive, nominal sizing scheme such as “Small, Medium, Large, etc…”. However, this approach is also not standardized, so one brand’s Large may fit like another brand’s Medium and so on.
Why does it matter?
The state of bike sizing today is quite fragmented and can be confusing at best and misleading at worst. A brand’s Size description is necessary for us to refer to a specific bike geometry but it’s not a good solution for accurately conveying and comparing the sizes of bikes.
Feeling overwhelmed by sizing? The Bike Insights Compare view is a great way to cut through the confusion and instantly see how the size of bikes differ.