Here’s a look at how the perceived size of a bike (stack and reach) sometimes changes unexpectedly when going up or down a specified size for a particular bike.
This chart is pretty ugly. And we have bike companies to blame (sort of). In an ideal world, there would be a smooth and predictable increase in the stack and reach when going up in size on a bike model. But the reality is that factors like fixed tire sizes and shared tubesets require that stack and reach be tweaked for certain bike sizes.
Sometimes you hit a hard limit where the bike just can’t be made taller without compromises in the triangulation… or can’t be made shorter without needing to go with a smaller wheel size.
Occasionally there is a “break” in the bike model line where a different tire size is introduced and a dissimilar geometry emerges. Sometimes the geometry just doesn’t scale linearly and we could have errors in the geometry charts or database to blame.
At any rate, this is an interesting study before purchasing your bike frame. Consider all the sizes available and consider what you might gain/lose by moving up/down a size. You might be surprised.
Don’t see the bike you’re interested in here? The bike geometry database is currently open for anyone to contribute to. It just takes a few minutes of your time and any additions will be included in the next day’s chart refresh. Try it!