Bike Size Scaling Chart

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!

  • Sretsok

    Is it cool if we put whatever kind of bike in here, or are you trying to keep it more to touring/bikepacking bikes?

    • hobocross

      I would love it if I could get some help getting other kinds of bikes into the database! There are so many road/mountain bikes that I almost don’t know where to begin. At some point I’ll have to add some categories beyond the pretty vague drop/flat bar type.

  • Alexander Sollie

    I’ve shamelessly ripped off some of your graphing methods as best I could in Google Sheets. So far I only have XL and XXL bikes, but my database is now in one giant sheet so it could be merged with yours some day.

    • hobocross

      Hey man! Good to hear from you and crazy timing. I just put up a new post with your BB-HT angle calculations. I’ve been sitting on this for a couple months and finally thought it couldn’t wait any longer! Let me know if you have anything you want to add to that article. I’ll take a look at your updates and see what we can do about merging our data.

      • Alexander Sollie

        Nice post! I love what you’re doing with this site. Its like if FiveThirtyEight and Vice had a baby that was really into bikes. Digging your instagram too. If you’re interested in getting some more posts on your site I could write some stuff about bikes for tall people. Let me know, and no worries if you’d rather no get into that.