What size is my gravel tire anyway?
What it most likely is NOT is what it says on the label. To understand why and learn about WAM (Width as Measured) and RAM (Radius As Measured), read it here.
So which tire do I need?
The gravel tire you need depends on 3 main factors. People often focus on the terrain, for example by defining 3, 6 or 20 types of gravel and then recommending the perfect gravel tire for each. But that ignores a major factor: the rider.
The rider has (or doesn’t have) certain skills to keep the bike under control and avoid flats. The rider also determines the speed. The winner of Dirty Kanza may use 35mm tires, but if I use the same tires, I will likely end up walking for miles. Especially if it’s wet and my slower speed sees me sinking into the mud more than the faster rider who floats over it.
Furthermore, roots, rocks and cracks get smoothed over more at high speed than at low speed where you really bump into everything. This image explains it:
Taking into account both terrain and speed, the graph of suggested (gravel) tire widths looks something like this (it’s just an indication, don’t get too hung up on a mm here or there). And again, if you need a refresher on WAM, just check it here.
Spoiler: the front derailleur
It’s important to note that when using a 2x setup, the front derailleur will often interfere with the width of the tire before the frame does. The front derailleur clearance is fairly constant independent of which frame you choose, as the derailleur is always set up a certain distance from the center plane of the frame. This means that at a certain point, if your 2x setup interferes with your rear tire, you only have three options:
- Change the front derailleur to something with more clearance (mechanical always has more clearance. Other than that, SRAM WIDE AXS has more clearance than regular, and Shimano GRX more clearance than Shimano road groups)
- Change to a 1x setup. No front derailleur always gives you more tire clearance
- Change the tire.
Changing the frame won’t really change the outcome in a significant way, unless you have a frame with a crazy long chain stay so the front derailleur sits in front of the tire instead of next to it. But then you have a frame that won’t handle well, so that’s not really an option either.
Recommended gravel tires
After taking these hundreds of tire measurements, we thought it made sense to recommend those we like best for grip, puncture resistance, fit and aerodynamics. To learn more, check out:
Best tires for Racemax 418 & Ultra