Often people will recommend a certain gravel tire based on terrain you ride. But that's only half the story.

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 a few 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.

Recommended gravel tires for Exploro RaceMax

Because WAM depends partially on the inner width of the rim, you might want to use a different tire on a different rim. This is not only important for tire fit but also for its performance. A very wide tire on a narrow rim is very flexible sideways, meaning that in corners your handling won’t feel as secure. So as you move from road tire widths (28-35mm) to real gravel widths (35+mm), it pays to also look for a wider rim.

As the WAM changes, so does the RAM. This is not so critical in most cases, but in the case of the Exploro RaceMax where we try to optimize the clearance between the tire and the seat tube cutout, we do target a specific RAM for optimal performance. We recommend the tires below based on:

  • WAM & RAM
  • Tire profile
  • Casing design
  • Rolling resistance (keeping in mind the profile)
  • Puncture resistance (keeping in mind profile & weight)
  • Aerodynamics (this one is tough as we can’t put every tire in the wind tunnel)

Please note that while WAM & RAM measurements are more accurate than the dimensions on the tire label, there are still variations:

  • While inner rim width is the biggest rim factor, the exact shape of the rim bed and depth of the flanges also affects the shape and size of the tire mounted.
  • Tires vary due to production conditions, so two tires from different batches may size differently. That means an individual tire’s RAM may be off by a few mm (much less for WAM), and that is a lot when you’re trying to create a proper fit between tire and seat tube. So with WAM and RAM, we’ve gotten closer to a solution but we’re not 100% there yet.

Always check for sufficient clearance between the specific tire you use and your bike frame irrespective of WAM & RAM listed here