Lessons from 50+ years in the saddle.
What Tire Size Should I Run on My Gravel Bike? Lessons from 50+ Years in the Saddle
I’ve been riding bicycles for over 50 years, and I’ll tell you something: the question of tire size has never mattered more than it does in gravel cycling. When I started building frankenbikes for gravel riding back in 2007—long before “gravel bike” was even a category—I was trying to figure out what worked through pure trial and error.
These days, I ride a Rodeo Labs Flannimal with 42c tires, and I’ve landed on that size after years of experimenting on Colorado’s diverse gravel roads. But here’s the thing: the “right” tire size isn’t universal—it depends on your terrain, your riding style, and what you’re willing to compromise.
The Tire Size Sweet Spot (Spoiler: It’s Probably 40-42c)
Looking at discussions in the gravel cycling community, I see riders constantly debating between 38c, 40c, 42c, and 45c. Here’s what I’ve learned:
38c tires are fast on hardpack and pavement, but they’ll beat you up on chunky Colorado gravel and won’t give you much confidence when things get loose. One rider in the community mentioned wanting to go from 38c to 40c on their Orbea Terra—and honestly, I’d tell them to make that jump if they can.
40-42c tires (my sweet spot) offer the best balance for mixed terrain. They’re fast enough on pavement that you won’t feel sluggish on the connector roads between gravel sections, but they have enough volume to smooth out rough surfaces and give you traction when the road turns to washboard or loose rock. Out here in Colorado, where you might start on smooth dirt roads and end up on technical doubletrack, this range handles it all.
45c+ tires are approaching mountain bike territory. They’re great if you’re riding gnarly terrain or want maximum comfort, but you’ll pay for it in rolling resistance on faster sections. I see riders running Thunder Burt 2.1s (roughly 53mm) and loving them—but that’s a specific choice for specific terrain.
What Your Frame Can Actually Fit
Here’s a reality check from someone who learned this the hard way: your frame’s maximum tire clearance isn’t just about fitting the tire between the chainstays.
You need to consider:
Mud clearance – In wet conditions, Colorado clay sticks to everything. If your tire is already close to the frame, you’re going to have problems.
Tire measurements are lies – A “40c” tire from one brand might measure 42mm on your rim. A 42c from another brand might be 44mm. Always check actual measurements, not what’s printed on the sidewall.
Rim width matters – Wider internal rim widths make tires measure bigger. My Flannimal can technically clear more, but I stick with 42c because it’s predictable.
The Real Question: What Are You Actually Riding?
After 18 years of gravel riding, I’ve learned that tire size should match your worst terrain, not your average terrain. Here’s my breakdown:
If you ride 80%+ smooth gravel and pavement: 38-40c is plenty. You’ll appreciate the speed.
If you mix pavement, gravel, and occasional singletrack: 40-42c is the goldilocks zone (where I live). You’re not giving up much speed, but you’re gaining real capability.
If you’re riding technical terrain, loose surfaces, or prioritizing comfort: 42-45c+. Accept that you’ll work harder on pavement, but you’ll have more fun everywhere else.
Pressure Matters More Than You Think
One thing I see new gravel riders miss: tire size and tire pressure work together. I run my 42c tires tubeless at 28-32 PSI depending on conditions. That volume at lower pressure is what gives you the magic—the comfort, traction, and puncture resistance that makes gravel riding so good.
A 38c tire at 40 PSI will feel harsh and skittery. A 42c at 28 PSI feels like you’re floating over the same terrain. The bigger tire lets you run lower pressure safely.
Which Tires Should You Actually Buy? (And Which Ones to Avoid)
After talking to hundreds of gravel riders and testing tires myself over nearly two decades, I’ve seen some clear patterns emerge. Let me save you some money and frustration.
Tires I’d Avoid:
WTB (with one exception) – I know they’re everywhere, but I’ve heard too many consistent complaints about WTB tires to recommend them. The Nano, Horizon, and Byway in particular get criticized for difficulty sealing tubeless (weeping sidewalls are a common complaint), poor puncture resistance, and rubber compounds that feel hard and slippery. I’ve talked to multiple riders who sold their WTB tires after just a few hundred miles. The one exception seems to be the WTB Raddler, which gets positive feedback from people who’ve tried it.
Maxxis Rambler – This surprises people because Maxxis makes incredible mountain bike tires. But their gravel offerings? Not so much. The Rambler gets hammered for being draggy on pavement and hardpack while offering poor grip on loose surfaces. The casing quality isn’t there, and puncture protection is mediocre. I’ve seen too many disappointed Maxxis converts to recommend them for gravel.
Some Schwalbe models – While Schwalbe makes excellent tires in many categories, I’ve heard from high-mileage riders that some of their gravel tires wear too quickly. If you’re putting in serious miles, this matters.
Tires That Actually Work:
Specialized Pathfinder Pro (42mm) – This is my current favorite, and I’m not alone. The 42mm width (I run the tan sidewall version) is a genuine goldilocks tire—fast enough on pavement, capable on gravel, good grip, and it sets up tubeless without drama. The only complaint I hear is that they’re frequently out of stock, which tells you something about how many people love them. If you can find them, buy them.
Pirelli Cinturato (H and M variants) – These have become my go-to recommendation when I can’t find Pathfinders. The H (harder compound) works beautifully for fast, mixed terrain riding. The M (medium compound) offers more grip for technical sections. The quality is there, and they feel like premium tires.
Schwalbe G-One R and RS – If you’re looking at Maxxis and want something better, look here instead. Better rolling speed, better grip across varied terrain, and the build quality you expect from Schwalbe.
Tufo Thunderos and Speederos – I’ve talked to several riders who switched from other brands to Tufo and reported massive improvements in performance, particularly in puncture resistance and overall ride quality. Worth considering if you’re tired of dealing with flats.
The Bottom Line on Tire Choice
The gravel tire market is full of overhyped products that look good on paper but fail in real-world use. Don’t assume that a brand’s mountain bike reputation translates to gravel—it often doesn’t. And when a tire is consistently out of stock (like the Pathfinder Pro), there’s usually a good reason: it actually works.
My advice? Start with proven performers like the Pathfinder Pro or Pirelli Cinturato line, get them set up tubeless, and dial in your pressure. Save the experimentation for after you know what good feels like.
What I’d Tell My Younger Self
If I were starting over today, I’d do exactly what I’m doing now: build around 40-42c tires and run Pathfinder Pros or Pirelli Cinturatos. It’s the most versatile choice for real-world gravel riding where you never know exactly what you’re going to encounter.
Don’t obsess over having the absolute maximum clearance “just in case.” I’ve seen riders with frames that clear 50mm running 38c tires because that’s what works for their riding. And I’ve seen riders maxing out their clearance at 42c and being perfectly happy.
The best tire size is the one that matches your terrain and gives you confidence to ride harder. And the best tire brand is the one that actually delivers on its promises.
After 50 years on bikes and nearly 20 years on gravel, I can tell you: the difference between 40c and 42c matters way less than choosing good tires, setting them up tubeless, and getting the pressure right.