Article: Your Tire Choice Could End Your Race. Choose Right.
Your Tire Choice Could End Your Race. Choose Right.
Unbound isn’t a gravel race. It’s a 200-mile survival test disguised as one, and the Flint Hills don’t bluff. Those sharp, arrowhead-grade flint rocks have ended more races than bad legs ever will. Forget your power numbers. Forget your nutrition plan. If you roll into Emporia on the wrong tires, you’re already gambling with a DNF.
We’ve been building gravel tires for riders who take the Flint Hills seriously. Here’s exactly what to run and who it’s built for.
Know Your Course Before You Choose Your Tire
The biggest mistake riders make is picking a tire without accounting for one variable: which course are you on?
The South Course is flatter, faster, and more forgiving. Riders pushing for time can lean toward speed-biased setups. The North Course is the animal: rougher roads, larger rocks, deeper ruts, and terrain that punishes anything underprepared. When the weather turns (and at Unbound, it always turns), the calculus shifts even further toward grip and durability.
Know your course. Know the forecast. Then pick your tire.
The WTB Unbound Lineup. Built for Every Rider, Every Condition.
Vulpine S. For the podium hunters on dry days.
If you’ve pre-ridden the course, you know the conditions are fast, and you’re chasing a result. This is your tire. The Vulpine S runs a fully continuous slick centerline, pushing rolling resistance as low as we can get it while the tightly packed side knobs keep you planted through high-speed corners.
It’s a specialist tool. When conditions are right, it’s the fastest thing we make. When conditions go sideways, the Vulpine S demands respect from the rider.
Best for:
- Chasing podiums to PRs
- Dry, hard-packed conditions
- South Course speed runs
Sizes:
- 40mm, 45mm with SG puncture protection
Vulpine. The all-day workhorse.
The Vulpine is what most riders at Unbound should be on. Tightly spaced center knobs form a near-continuous rolling surface without going full slick, and the shoulder knobs provide predictable bite when you lean into chunky corners or hit the brakes later than you should have.
It’s not trying to be the fastest tire on the line; it’s trying to get you to the finish line. There’s a meaningful difference.
Best for:
- Riders who want speed without all-in commitment
- Mixed forecasts
- Front/rear combos
Sizes:
- 40mm, 45mm with SG puncture protection
Raddler. The gap most riders are missing.
Here’s the tire that doesn’t get enough credit at Unbound: the Raddler. Tightly packed center knobs with taller, more aggressive side knobs put it between the Vulpine and the Resolute; faster than a full mud tread, grippier than a near-slick when the loose stuff shows up. If you’re running the North Course, riding through changeable weather, or you want a tire that can eat up technical terrain without giving up too much time on the flats, the Raddler hits the sweet spot.
It’s the tire for riders who won’t commit to saying conditions are “fine.”
Best for:
- North Course riders
- Unpredictable weather
- Anyone wanting rear traction without giving up speed
Sizes:
- 40mm, 44mm with SG2 puncture protection
Resolute 42/Resolute 50. When the course gets savage.
When Unbound goes bad – mud, standing water, rocks the size of softballs – the Resolute is what’s still moving. Widely spaced square knobs dig in and shed debris, the tall knob height finds traction where other tires just spin, and the generous volume absorbs the kind of chatter that destroys your confidence and your legs by mile 80.
Elite racer Whitney Allison proved that point at Unbound 2025 where she rode 200 miles on Resolute 50 SG2s and crossed the finish line in 14th overall, without a single mechanical. That’s not an accident. That’s what a tire engineered for exactly this race can do.
The 42mm is the workhorse for riders who want aggressive grip in a manageable package. The 50mm is for those who want maximum volume: lower pressures, more float, and more forgiveness over the worst terrain Emporia can throw.
Best for:
- North Course in bad weather
- Wet, brutal, or unpredictable conditions
- Riders who cannot afford a mechanical
Sizes:
- 42mm, 50mm with SG2 puncture protection
Nano 52. For riders who want the kitchen sink.
The Nano 52 is for Unbound riders who want everything: speed, volume, stability, and the confidence to pin it over rough terrain without second-guessing the tire under them. At 52mm true width, it floats over chatter, runs comfortably at low pressure, and still rolls efficiently enough that you’re not dragging an anchor through the fast sections.
If your bike clears it and your priority is comfort over the long haul, especially for the 200-mile distance, the Nano 52 is a legitimate weapon.
Best for:
- Max comfort seekers
- Bikepacking-adjacent setups
- Riders prioritizing finishing strong over finishing fast
Sizes:
- 52mm with SG puncture protection
How to Actually Pick
Stop treating tire selection like an afterthought the week before the race. Here’s a simple framework:
|
Condition |
Recommended Tire |
|---|---|
|
Dry, fast, experienced racer |
Vulpine S front + rear |
|
Mixed or unpredictable |
Vulpine front, Raddler rear |
|
Technical or North Course |
Resolute 42 or 50 front, Vulpine or Raddler rear |
|
Wet, brutal, or survival mode |
Resolute 50 front + rear |
|
Max comfort, full distance |
Nano 52 front + rear |
One more thing: whatever you run, run it tubeless. Add fresh TCS Sealant a day or two before the race. Check your pressure the morning of. The Flint Hills will test every variable; make sure your tires aren’t one of them.
The Bottom Line
There’s no wrong tire if it matches your race. There are only wrong choices made without enough information.
We’ve had athletes finish Unbound in every condition imaginable on WTB rubber. The tire doesn’t win the race for you, but it can absolutely end it. Pick the one that fits your course, your conditions, and your risk tolerance. Then go make the Flint Hills yours.
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About WTB
Founded in 1982, WTB was formed in Marin County, the birthplace of mountain biking, to design better bicycle products. Renowned for saddles, tires, rims and grips, this rider-driven company continues to push the boundaries of what’s possible through an unrelenting spirit of innovation and passion for two-wheeled adventure.
