Unbound Gravel vs. UCI Gravel: How I'd set up my bike for gravel’s top races

Gravel cycling has officially become a professional sport. Few things highlight this transformation more than the significant investment from major brands in R&D in the gravel space, the competitive salaries some riders earn, and the fact that the world’s top cyclists are vying for a coveted rainbow jersey.

Gravel racing has also sparked a new level of tech obsession, with endless debates over the optimal race setup. For the everyday rider interested in gravel, this can be can be both exciting and daunting. There is no single setup that works for every event—there's always a trade-off depending on the next race. The only constant is that nothing is consistent.

Along with the constant changes and experimenting, every geographical region appears to have its own interpretation of what a gravel course should be like, too. When the UCI entered the gravel space in 2022 with the debut of its UCI Gravel World Series and the first-ever UCI Gravel World Championships, it became clear that its interpretation of gravel differed vastly from the highly popular American events like Unbound Gravel. While mountain bike tyres are trending in Kansas, the first UCI Gravel World Championships was won on a road bike.

To explore this divide and offer some tips and inspiration for your own race setup, we've set out to build the ultimate bike that bridges both styles. Let’s dive in.

The separate technical challenges of American and European gravel racing

To start, let's look at the concrete differences between gravel on the two main continents where it is raced. In North America, where the discipline was founded, gravel racing from adventure rides that offer a wide variety of technical challenges and usually boost some serious mileage. With the exception of but a few races, U.S. gravel races are between 100 km and 322 km (200 miles) in length. (If it is longer than 200 miles, it will likely be considered an ultra event.) Additionally, most of these races are somewhat self-supported, which means nutritional and mechanical support for the riders is limited and sometimes not allowed at all.

In Europe, the expectations are different, especially amongst the UCI Gravel World Series. Born from road racing, UCI gravel races must be between 50 and 175 kilometres (31-108 miles) and can either be a circuit race or a point-to-point race. What’s more, the UCI requires frequent feed zones; races over 90km require no less than three feeding points where riders can receive hand-ups. There are no team cars, and riders are still required to fix their own bikes outside of the aid stations.

Most importantly, gravel roads in North America are vastly different from gravel roads in Europe. Europe is a much more densely populated place, which means the technical characteristics of European gravel races are often quick tight turns, frequent changes of terrain, and punchy climbs. In North America, the challenge comes from rough remote roads, bigger climbs, and the possibility of singletrack. Of course, some European races have long climbs and singletrack, and some American races are punchy and change terrain like some of the European races, but generally, geography does play a role.

Big picture comparison

One of the joys (or hassles) of gravel cycling is all the fine-tuning that goes into a bike setup. More similar to mountain biking than road cycling, gravel encourages bold swings and specific choices in pursuing technological gains.

For this story, we have kept it simple: one frame, one drivetrain and two very different specs to fill out the other details. Our goal was not only to compare two styles of gravel racing, but also to highlight the customisation options that allow you to personalise your bike and build confidence in your race setup, all while keeping it accessible.

Here are the full choices of both builds:

The dark art of tyre choice

Everything we thought we knew about tyre selection for gravel has come under much scrutiny over the last years due to one key change in understanding: narrower tyres are not necessarily faster.

Now, that’s not to say that this is a universal rule. Narrow tyres can be quicker, but it also is not always the case. Many other variables influence the speed of a tyre more than simply the millimetres of tyre volume.

In gravel racing, tyre choice may just be the number one pre-race topic, as the choice is extremely course-dependent. Even in these huge U.S. versus UCI race generalisations that I'm making, naming a specific tyre to use for each category would be counterproductive. What I can offer, however, is two alternatives that optimize a gravel bike for either end of the gravel spectrum, assuming the UCI gravel racing is on the tamer end of the scale and U.S. gravel racing is more on the gnarly side.

For UCI racing, with its shorter distances, often controlled lap environments and significant portions of pavement, riders might favour a slick tyre with dramatically more volume. As mentioned earlier, narrower is not faster, but rubber construction and thread count (TPI) do. For me, this theory has rang true with the tyres I've been testing, including the Snoqualmie Extralight tyre from Rene Herse as featured on my build.

Built with a high thread count and weighing just 335g, the Snoqualime Extralight is as fast as it is supple. It creates a dynamic contact point that manages the suspension losses that slow other tyres down. It is 44mm wide, which is very large, but it still retains a decent shape on modern wheels.

The combination of the lightweight, slick tyres and deeper-rimmed road wheels creates a great ride that is fast on the tarmac, agile around corners both on and off the road, and surprisingly smooth when the going gets a bit rougher. That combination is key to the difference between all-road and gravel, but in a relatively smooth off-road environment without large or sharp rocks, it’s undeniably fast.

On many American courses, however, the extra light construction of the Rene Herse tyres is not the right choice, even with its 44mm of width, because everything that makes it fast also makes it susceptible to punctures. There are higher durability casings available from Rene Herse, however these do come with a compromise on weight, suppleness and speed. More and more, riders are looking for a solution that retains the same pliable construction and adds volume to create a system with low suspension losses and more flat prevention.

The most visible example of this is the popularity of a new Maxxis mountain bike tyre that some of the biggest names in U.S. gravel are using. Both Keegan Swenson and Payson McElveen have leaned into the 2.25-inch wide Maxxis Aspen ST tyres. By all accounts, this isn’t just a sponsor-driven stunt, especially as the likes of Lifetime Grand Prix athlete Dylan Johnson had doubled down on his position that all gravel races should be run on tyres that are two inches or wider.

If your bike has clearance for such beefy tyres, they do make a lot of sense. On the road, there may be a difference to the sound of the tyre – with its width and small knobs creating both wind and ground noise – but the speed actually only drops on sustained climbing. Off-road, it changes everything as the width and high thread count are incredibly smooth in a straight line. Around technical features, tight turns and rough roads, the tyre is a huge upgrade in comfort and speed versus the slicks mentioned above.

A note about wheel choice

When running big tyres, the wheel choice is one where there are a few different directions to go. Unlike the UCI build, where slick 44mm tyres can be paired well with deep and wide road wheels, factors like aerodynamics and weight become more murky when working with mountain bike tyres.

From an aerodynamics perspective, the newest gravel wheels, like Zipp's 303 XPLR and Parcours' FKT wheelset, would theoretically be faster. Even with the 2.25-inch tyre width being well over the 105° rule that has typically governed wheel-tyre aerodynamics, which states that the rim must be at least 105% of the width of the tyre to gain aerodynamic benefits.

But deep wheels do have trade-offs, especially when riding over gravel. Cross winds, for instance, can be much more impactful on uneven surfaces of racing. Additionally, adding more rim weight to a relatively heavy wide tyre can change the handling and acceleration. To understand these trade-offs, it is good to look at the pro athletes and what they choose to use at big events. At SBT GRVL, for example, the aforementioned big-tyre fans McElveen and Swenson (who won the race) paired the Maxxis Aspen ST tyres with moderately deep rims. However, McElveen, who is a Zipp-sponsored athlete, chose to run a 303 Firecrest instead of the new XPLR wheels.

After some consideration, I opted to spec my U.S. gravel build with the fairly neutral Shimano GRX WH-RX880 carbon rim. The Shimano offerings are affordably priced for a carbon set, with a moderate outer rim width of 30.7mm, inner width of 25mm, a depth of 32mm, and a total weight of 1,397 grams for the wheelset. If budget weren’t an issue, I might opt for a different wheelset with a 30-40mm depth, however, these dimensions offer the best balance of feel and performance when paired with the large Aspen ST tyres.

Geometry differences

Saddles are one bike component that people rarely change. Even if the type or model of saddle may change from time to time, where that saddle sits is normally fairly locked in. But should it be?

One of the less obvious changes I made on my two bike builds was swapping the seat and seatpost. For the UCI build, the seatpost is a Vision carbon post with 25mm of setback paired with a Fi’z’i:k Terra Argo saddle. For the U.S. build, the seat post is a Vision model with 0 mm of setback paired with an Ergon SR Tri Men Mid Titanium saddle.

I chose the Fi’z’i:k saddle and setback post combination for the UCI gravel build since it is the more traditional fit that distributes the rider's weight neutrally between the front and rear wheels of the bike. This fit is best for riding on drop bars on technical courses as it puts more weight on the rear wheel to gain traction around slick turns. In a pack environment, it also always quicker shifts in weight to produce more agile handling. It is a position that would be closest to what a road racer would want for a short, punchy road race.

The Ergon saddle and straight seatpost were an effort to have a position that is built around a progressive, aerodynamic position borrowed from triathlon racing. The Ergon saddle, in particular, is built around triathletes trying to sit on the front of their saddles for extended periods of time. The same demands are common in U.S. gravel racing due to the long duration of the races, paired with the tendency for the packs to blow to smithereens in the first hour, which means you might find yourself alone without a peloton to draft from.

Naturally, there are physical limitations to what riding position you may be able to adopt, but it's worth considering different saddle and seatpost options for different types of efforts. Just like tyre choices and gear ratios depend on the course, your weight distribution and ergonomic preferences can have a similar impact on your ride.

Recognising the element of uncertainty

The final big variable that changes the setup between UCI gravel and U.S. gravel is how the two sides of the sport interact with uncertainty or unpredictability. This, again, relates to big point-to-point races in the U.S. versus the tamer circuit races the UCI puts on. Simply put: the more you know, the bigger swings you can take.

The first area where uncertainty plays a role is in gear choice. In UCI racing, punchiness and speed are key. On road-heavy courses, having big gears and small jumps between the cogs is beneficial in the effort to hold the wheels, stay in the pack and conserve energy for all the micro-efforts that go into a race. That’s why the UCI build sports a 50t chainring from Garbaruck (I have it on an older Quarq five-bolt spider as it is still the simplest 1x power system for swapping chainrings) and a 10-45 Shimano cassette to pair with the Shimano 1x mechanical groupset I have been testing this summer.

While 50t might seem like a big gear for gravel, the size of the chainring offers a huge benefit to the overall drive-chain efficiency. More teeth mean watts are saved through the gained leverage and efficiency of the system – just take a look at the WorldTour time trial setups, and you will see the pivot toward big rings across the board. The same science applies to gravel.

The biggest barrier to running a huge chainring is the fear that you may run out of easier gears somewhere along the course on an important pinch point. Generally, the rule of thumb is to select a gear that will put your chain towards the middle of the cassette for the majority of the time.

In U.S. gravel, that kind of certainty is less easy to find. Courses are not always available to preview, and even if they are, most people don't have time to go scout a 200-mile course. The surface type and condition may also change the gear needs as does the tyre choice. Smaller chainrings are often used with larger tyres because the increase in tyre diameter covers more ground per pedal rotation. By using smaller chainrings, you can maintain a manageable gear ratio, making it easier to pedal despite the larger overall wheel diameter.

Other risks that can be taken when a course is well-known are shoe and pedal choices. In a vacuum, road pedals and shoes are objectively faster. The shoes are more aerodynamic, the contact point between the cleat and the pedal is more solid, which offers a more efficient power transfer, and they are often more breathable, which increases comfort.

But in gravel, there is always a trade-off. As soon as you have to step off the bike, whether it be for mud, avoiding a crash, or walking a particularly technical section, those efficiency gains of road cleats are quickly negated. A good pair of mountain bike or gravel-specific shoes will still have a stiff but walkable sole and traction pads and are, therefore, a better bet if there is any chance of having to dismount.

The universal pieces of kit

Even with the separate characteristics of the races, there are a few common pieces of kit used for gravel races on both sides of the Atlantic. First and foremost: aerodynamic handlebars.

From the outside, this might seem like an arbitrary place to start, but strip away everything else, and the aerodynamic gains from swapping out standard round bars for a more aerodynamic option will always be a benefit. It is one of the few items where there are undisputed gains regardless of rider position, tyre width and frame. The front of the handlebars and how they interact with the wind always matter. Additionally, a well-constructed one-piece bar-stem combination can also improve the ride feel as the shape and cohesive construction can help dampen the road vibrations and offer a small but tangible benefit to the system’s compliance.

The tendency for gravel races to use number plates on the front of the bike does make bars aerodynamics less important, however, there are ways to mitigate that. And I do believe it's upgrade worth considering.

The second universal piece of kit is bottle cages. Bottle cages seem fairly insignificant, but ask any rider who has been at it long enough and they will tell you a horror story about losing a bottle or two due to failing cages. In endurance races where self-sufficiency and nutrition are paramount, cages should never be an afterthought.

The risk of bottle ejection aside, cages can also give you more flexibility for bottle sizes and position. For example, the King Cage steel cages pictured above lower the bottle position, leaving room for a frame bag while still holding tall bottles for hot races.

The third and final universal piece of kit is a saddlebag. Regardless of where you are in the world, if you flat your tyre, you must fix your tyre. Integrated downtube storage covers some of the gear, but to be fully prepared (with things like a tube, derailleur hanger, quick link, and replacement valve core — all things that I have used this year in races), a trusty seat bag is a must. Many of these are light and fairly aerodynamic, as you can see from this Orucase option, which is my personal favourite gravel saddlebag.

* Logan Jones-Wilkins is a freelance journalist and gravel racer who is a long-standing contributor with Rodeo Adventure Labs. The Trail Donkey 4.0 pictured here is Logan’s personal bike and is merely the vehicle for the rest of the story.