Why is Unbound Gravel mud so bad, how can riders deal with it, and can we predict where the worst sections will be in 2024?

Studying the geology and topography of Lyon County can provide useful information on the location of this year’s sludge.

As Unbound Gravel 2024 approaches, the attention of all concerned is focused on the most favorable weather forecast. Last year’s edition of the biggest gravel race of the year took place in the mud. Sticky, clayey and often impassable sections of mud that started from mile ten and served to clog drivetrains and turn all tires into slicks.

Unfortunately, the forecasts are not very favorable at the moment. The route heads north this year, something it only did in 2019 and 2021, both of which were run in the dry. Kristi Mohn, Marketing Manager of Life Time GP, says:

“The mud of the north is different from the mud of the south. That’s not to say there isn’t mud, but it’s just different. It doesn’t stick as much. The north course holds water a little better, but if it rains you’re riding on gravel roads, and that’s only part of the problem.

While this will no doubt reassure runners, especially given the forecast, the end of this one seems somewhat resigned to the fact that if it rains, there will be mud. Why, then, is the mud in Unbound so horrible? The secret lies in the local geology.

It’s the clay that’s the real villain here.

Clay, not mud

I won’t bore you with too much technical information. I’m a geologist by training, and even with an unnatural love of rocks, the intricacies of sediments make for soporific reading. The bottom line is that the local geology of the Unbound route, whether it is the north or south route, is to a large extent composed of clay-sized particles or true clay minerals.

While you might think of clay as a colloquial term for that material that local artisans use to make expensive mugs to sell at farmers’ markets, it’s also a size; the finest fraction of any sediment, located below silt, and significantly finer than sand. A clay particle is less than 0.002 mm, which is essentially too small to understand. The bedrock of Lyon County is a mixture of shales and limestones, both of which are themselves made up of an unfathomable number of tiny clay particles.

When these rocks weather over millions of years, they break down into their constituent elements and the surface deposits are therefore incredibly rich in clay.

Clay, as all the local artisans who make expensive mugs for farmers’ markets know, holds water incredibly well. An extreme way to think about it would be to think of pouring a glass of water into a handful of beach sand rather than a very clay-rich potting mix – it would flow very freely, a minus. To compound this, some clay minerals absorb water into their physical structure and swell in the process, meaning things take even longer to dry.

In addition to retaining water and not overdrying – meaning if the course gets rain the day before, it may still be grimy on race day – it also sticks to itself. You can make a ball of clay (or an expensive craft cup), but try making it with sand and you’ll end up with a pile of sand (or an extremely useless cup). It’s this interparticle adhesion, aided and abetted by water’s surface tension, that makes it so filthy. That’s why it sticks to your bike, drivetrain, etc.

Unfortunately, if it were just clay it might be a little gentler on the bike components, but the small amount of coarser sand-sized particles produced by erosion of the nodules of Extremely resistant flints remain in the clay and make it act like a grinding paste.

The beige deposits forming a lateral Y with Emporia at the intersection are perhaps where the greatest risk of mud will occur.

The influence of rivers

This is going to sound a bit like high school physical geography, but it’s important, especially when it comes to predicting where the muddiest sections will be for 2024. Clay particles are easily transportable because they weigh very little. Low-energy streams and languid, slow, meandering rivers love clay. These rivers also concentrate clay deposits, as anyone who has fished along a muddy stream knows. As the river meanders over millennia, it picks up, sorts and dumps thick deposits of clay.

South of Emporia is the Cottonwood River, and the geologic map shows clearly and clearly where it has meandered in the past. This is also about where the worst of the mud happened, from what I can gather from an armchair perspective.

The northern route does not have to contend with the Cottonwood, but it crosses the Neosho River, which is roughly equal in size and meander, as well as the ominous name “Troublesome Creek” – North American characteristic by the way names like this are always a highlight.

The Unbound bike by Sofia Gomez Villafane

A paint stirring stick is essential for unclogging your bike.

Where will the mud be at Unbound this year?

Without driving the course myself I can’t be sure, but from a geologist’s perspective the north route doesn’t appear to have the same potential for disruptive mud as the south route.

The sections near the Neosho River deposits are completed at mile 7 when you start to climb, and being so close to the start, and with last year’s event in mind, I would expect that if they were truly going to be disruptive, the race organizers would simply bypass them.

Around mile 110 there is a low point at Mill Creek, but it is a much smaller river and its crossing is elevated, meaning you never need to descend to the level some water. There is every chance that crossing one of the countless streams on the route could cause some mud issues, but we hope these issues will be short-lived and not leave riders resorting to long periods of hiking by bike.

The real kicker may be right at the end of the race. At around kilometer 300, just after a small cemetery, runners will return to the Neosho deposits. The route, however, runs along the most northeastern extent of these deposits, and this, combined with the fact that these are busier roads (because they are closer to Emporia), gives me less reason to m ‘worry. Again, I also suspect that after the negative press caused by the mud last year, if these terrains became truly impassable, the organizers would bypass them as well.

challenge gravel crusher tanwall tires

This could be an ideal tread for a muddy Unboubound, but don’t use the cotton sidewalls – flint is sharp!

Can I make my bike mud-proof?

Not mud-proof, but there are some things you can do to make your setup easier. Using thinner tires will allow more mud clearance between the tire and frame/fork, reducing the risk of them being completely gummed up.

Well-cleared tires would also help – Either something with a relatively smooth center or something with widely spaced knobs would do the job well. I have no experience on this terrain, but if I had to ride it I would probably spec something like the Challenge Gravel Grinder.

Pros (and amateurs too) carry a paint stirrer to unclog the bike should the worst happen. Praying for more rain might actually help, as it will help things stay a little smoother. Starting with a nice clean bike and giving the frame a coat of polish (sorry, matte bike fans) will help prevent mud from sticking to it so easily. Be liberal with this, and if you’re in a bind, a rag and GT85 will do a similar job. Just be careful near the brakes.

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