Core4 Gravel 100 Mile: B-roads, Urban CX, & Corn Sweat
Core4, now in its fourth year, is part of the 2025 Gravel Earth Series. The route connects the four ‘quadrants’ of Iowa City by way of an urban network of bike paths and singletrack along the Iowa River. While still mainly rural gravel roads and unmaintained B-roads through rolling hills and cornfields, this adds a unique urban cx vibe.
The evening before race day a massive thunderstorm came through and dumped a lot of rain in a short time. Flooding was expected and an updated ‘wet’ route was sent out that eliminated the singletrack along the river. At race packet pickup that evening at Wilson’s Orchard, the venue that was hosting the start/finish and pre- and post-race parties, thunder still rolled in the distance and the dusk sky was illuminated with brief flashes of lightning when I arrived.
Saturday was expected to be one of the hottest days of the summer for Iowa City with a high of 93. All the rainfall meant that an already hot, humid day would turn into a sauna, especially riding through the corn fields and areas with heavy vegetation. Plants seemed to radiate heat, a phenomenon called evapotranspiration, or “corn sweat.” August 16 turned into an intensely hot race day with no shade, very little wind, and a heat index topping out at 114.
But the morning started out in the high 60s with scattered showers and that beautiful open soft light that you see in the midwest. The pro/elite fields started at 8(men) and 8:15(women) and it was exciting to see riders like Lachlan Morton, Adam Roberge, Rosa Kloser, Gee Schreurs, Sarah Sturm, and Karolina Migon lining up. Amanda Nauman Sheek live streamed the pro men’s race, and Holy Spirit of Gravel live streamed the pro women’s race. Both were following the race in 4-wheel ATVs, and the excellent coverage they provided via Instagram Stories can be viewed on core4.bike’s IG highlights. (Here is the HSOG podcast on the core4 weekend.)
The Open 100 that I signed up for started at 8:30. The rural gravel roads consisted of climbing or descending 5-7 percent gradients with almost no flat stretches, totaling 4,500ft elevation. Most climbs were short enough that you could maintain momentum from the downhill to get most of the way up. This would prove helpful in keeping momentum towards the end of the race, too.
ON A B-ROAD
At about mile 23 we hit the first of the B-roads. These are unmaintained roads and we were warned of peanut butter mud conditions after rainfall. While green is grip (cx is here, after all), that doesn’t hold true when grass and sticky mud mix, and many of us very quickly found ourselves on bricked bikes. I found a straw and used it like a piece of string to clear the mud from the tires, and was glad yet again for my Crank Brothers Eggbeater pedals. There were seven more B-roads to come, each between one and two miles in length. Though not all of them were muddy, this first one fully strung out the groups. The B-roads were the decisive feature in both M and W’s pro/elite fields.
The course turned back towards the city where we were directed to take care to use the shoulders and bike paths. The route was very well marked but there was so much crossover connecting all the urban pathways that the vibe turned slightly chaotic, especially with the payoff of the much hyped section of 5 miles of flowing singletrack removed. The temps were now in the high 80s and humidity was rising quickly.
At a midpoint aid station I needed to refill my hydration pack and both bottles. The volunteers at the aid stations were really kind and super helpful. They insisted on refilling our bottles and hydration packs for us, and even had pressure washers to clear the mud from the b-roads. This pro treatment by the local community was unexpected and very much appreciated. In total I’d go through 8 liters of fluid including 3 cokes and 3 carb mix bottles.
CORN SWEAT
Around mile 65 about 4.5 hours in my watts were struggling to keep up with my HR and things started to slow down. This was after the last of the urban trail sections but with most of the b-roads still to come. The B-roads would have been a completely different experience if it hadn’t rained the night before. But now, with temps and heat index at their peak, and the mud only getting more sticky and unridable, they were quite a challenge. No wind, no shade, the corn sweat in full effect, we were now in an inferno. The mosquitos were out for blood, too.
There was one more aid station 17 miles from the finish to re-up on fluids but from there on in it was all about managing HR and cooling. More volunteers were at the finish line to wrap cold soaked towels around the riders necks. I collapsed onto the grass, rinsed the sticky gel residue from my hands, watched the race helicopter land, and drank two more bottles of water. The six hour drive home included stops for an Impossible Whopper and McD fries.
