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What happens to tire pressure during a race?

Lots of things happen during a 206 mile adventure like The Dirty Kanza that make it a must for anybody interested in two wheels. The preparation and execution require the perfect combination of emotional, physical and mechanical fortitude and the different approaches to this challenge are part of what makes the event so special. 

It’s no surprise one of the more debated topics is tire choice and tire pressure. Make the wrong choice here and the unforgiving Flint Hills will show no mercy. The challenge essentially comes down to finding the point where the tire can absorb as much of the rocky surface as possible, which translates to lower pressures but not so low that the rim is making contact with larger obstacles risking a pinch flat or damage to your rim. As tire pressures are reduced the margin for error decreases- at 40 psi just a few psi above or below can start to significantly impact tire performance. Add in variables like temperature, altitude and inaccurate pumps and gauges and you could easily be 10 psi off your target without knowing it.

To help illustrate this point we’ve taken a second-by-second look at one competitors TyreWiz pressure data for the entire 206 mile event. As you can see from the chart pressure started out at 40 psi (after a quick start line top-off from 37). Temperature at the start was about 80 degrees but actually decreased slightly to 75 over the first couple hours which resulted in a slight decrease in tire pressure to 39 psi. As the day quickly warmed up to 95 degrees you can see pressure increase to 41 psi by hour 5. The spikes you see up to 42 are after extended (5-10 minutes) stops for fuel etc. The bike was sitting in direct sunlight and the effect was immediate and significant but quickly stabilize once on the move again. Finally, as the day progressed it did cool off significantly in the final 3 hours back to 80 degrees with some assumed “leak-down” contributing to final tire pressure of 37 psi.

Nothing here is abnormal or responsible for any signaling a needed change in equipment or set-up but it is important to remember that there are a lot of factors impacting your ride and that quantifying these factors can lead to important insights as you reflect on your adventures and plan the next.

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