Friday, 25 December 2015

Tire Pressure - Cold Temperature Effects on Fat Bike Tire Pressure

Being new to the fat bike game, there have been a number of little surprises.  The first surprise was how easily the bikes roll and the second was how low the tire pressure is on a nearly 5” wide tire.  I am used to 110 psi on my road bike and 20 – 30 on my mountain bike.  Fat bikes tires need pressures hovering around 10 psi or less (I will cover my experience with various pressures in another installment)

Another revelation has been how temperature affects tire pressure as I had never ridden a bike in sub zero temperatures…  On my first ride, I felt the tires were getting softer shortly into the ride.  Sort of felt like I was getting a flat!  After checking in with a few folks who were “winter riders”, I learned that due to the low pressures, even a drop of a 1 or 2 psi would result in a significant change in the handling.

I needed to conduct my own experiment….  I filled a tire to 9 psi, set it outside at minus 15 degrees Celsius and measured the pressure after two hours.  The pressure went down to 6.75 psi, a drop of 25%.  Good to know!

I found a Botranger chart that can be used as a rough guide for various temperatures.  I say “guide” as my experiment showed less of a loss than the chart.  Tire volume is a variable.

My lesson learned?  Fill up at home, expect a couple psi drop and plan to adjust on the trail depending on temperature and conditions.






1 comment:

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