Thursday, June 2, 2011

What is the optimal tire pressure for cycling? Part 1

In autocross, knowing the correct tire pressure based on the terrain of the course can shave hundredths of a second. General rule of thumb is that when tire pressures are too high, it will produce too much sliding and pressures that are too low will reduce responsiveness and grip (in corners). In daily driving conditions, high pressures will not absorb shock very well and produce a rough ride; whereas, low pressures produces a smoother ride, but increases the amount of tire making contact with the road which leads to excessive friction and poor fuel economy. The perfect tire pressure for automobile tires is one that utilizes 100% of the contact patch on the corners and the straightaways.

On to the bicycle- because bicycle tires are extremely narrow, lack contact patch indicators and don't have to worry about spinning from hard acceleration, it's difficult to determine what the best tire pressure is. I found two sources to help me figure this out.

At the Michelin's website, they have a nice chart that shows tire pressure suggestions based on rider weight (load) and tire sizes 700x28/32C, 700x25c and 650x23C/ 700x20/23C tires. See the link to their chart below:

For a 145 pound rider like myself, the chart says that my tires should be around 103 psi. I thought this was a good suggestion EXCEPT that they didn't take weight distribution into consideration.  Because there's less weight on the front wheel, less tire will contact the ground which means less grip for turning. It seems more logical to use a lower pressure in the front and a higher pressure in the rear to account for weight distribution. Maybe 103 rear and 95ish front?  I'll have to keep looking..