Tuesday, July 16, 2013

The Importance of Tire Pressure

By James Schaefer, PCG Elite Coach

It’s race day, and I wake up to rain. The Weather Channel confirms my fears: the rain is headed right toward today’s race. I immediately envision the race course and its really fast, tight turns, and my thoughts turn to tire pressure. If it doesn’t stop raining, what pressure should I race with?

The answer to that question may be one of the most critical choices I make today. A few weeks ago I conducted a very informal survey of riders in my area, mainly in retrospect to my rear wheel skipping on me going through a turn in a race on a dry road. Several crashes occurred in that same turn during the course of the race. What I found in my survey was that the tire pressure choices our local riders make are as diverse as the riders themselves; they ranged from filling the tires to maximum pressure (no matter the conditions) to a philosophical discussion on rubber compound, temperature, and road conditions. 

What is the correct tire pressure you should run? When I started to race back in the days of hairnets, chrome box rims, and handmade silk cast tubular tires, I just cranked the tires up to what was on the sidewall of the tire. To me, the novice, this made perfect sense. High pressure equaled lower rolling resistance, and that was fast! This idea was reinforced when Continental started introducing tires you could inflate to 120 psi. We figured we could exceed the maximum by as much as 20%, so we were cruising around on 21-pound steel bikes with 140 psi in the tires and not a care in the world.

It wasn’t at all efficient, however, and doesn’t provide the grip needed to go around corners at top speeds. According to James Stanfill with Specialized Bikes, about the only place suited for maximum tire pressure is a wooden Velodrome. He makes sure that the tires of each rider he supports are properly inflated before each event. This is dictated by tire type, rider weight, and weather.

Lots of miles, road rash, and current research later, those old beliefs and practices have most definitely changed. If you do a quick search on the web about tire pressure, you’ll find many references to wider tires with lower pressure, especially during those cobbled spring classics in Northern Europe. For example, in Paris–Roubaix tire pressure can be as low as 60 psi.

But these are extreme conditions. What is the correct tire pressure for you? Your weight, the road conditions, and your tire type should all factor into your choice of tire pressure. Some of the tire manufacturers have recommended tire pressures on their websites, such as Michelin’s chart pictured below.

Don’t want to carry a chart around? Yes, there is an app for tire pressure. If you have a smartphone, check out Vittoria’s app. For my weight and riding style, it’s right on. 

So the next time you’re about to roll out of the house or line up at the start line, take a moment to consider your tire pressure. You just may be able to carve that tight last turn and have a podium finish in your future.