Betcha didn’t even know there was a debate on this arcane topic, didja? It came up the other day when a club member, who is a pretty good rider and is usually out front on our group rides, said he’d switched to the slightly wider 25 mm tire. He said he was pleased at the better ride, better traction, better cornering — all at no appreciable increase in rolling resistance.
That touched off a firestorm on our club Yahoo board. Why, there must have been eight or nine comments bouncing back and forth about the relative merits of the 25s vs. the skinny 23s that most of us “macho” bikers ride.
And one member pointed out that the size of the contact patch (where the rubber meets the road) is more dependent upon the circumference of the rider’s waist than the width of the tire itself. The wider the waist, the greater the bulk, the higher the weight, the more tire deformation — they all add up to more traction, but with more rolling resistance.
Although, if you want to really gauge rolling resistance, the famous wheelbuilder Jobst Brandt has a nifty little interactive page that lets you calculate the rolling resistance of your tires after you enter the effective frontal area of the tire, its drag coefficient, the air density, the combined weight of the rider and bike, the phase of the moon, the odds of your maternal grandmother being born on a Sunday, and multiplying that by the slope of the regression line of the area of adhesion.
I haven’t tried 700 x 25 tires on my bike. It came with 23s, and I’ve been happy with them. But for a smoother ride, it might be worth the switch. Can you enlighten me any further on this burning topic?