I love it when someone comes up with a simple way of illustrating a point. Rolling resistance in tires is real and it's a problem for trucks. But how do you quantify it? Percentages are vague. This little test is not vague at all.
If low-rolling-resistance tires make this much of a difference in this clever little demonstration, how much of a difference does it make with 18 wheels on the ground? Photo by Jim Park.
I recently spent an afternoon at Belle Tire in Allen Park, Mich.; a stop on Bridgestone's Ecopia Road Show tour now making its way around the country. Bridgestone says Ecopia tires are all about reducing rolling resistance, and they've come up with a cute and clever (a great combination in the marketing world) way of demonstrating rolling resistance. It's not really quantifiable, but it's pretty obvious. It may not be directly applicable to big trucks, but you'll get the point in a hurry.
The Ecopia concept originated in the passenger car world, so the car tires used in the test were identical passenger car tires, except the tires on one of the little four-wheel buggies pictured above were Ecopia, the tires on the other buggy were not. The tread patterns were identical, but the compounding was different.
The rider rode each of the carts to keep the 'payload' the same in each test.
The test was simple: ride each of the carts down an inclined plane, raised about eight inches, and stay aboard until rolling resistance brings the thing to a stop. When it stops, a Bridgestone guy runs out and places a cone where the front wheel stopped. The test was repeated with the second cart (with the low-rolling-resistance tires), and the distance between the two stop markers compared.
The green cone (naturally) in the photo shows where the low-rolling-resistance tires stopped. The silver cone shows where the other stopped.
Surprisingly, given the modest boost the carts got from gravity at the start, the cart with the low-rolling-resistance tires coasted about 10 to 12 feet farther than the other. Point proven.
Granted, the test could have been rigged by inflating one set of tires more than the other -- and I'd be none the wiser -- but I doubt it. They weren't trying to sell passenger car tires, merely illustrate the potential losses resulting from rolling resistance.
Several years ago, Michelin did a coast-down test
to illustrate their tires (at the time) had less rolling resistance than other leading brands. From 40 mph, the Michelin-equipped truck did coast farther in neutral than the others -- all other things being equal. My point in referencing the test is only to demonstrate that there are differences in the tires.
In the real world, the energy required to overcome tire rolling-resistance comes out of your fuel tank. As Bridgestone's cute little carts illustrate, there is a difference, and it's too big a difference to ignore. If you would like to make a comment on this blog but do not see the comments box below, please click here.