The wattage differences claimed by various rolling resistance studies are so dramatic they are hard to ignore. Several tests claim that choosing the correct tire at your LBS can have as much as a 10, or even 20 watt resistance difference. Everyone with a power meter knows that a 10-watt boost is enough to push you down the road noticeably faster. The thought of giving up that much power simply by running the wrong tire is enough to send otherwise professionally behaving people into hysteria.

But the effect of rolling resistance has been blown out of proportion.

Roller drum tests are the most controlled and repeatable studies on rolling resistance conducted so far. Basically, they stick a tire against a metal drum, spin the drum at a pre-determined speed and measure how much power it takes. Simple enough. The only problem is that a perfectly smooth cylindrical metal drum has very little in common with a real life road.

When a tire rolls over a pebble in the road, the pebble creates an indentation into the tire and it also lifts the tire slightly off the asphault. Some tires are more supple than others, so they require less force to deform with the same pressure in the tire. The roller drum test creates a similar, but unrealistically large indentation into the tire. Because the indentation is so much larger than what a tire experiences on the road, the wattage differences measured by these tests are dramatically inflated. Despite this inaccuracy, the roller drum test is able to measure the relative rolling resistance of different tires. But no one has conducted a test that replicates a road well enough to measure the difference in watts.

These tests show that clinchers have much less rolling resistance than the exact same tire in tubular form. The ~10watt difference claimed by some of these tests has driven many people to consider clincher race wheels. The roller drum tests have shown that clinchers do in fact have less RR than tubulars, but they are not able to accurately quantify the difference. Still, these tests have made clincher race wheels a popular choice.

Several companies are producing worthy clincher TT wheels, and we will be reviewing them through out the summer. Check back in for a verdict on the Reynold SDV 66c, Flashpoint 80, HED Jet 60 C2, Zipp 900 disc, Blackwell Research Carbon Clincher 50 and the HED Jet Disc.

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Aaron Hersh is the Technical Liaison at Colorado Multisport in Boulder, Colorado. He has been competing in endurance sports for the last seven years. Hersh has a B.A. in Integrative Physiology from the University of Colorado, focusing on biomechanics.

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