24 May 2018


If you’re a cyclist looking to compete and not just complete, or simply curious about your maximum achievable speed at your current fitness level or power output, there should be one, five syllable word on your lips; aerodynamics.


Maximising your ability to slice through air atop your bike is a critical factor in the science of getting ahead, and Vision’s range of cutting-edge Metron wheels deliver.


Shape shifter

Vision’s range are not only nice to look at, they’re arguably the most aerodynamic wheels on the market, due in part to their airfoil shape. If you have a round shape, as you might on a traditional road bike’s tubing, you have what’s called a bluff body, preventing speed because airflow can’t stay streamlined and attached. Instead, the flow just flies around the front to the maximum width, before separating and creating a lot of pressure behind the rider. With an airfoil shape – as seen on the Metron wheels including 40 SL, 55 SL and 81 SL, the airflow remains attached for longer and is smoothed out, meaning less pressure build-up behind the wheel so drag is reduced.


Winning on width

The Metrons are also 25.5mm wide, which is important because 25mm tires are reported to be the fastest around. Historically, thinner was thought to be faster, but recent research has shown that the 25mm tire can save about three watts at 40km/hr. It’s also proven that perfect aerodynamic performance requires a tire diameter ever-so slightly smaller than the rim width. Why? Because a tire diameter smaller than rim width allows the separated air from the tire to reattach to the rim surface, resulting in less pressure build-up and less drag. A tire with a larger diameter than the rim can create a situation where the air does not reattach, thereby negating the benefit of a deep-section rim.


Go with the flow

Finally, those deep rims ‘sail’ on crosswinds by making the airflow follow the shape of the wheel as it passes over at an angle, creating appreciated forward thrust. In principle, that’s why the Metron 81 SLs are faster than the Metron 55 SLs, which are, in turn, faster than the Metron 40 SLs. But choose your weapon; 40mm rims provide better handling than wider rims in heavy cross-winds and will be slightly lighter. In short, if you’re buying for something like a time-trial over a flat course, the 81 SLs can’t be beaten, but throw in a few hills over a technical mass sportive event and you might prefer the 40 SLs.


There’s also versatility within the range: Metron 40 SL, Metron 55 SL and Metron 81 SL are available in clincher, tubular and even disc-brake-ready formats. The merits of each deserve their own feature but, in short, clinchers are arguably the most practical as you can easily replace a puncture mid-ride; tubulars are known to be fastest thanks to the higher air pressure they can handle alongside the reduced material required; and disc-ready wheels provide the most stopping power because of the purported greater braking power and better modulation of disc brakes.

In short, the 2018 incarnation of the Metron wheels are Vision’s fastest yet. But, of course, there’s only one way (or two!) you can prove it to yourself…