June 24, 2011 at 9:45 pm #93212Keymaster
ENVE’s latest rim design, the Smart 6.7, is the result of extensive collaboration with UK-based aerodynamics specialist Simon Smart. Articles such as those from ProCycling and VeloNews have detailed much of the innovations utilized in production of the 6.7 rims. In reading about the 6.7 rims and viewing several photographs, I had made some basic assumptions (mainly that they closely resemble rims from another manufacturer). I was excited to be able to get a close look at the Smart System rims so that I could see for myself the details in this new design.
Firstly, these rims look slick. ENVE’s typical stealthy unidirectional carbon look has been enhanced by jet black, die cut decals for that “murdered out” look that seems to be growing in popularity within the cycling industry. Aesthetically, the brake track on the 6.7 rims has been greatly improved over the previous generation rims. One of the main improvements for this new generation of rims is in the brake track. In order to avoid compromising the aerodynamic rim shapes developed in the wind tunnel, ENVE had to go back to the drawing board to create a seamless transition between the rim surface and brake track. Using an entirely new production method, a textured brake track is molded directly into the rim, with some minor sanding finish work to improve the consistency of this texture. The result is braking response that is closer to that of an aluminum rim with less of the heat buildup that can cause warping and failure in carbon rims.
An interesting discovery made by Enve and Simon Smart dispels the myth that higher spoke counts yield greater aerodynamic drag. This knowledge allows ENVE to stick with the traditional “low” spoke count of 20 front and 24 rear. This keeps hub options open and helps to lower production costs. Since ENVE’s spoke holes are individually molded for greater strength, each separate spoke count would require its own expensive rim mold.
To get a basic idea of the aerodynamic structure of the 6.7 rims, think WIDE. Simply put, the leading edge of each rim’s inner diameter closely matches the tire profile on the outer leading edge. At the tubular tire bed, the front rim is 26 mm wide, while the rear is 24 mm. The rear rim has been designed narrower for aerodynamic reasons, but an added benefit is that some frames use wide chainstays that would prevent use of rims much wider than 24 mm. A secondary benefit of a wider profile on tubular rims is that there is a greater contact area between tire and rim for improved safety and rider confidence. In the design process, ENVE was obviously thinking about better tire adhesion, because they’ve also added in a channel that allows better fit for traditional tubular tires with thick seams.
After closely examining and handling the Smart System rims, I’ll say I’m impressed. While a lot of the hype surrounding these rims is based on their aerodynamic performance, ENVE has gone a step further to greatly improve their production methods to create an unbeatable combination of strength, stiffness, and low weight. In the coming year, we expect to see quite a lot of these wheels backing up the best riders in several cycling disciplines. And look forward to the release of additional Smart System rims; a shallower and lighter all-purpose set, and a deep section time trial specific set. Beyond that, ENVE is in constant development mode, improving upon existing designs and production methods to stay at the industry’s cutting edge.