3-12-07 // Online Exclusive: Mavic Tech Days 2007

Mountain bikes have changed a lot over the past 20 years, but no matter how much travel you add or how light your frame and components become, your bike is always going to have two wheels. One of the most well-known wheel brands is Mavic. In the early ’90s, Mavic’s venerable 231 rims helped the French road-cycling company expand into the world of mountain bikes. Mavic’s early mountain-bike rims were much different from today’s pre-built Mavic Crossmax wheels, but the same basic engineering principles apply. Last week I traveled to Mavic headquarters in Annecy, France, to learn about some of those principles and see firsthand what goes into making some of the fastest wheels on the planet.

Unlike most press junkets, the purpose of this trip was not a specific product release or even a factory tour. My sole mission was to learn about the science and testing that goes into designing Mavic wheels. The criteria for wheel performance include weight, inertia, stiffness, aerodynamics, reliability/durability and efficiency, but for two days we focused simply on stiffness. The topic was expertly discussed by Olivier Mouzin, Mavic’s advanced research engineer.

Mavic's new Crossmax SX wheel uses a wider rim and wider spaced hub flanges in concert with rigid alloy straight-pull spokes for increased lateral and frontal stiffness.

Wheel stiffness can be divided into three categories: frontal, lateral and torsional. Frontal stiffness is wheel distortion from a radial load, such as the force applied by the weight of a rider in an upright position. This distortion is negligible and impossible for a rider to detect since it’s masked by tire deformation. Lateral stiffness is distortion experienced due to a side load. It’s difficult to perceive while riding, but it can prevent a cyclist from achieving full power when sprinting out of the saddle. Torsional stiffness is distortion under hub torque and only affects the rear wheel.

One factor in wheel stiffness is the dimension of the rim. The rim’s height affects its frontal stiffness more, and the width has a greater affect on lateral stiffness. A rim’s diameter is also important—as it decreases, both the rim’s lateral and frontal stiffness increase. This is obvious when comparing 29-inch and 26-inch wheels. Although these dimensions should not be overlooked, the rim stiffness is just one small factor in the overall stiffness of the wheel.

Hub geometry is important too; larger flanges increase frontal and lateral stiffness slightly, but increasing the flange diameter can also add weight. Another important thing to keep in mind: The stiffer the axle, the stiffer the wheel, both frontally and laterally.

With this device Olivier applies a lateral load to a wheel held in a very stiff frame. Then he measures deflection at the point the force is applied as well as a point on the rim 180 degrees from the load.

You can’t talk about wheels without discussing spokes, and much of Mavic’s discourse revolved around spoke theories. For instance, reducing the length of the spokes can make a wheel stiffer, but doing so also affects weight and inertia. Many Mavic wheels use alloy spokes with a large cross-section for greater stiffness. The shape of the spokes doesn’t affect wheel stiffness, as long as the cross-section of spokes has the same area. Straight-pull spokes are 16 percent stiffer than conventional spokes with an elbow, and if those same straight-pull spokes are made from double-butted wire, that stiffness increase is reduced to 12 percent. Not surprisingly, fewer spokes equates to lower wheel stiffness.

Reader Comments 

Posted Mon Jun16, 2008, 2:35 PM — By Yadira

HI! I' don't write and speak english very well, but I try. ok? I have a Mavic wheels, but one spoke is broken and I' like replace, can you tell me where I can buy o get them or wath can I do? Please answerme its very important. I wait your e-mail

Posted Mon Nov 3, 2008, 9:13 PM — By toure

lifetimemoviedownloads.com This is #1 Movie Downloads Site. Unlimited Access Over 80 Million Full-Length DVD Quality Movies, Music, Tv Shows, Anime, PC Games and much more

Posted Thu Jun18, 2009, 3:32 AM — By susan

replica handbags replica bags 2009 designer Handbags

Posted Fri Jun19, 2009, 4:46 AM — By  jewelry

jewelry jewelry wholesale

Posted Sat Jun20, 2009, 3:26 AM — By links of london

links of london charms links of london sweetie bracelet links of london bracelet

Add Comment

Name (Required):

Email (Required, will not be shown to public):

Comment (Required, max chars: 1024):

You have characters left.

Type the characters you see in this picture