Design vs Marketing

A few examples of wheel that were designed to be "different" at the expensive of performance, are the FSA RD-600, Campagnolo wheels with G3 lacing on the front, and any wheel that has aluminum spokes.

FSA RD-600

First, lets look at the FSA RD-600, touted by FSA as "The dawn of a new era in wheel design."

The most unique feature of these wheels is the very large center hub flange. It is certainly eye-catching, and no one would ever confuse these wheels with another. Only the center flange has angled spokes that take torsional loads; all of the spokes on edges of the hub are radially laced and only resist lateral loads. Conventional wheels accomplish both of these tasks at the same time by having spokes attached at the edges of the hubs, and crossing some or all of them to resist torsional loads. Having the spokes perform both jobs, with fewer flanges is more efficient. FSA claims "3 flange hub shelters 1/3 of spokes from wind". The center flange design does shelter some of the spokes from the wind at zero yaw, but at any greater angle, the flange will surely cause more obstruction than a conventional hub. What FSA has done simply adds extra weight (and/or reduces strength) while providing no benefits. The real mystery is why the *front* wheel also has a dedicated center flange and spokes to resist torsional loads, when the torsional loads on the front wheel are nil. The only answer is that they wanted the front and back wheels to both be unique and look the same. On the front wheel the center flange and it's spokes are *completely* wasted... there is no torque to resist and the center spokes provide zero lateral stability. On the back wheel it serves a function... but is less efficient than a conventional wheel.

Campy G3 lacing... on the front wheel

For several years now Campagnolo has been building wheels that use a "G3" lacing pattern (also called triplet lacing), where the spokes are arranged in groups of three, with one spoke from one flange meeting at the rim with two spokes from the opposite flange.

On the *rear* wheel this is actually a sensible design. I like to build wheels this way myself if I'm using a hub with a wide flange spacing and a stiff rim. Wide gear clusters have made it necessary to have a great amount of dish on the rear wheel, and this results in a large imbalance in the spoke tension. The issue with tension imbalance is that high lateral or radial loads can cause the low-tension spokes to go slack, which can lead to spoke fatigue and even wheel collapse. Campy's solution is to cut the number of spokes in half on the non-drive-side (which normally has the lowest tension), and space the flange on that side over a little bit. This results in even tension on both sides and (possibly) better wheel strength.

The problem is that they've also applied this same lacing pattern to the *front* of some of their wheels, where it makes absolutely no sense at all. Front wheels are not dished, and so the spoke tension is already balanced. By using G3 lacing on the front, they've created an *unbalanced* tension situation where one did not previously exist. The only possible reason for doing this is to make the front wheel look unique and similar to the rear wheel. To Campy's credit they only use G3 lacing on the front of their lower priced wheels, were it is a bit easier to trade design efficiency and weight for esthetics. On their higher priced wheels, they use a radial lacing pattern on the front.

Aluminum spokes

Mavic has been building wheels with aluminum spokes for several years now, and recently Campy (and their spinoff company, Fulcrum) has been using them as well. So is aluminum a better material for spokes? This is interesting, because I looked into making aluminum spokes 15 years ago and rejected the idea because there was no benefit. The stiffness to weight ratio and strength to weight ratios are no better than stainless steel, and the fatigue properties are worse. For hollow structures like a bicycle frame you can acheive a strength to weight and stiffness to weight benefit by using tubes with a larger diameter. The torsional and bending stiffness improves when you do this. But spokes are only loaded in tension, and aluminum in that application provides no benefits at all. In addition, because aluminum is a very light metal, the cross sectional area needs to be increased by a factor of 3 to get performance similar to steel. This increases the aerodynamic drag.

I didn't consider the marketing angle though. Those big color-anodized spokes made the Ksyriums look different than anything else... and it wasn't too difficult to convince customers that this difference was an improvement. It looks like Campy is following their lead. Of course they don't put these on their aero wheels and they never have, but I think it is sad that they are abandoning *all* aero considerations in their aluminum rimmed wheels. Aerodynamics is more important than weight in most conditions, and it matters even when you aren't doing a time trial. There is as much aero difference between a Ksyrium and a good 30mm rim with aero SS spokes, as there is between that wheel and one with a 50mm carbon rim. See: Aerodynamics