White Mountain Wheels
Design vs Marketing

Marketers have a need to differentiate their products so they can claim improvements and charge higher prices. Unfortunately "reinventing the wheel" results in inferior performance more often than not. Following are a few examples of recent wheels that were designed to be different, but were all bling and flash rather than substance.

Mavic R-SYS

I'll give Mavic some credit for really thinking outside the box on these. By utilizing fairly large carbon tubes for spokes, they were able to make a wheelset where the spokes not only can be loaded in tension, but will also take significant compression loads as well. This allowed them to use a large NDS offset on the rear wheel (resulting in good stiffness) without worrying about those lightly-tensioned spokes going slack.

But... large round tubes have very poor aerodynamics. They marketed them as "climbing wheels", but there are few races or rides where you spend all of your time going uphill at slow speeds. Also, at 1380g they were not what I would call exceptionally light... my personal clincher wheels with Alchemy hubs, Kinlin XR200 rims, and CX-Rays spokes are more than 100g lighter, and much less expensive.

Unfortunately this wasn't the worst of it. Not long after they became available, a photographer captured a high-speed photo sequence at the end of an amateur race. In them you could see a rider in the sprint appear to touch the rear derailleur of the rider next to him with his front wheel. In the next photo there was a flying piece of carbon spoke evident, but the wheel appeared intact... but in subsequent frames all of the spokes snapped in rapid succession. With nothing left to hold up the front of his bike, the rider landed hard head-first and took out another rider as well.

This sort of thing has since happened to a significant fraction of riders on these wheels. Mavic's response tends to be that external damage is the cause of these accidents, and in some cases they are correct. Still, a conventional wheel does not self-destruct when one spoke breaks. Usually the worst that happens is a bad wobble that must be fixed before you can continue. I suspect that the inherent lack of ductility in the carbon spokes and the fact that they are constrained at both ends makes them a poor choice. The loss of one spoke creates enough instability that other spokes become stressed beyond their yield point and snap. In my opinion cycling is hazardous enough without using wheels that might suddenly explode.

Google R-Sys failure for some interesting reading.

Time Hi-Tense

The major "innovation" here is a rear wheel with a NDS (non drive side) hub flange offset that is so small that the spoke tension on both sides of the wheel is nearly the same. I guess this appeals to people who are unduly disturbed by the utter lack of symmetry in most rear wheels. But that asymmetry is there for a very good reason... to provide lateral stability and stiffness to the wheel. The lateral stiffness imparted by the spokes increases with the *square* of the bracing angle (ie exponentially), so this bracing must come from somewhere. With wide cassettes and a 130mm dropout spacing we are stuck with only 16-19mm of offset on the DS, so to obtain good wheel stiffness most manufacturers have settled on 34-39mm of NDS offset as the optimum, yielding a tension on the NDS of slightly less than 50% of the DS. So long as the more lightly tensioned NDS spokes do not go slack in use, it performs very well.

By making the NDS spacing only a little bit greater than the DS, Time started with an inherently unstiff design. To compensate for this, they opted to use a heavy rim and spokes. This is really all they could do to obtain decent stiffness. The name of the wheelset implies that some "improvement" was obtained via high spoke tension, but this actually has no positive effect on the stiffness at all. So they've ended up with an aluminum rimmed wheelset that weighs 1550g (a weight I normally beat when spec'ing $700 wheels for 250lb riders), costs $1500 (!) and is almost as strong and stiff as wheels that cost half as much and weigh a lot less...

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. By making the NDS flange spacing very large they can cut the number of spokes on that side in half and still obtain both good stiffness and relatively high NDS spoke tension.

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 achieve 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 26-30mm rim with aero SS spokes, as there is between that wheel and one with a 50mm carbon rim!