By Lennard Zinn
Mavic’s TraComp carbon-spoke system, in which the spoke works in both traction and compression, has had a somewhat rocky beginning. A recall this year of all R-Sys front wheels was a black eye for Mavic, a company that has always prided itself on the reliability of its wheels.
But the problems led Mavic to a new understanding of forces on a wheel, particularly in crashes, and led to a new testing program for its wheels to reveal problems like that. And rather than give up on the TraComp idea because of the recall, Mavic has instead strengthened its belief in the concept and has come out with not only improved R-Sys wheels with aluminum rims, but a new, incredibly light R-Sys Ultimate wheelset incorporating the TraComp spoke system along with carbon rims and hubs.
Why the R-Sys Recall?
As many of you may have already seen in some rather alarming photos and YouTube videos out on the Internet, the original-design R-Sys front wheels of some riders completely collapsed when most or all of the spokes snapped off at the spoke nipples, separating the rim completely from the hub.
Generally, this was due to side impact, like a pedal or rear derailleur going into a front wheel. While the spokes were strong in tension and compression, they were weak against such an impact.
The rear wheel was never recalled, because even though the TraComp spokes in them are the same, only one side of the wheel has them, and the other side has aluminum Zicral spokes, same as on a Ksyrium SL.
According to Mavic, the aluminum spokes would prevent a pedal, for instance, from going beyond snapping off a single spoke, because it would hit an aluminum one, where it would stop. And even if somehow something got into the carbon spokes and snapped them all off, the aluminum spokes would still keep the wheel from collapsing.
The recalled front wheels and all-new R-Sys wheels, front and rear, now have a hollow carbon spoke that, rather than being made of only unidirectional carbon fibers around a hollow core, now has five layers of unidirectional fibers surrounded by two carbon layers spiral-wrapped around them, one wrapped clockwise at 22 degrees, and the other wrapped counterclockwise at 22 degrees (also around a hollow core).
The spoke is the same weight as before and, like before, stands straight like a chopstick if you push down on it when it is free standing (unlike a steel or aluminum spoke, which will bend). But now, if impacted from the side, it won’t snap, either. The spiral-wrapped spokes can be distinguished from their predecessors by two gold bands around them.
The R-Sys TraComp principle
Due to the fact that the TraComp spoke works in both tension and compression (an aluminum band under the heads keeps them from pushing down into the hub on compression), the wheels will not suddenly become flexy when they are stressed from the side. Instead, the spokes on the opposite side from the applied force now work like spokes in a wagon wheel and stand the rim up. This means that the spokes can be run at lower tension, and the rim is less stressed, leading to longer fatigue life.
Taking TraComp to the Max
The R-Sys Ultimate wheel, the wheel on which Ivan Basso recently won the demanding Giro del Trentino in the Italian Dolomite Alps, is a logical but still astounding progression of the TraComp technology. The wheelset is only 950 grams per pair — 410 grams for the front (that’s lighter than a light aluminum clincher rim alone!) and 540 grams for the rear with a titanium freehub body. It is designed for aggressive climbing — for attacking hard out of the saddle without giving away energy, tracking ability or rider confidence in side flex, while being feather-light and easy to carry up the mountains.
The 22mmm-deep carbon tubular rim weighs only 230 grams (advertised weight is 250 grams), yet the wheels are just as stiff as the R-Sys and R-Sys Premium wheels. Both sides of both wheels are laced with the hollow, spiral-wrapped carbon spokes; there are no Zicral spokes in the rear wheel. The hubs are carbon with carbon flanges.
Of particular note is that the spokes have zero tension when the wheel is not under stress. Thus, if you break a spoke, the wheel does not wobble in the least; it stays completely straight.
I rode a pair of these wheels on a long ride with lots of climbing this week in the “Pre-Alps” of the Dolomites, including up the 10km climb of the Passo Crosetta. They are incredibly light in the hand, yet they feel just as stiff as the stiffest of climbing wheels when riding. Going hard out of the saddle, they feel completely rigid, and at my weight and with the leverage of a tall bike and long cranks, climbing wheels often give that stiff, stiff, then suddenly completely spongy feel when thrashing them out of the saddle.
Descending, they track great and brake great, given the right brake pads. I used yellow Swisstop pads on the front and standard SRAM black pads on the rear to see how the wheels performed with both, without risking my neck by having grabby black pads meant for aluminum rims on the front.
The rear brake howled and grabbed, yes, but the front brake with the yellow pads modulated perfectly and silently — it felt just like an aluminum rim under hard braking.
The R-Sys Ultimate wheels are made in tubular only and are currently not available for purchase. Mavic made them for its teams and has not yet decided whether it will ever offer them for sale. If it does, it certainly won’t be in 2010. With zero spoke tension, the tolerance on the roundness and flatness of the rims has to be extremely high, or the wheel will obviously wobble or hop. And it is difficult to industrialize a process to consistently deliver that kind of stringent quality.
The R-Sys Ultimate was first raced in the 2008 Giro d’Italia. In this year’s Giro, the wheels will be used by three teams, including Basso’s Liquigas formation. The wheels used by cycling journalists at Cannondale’s 2010 SuperSix press launch will be passed on to the teams on Saturday, since only 10 pairs or so currently exist. Let’s hope that they go faster for Basso than they did for me, since I got dropped on the climb of the Passo Crosetta despite their low weight and great performance! Age, cunning, and great equipment still can’t trump youth and strength sometimes.