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Mavic is at it once again. They rocked the wheel world with the introduction of the Helium. They did it with the Cosmic. Then they did it again with the Ksyrium. Since the Ksyrium seems to have been taken about as far as it can go, Mavic is introducing the R-Sys. A quick glance proves that something is different about these wheels, and it takes stopping a R-Sys-shod bike to see what's going on. It's the spokes. They're hollow, tubular carbon fiber, not really spokes at all. More like rods. And their beauty is that they work in both tension and compression. By contrast, conventional wire spokes work only in tension.

Spokes: Tensioned spokes are what make bike wheels so fascinating. Most spokes, when taken out of a wheel, are flimsy wire gauge that bend easily. Tension up that same flimsy wire and it can be an integral component in an object that can withstand tremendous force. The key to the spokes working is that they are tensioned in harmony with a mess of other spokes; due to vertical or lateral forces a single spoke can lose tension for a moment, but the other spokes in the wheel will counteract with greater tension. Too little tension in a spoke and the wheel won't stay true; too much tension and the wheel will destroy itself. The fewer the spokes in a wheel, the more load each spoke has to take, making tensioning the spokes an ever-finer balance. Rims and hubs also play into this spoke tension equation. Spoke flanges that don't have enough material on the outside of the spoke hole can fail as a result of too much tension (witness Shimano's hub warranty, which excludes radially-laced wheels). And a rim can fail from too much tension as well.

Mavic has been playing with spokes for a long time. The Ksyrium has Zicral aluminum spokes instead of traditional stainless steel spokes. The Zicral spoke, combined with the matching nipple are lighter than a steel spoke and brass nipple, 7g compared to 8g. Their new carbon fiber spokes, with nipple, are 5g. And these carbon fiber spokes have an aluminum head bonded to one end and aluminum threads bonded to the other. They call this "Tracomp," meaning the spokes work in both compression and traction.

Mavic has also been playing with rim weights for a long time. In a bygone era, they made 280g aluminum rims, but they were tubulars made with the idea that no fewer than 28 spokes (24 if the rider was super light and smooth) would support the rim. As they went to low spoke count wheels, the rim weight went up and the cross sections went deeper. The R-Sys is a new direction for Mavic, with a sub 400g clincher rim and a shallow rim profile. Take a look around the bike market; there are very few sub 400g clincher rims out there, and the few that are sold generally need lots of spokes to stay true.

Mavic has been a hub manufacturer for a long time and has experimented with different hub flanges. When they went to a cassette hub, they narrowed the distance between flanges and increased their diameter. When they developed the Helium, they worked out a minimal flange pattern and employed straight-pull spokes. And with the Ksyrium, they evolved ever leaner hub bodies.

With the R-Sys, since the carbon fiber spokes don't need as much tension to stay in place, and barely compress at all, the rims the spokes are attached to can be lighter than other clincher rims, and still be plenty strong. And the new hub body is about as minimal as a hub can get. The flanges supporting the carbon fiber spokes can be thinner than with Zicral spokes because the spokes don't need as much tension.

Put the rim, spokes, and hub together, and tension the spokes, the result is a tremendously strong wheel. Vertical stiffness with wheels is pretty much a given, but this wheel has incredible lateral stiffness as well. 56 Nm of lateral force before either the front or rear wheels start to laterally deflect, which makes them 30% stiffer than the Ksyrium ES. This stiffness makes this a great wheel for crit riders and big riders. Put a wheel into extreme situations, and the sideways flex that vexes some riders, leading to overworked and eventually broken spokes on some wheels; this will just about totally disappear.

The stiffer spokes should also lead to greater efficiency. The less the spokes stretch, or absorb energy from the hub, the more energy will be put into the rim propelling the tire on the ground. This is a great thing for all riders.

One thing that might surprise people is that the rear drive side spokes are Zicral, not carbon fiber. Using tubular carbon fiber spokes would have created a wheel with unacceptable dish. Another rear wheel surprise is that Mavic uses an asymmetric rim; the spoke holes are off-center. A number of companies already do this, but it's a first for Big Yellow. They, like the other companies, do it to better balance the tension between the drive and non-drive spokes.

Like all Mavic wheels, this set is easy to work on. Two five mm Allen Keys will take apart both hubs. The bearings are easy to tap out and in, and the freehub mechanism is their established light weight cassette body and pawls. While spokes can be trued at home, one needs to open the hub and remove the Tracomp ring inside the hub before the spokes will move.

The Mavic R-Sys wheelset has 16 front spokes and 20 rear spokes. The rims are made of Maxtal aluminum alloy and are milled between the spokes for weight reduction. The front rim is 22mm tall for both the clincher and tubular versions; the rear is 25mm tall for the clincher version and 22mm tall for the tubular. The front wheel and the non-drive side of the rear have 4mm thick tubular unidirectional carbon fiber spokes. The rear drive side spokes are Zicral aluminum, straight-pull, and set up in a two-cross pattern. The front and rear hubs are both made from one piece of aluminum alloy. They run on Mavic's QRM+ bearings and have an aluminum axle. The rear wheel has Mavic's FTS-L freewheel mechanism. The front wheel has a speedometer magnet built onto a spoke that can be slid up and down. Mavic's BR601 skewers are included with the wheels, as are Mavic wheel bags. The wheels come with a spoke wrench (similar to the Ksyrium, but a larger diameter nipple) and a ring removal/installation tool. The MP3 two-year extended warranty can be purchased with this wheel. The clincher wheelset weighs 570g front, 785g rear. The tubular wheelset weigh 570g front, 760g rear.