Unveiled: Zipp Vuka Stealth
Integrated adjustability is the hallmark of Zipp’s new one-piece aerobar.
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Integrated adjustability is the hallmark of Zipp’s new one-piece aerobar.
Combining fit adjustability with aerodynamic performance is the mantra practically all triathlon gear companies are following today. The importance of both rider position and the drag created by equipment are practically universally agreed upon, but blending those two attributes is a tricky puzzle to solve. Zipp’s Vuka Stealth is their next solution to this equation. It integrates the stem and base bar while creating a broad spectrum of adjustment at the elbow pad and extension positions.
In order for a tri bike to fit many riders and different frames, it has to have a broad range of fit adjustment. Triathlete conducted a wind tunnel test (that will appear in the April issue) of four different high-end aerobars with widely ranging differences in adjustability—the test had a clear conclusion. Bars with minimal hardware might be marginally aerodynamically superior, but the differences are tiny enough that fit adaptability is far more important. Vuka Stealth has minimalistic hardware and a Kammtail-style base bar design to cut down on drag, but functionality and fit are this bar’s key attributes.
Stack and reach dimensions of the elbow pads and extensions are essentially infinitely adjustable. The stack position can be elevated high above the base bar using as much as 50mm of risers to prop the elbow pads and extensions in unison, maintaining forearm angle while changing only height. (10mm and 25mm options are available to reach intermediate positions.) The extensions and pad mounts can slide fore-and-aft without restriction, creating unlimited adjustment to the reach dimension.
The ability to manipulate stack and reach for both the elbow pads and extensions is the most important attribute of any aerobar, and Vuka Stealth offers all of the adjustment a fitter could desire to those dimensions. The compromise of its integrated design comes in the form of reduced adjustment to the less important, but still relevant, fit dimensions.
The biggest and most obvious functional differences between the two-piece Vuka Alumina and Vuka Bull setup and the integrated Stealth is the stem. Zipp’s outstanding modular system uses a standard stem, while the new version has the stem co-molded with the base bar. Once you pick a bar, your stem length is nearly fixed. A 10mm spacer can be added between the bar and the steerer tube to lengthen the reach dimension. Adjustments at the pads and extensions can accommodate aero position changes, but this stem spacer is the only way to lengthen brake grip location.
Extension width can only be positioned in two settings, with either 104mm from bar to bar or 140mm. They can also be rotated to create an effectively narrower hand position.
Elevating the hands to block the opening between the upper arms has been shown by multiple wind tunnel tests to save drag for many riders. Vuka Stealth can slope the extensions 6 degrees upward, enough to prop the hands up moderately, but not as high as some riders have pushed this trend. If you’re one of the few who wants to ride with your hands at eye level, this bar probably isn’t going to work.
Zipp is creating versions with three different stem lengths—small, medium and large—and intentionally avoiding effective length approximations. They claim “60-80%” of riders are expected to fit size medium, based on fit data Zipp has observed. All versions have flat stems with zero rise.
Zipp created an app called Vuka Fit to help riders find the best match without mounting a bar to a bike. Plug in the stack and reach dimensions of your frame and to your elbow pads and its trig calculator will spit out the bar that best matches your dimensions. This app also does the same for the two-piece Vuka Alumina clip-on bar.
Perhaps the most innovative and impressive feature of the Vuka Stealth is its internal cable routing. Integrated bars have long haunted mechanics because most force the unfortunate wrench to blindly fish a cable through a kinked and cluttered pathway. Any home or pro tri mechanic knows this pain. Zipp’s solution to this problem is brilliantly effective.
Since uniformity to triathlon brakes has long since passed, Zipp built two different exit points for the brake housing, one beneath the stem and the other behind the base bar wing. To route the housing through the port under the stem, the housing enters the opening first, passes between the bolts securing the extensions and pops out the brake grip without any fishing.
Feeding the cable through the rear openings is just as easy. Start by passing the housing though the brake grip instead of the exit point and it slides along the back of the bar and pops straight out the tiny opening without any coaxing. This subtle improvement over just about every other aerobar helps ensure smooth brake caliper function by eliminating dramatic kinks in the housing and makes maintaining a bike easier, since swapping cables and housing is less of a chore.
Zipp’s engineers were coy about how they were able to simplify the routing, but alluded to construction techniques that create a smooth and unobstructed path through the inside of the bar. It doesn’t have any hoses to guide the housing. I’ll venture a guess to how they achieved this feat. Many carbon parts are molded with the assistance of an internal bladder that inflates to create pressure against the steel mold when the bar is being made. The bladder is often left inside the part and becomes a source of routing difficulty. Vuka Stealth is hollow. Smoothness of the inner layer of carbon is another factor. Many parts have rough surfaces that prevent cables from sliding, but Vuka Stealth appears to be smooth and may have shaped channels inside the bar to guide the housing. Whatever the real reason for such easy cable movement, this design element is fantastically effective.
In addition to Vuka Stealth’s fit range, it has a few features borrowed from the two-piece bar that help maximize comfort and control. The subtly upturned brake grips have a bulb on the underside that fits nicely in the hand. It helps create a solid and comfortable hold on the bike when out of the aero position.
In the bars, the long elbow pads cradle the forearm and help prevent the rear from digging in to the arm.
Zipp added two bolt bosses beneath the base bar between the extensions to mount accessories. A Garmin mount comes with the bar.
Five or so years ago, integrated aerobars started loosing favor. The general level of fit knowledge and awareness had risen substantially and triathletes finally began eschewing streamlined designs that limited fit in favor of flexible ones. Maintaining position flexibility while integrating the stem is the primary focus of the Vuka Stealth, yet Zipp already has an exceptionally adjustable aerobar in their two-piece setup, so that begs the question, why build this bar?
The draw of integrated aerobars remains the same—they can be slightly stiffer, slightly lighter and slightly more aerodynamic than their modular counterparts. And they look fantastic. Zipp’s CFD (software that calculates aero drag) analysis showed this bar to be the aerodynamic equal of the old VukaAero, which offered far less fit adjustability. They did not compare it to their current two-piece system.
On the off-chance that the Vuka Stealth’s minor fit limitations impede your position, the benefits of going integrated would not be worth the sacrifice. But Zipp has done a fantastic job limiting the potential pitfalls, so Vuka Stealth offers the upside while still matching just about any fit. The price is typical for the high-end company from Indiana—it retails for $1200 with Zipp’s open-ended extensions.
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