Tech Details
Stork 69ers use Zipp’s patented ABLC (Advanced Boundary Layer Control) dimple technology to create a slippery “boundary layer” of air alongside the rim’s surface to reduce drag, netting speed increases. Wind tunnel testing of ABLC rims reveal a 3% drop in drag over a smooth surfaced carbon wheel of the same profile. Zipp applies hundreds of dimples on a hybrid toroidal rim shape (incorporating 5 wind tunnel tuned compound curve profiles), adding a low-drag/max-durability optimized spoke count with a 21-22 mm frontal section, producing a low drag wheel that’s tough enough for road racing, yet aerodynamic for time trialing.

Constructed with unidirectional pre-preg carbon sheeting, the 69er rim has a Micro-Porous Silica Ceramic Matrix braking track that is slightly rougher, with a strengthened spoke nipple bed. A bundle of Kevlar threads is laminated at the leading outer edges of the rim to distribute compaction forces and impacts across the rim’s diameter, much like a key-stone cap in an arch. To further reduce vibration from rough pavement surfaces, a supple visco-elastic material is sandwiched in the rigid carbon laminate.

At Interbike 2008, Zipp’s Andy Paskin showed me one of their full size, resin based SLA (Stereo Lithographic Apparatus) prototypes used in wind tunnel tests. With SLA output, Zipp creates an accurate prototype for rim shape, with full compound curves and depth, which can be tweaked in the tunnel to yield optimal results. Gotta love when aviation manufacturing technology filters down to a bike wheel!

In a tip of the hat to practicality, Zipp uses traditional aluminum nipples that are readily accessible, right at the rim, for any out-of-true touch ups. To firmly crank down the included valve stem extension, the tube is broached with a 3mm Allen key fitting. Zipp recommends using a little Teflon tape to totally seal the stem. Bearing adjustment is straightforward, requiring a pair of 5mm Allen keys. Ideally you should also use a torque wrench to set final preload.

To connect hub and rim, front wheel lacing is radial, and the rear is radial non-drive and 2X drive side. As supplied by Storck, the wheels came pre-glued with low-rolling resistance Schawlbe Stelvio tubulars in 22mm. And because the 69ers were supplied with tires glued, I didn’t confirm the weight listed on Storck’s website. However, I did weigh each wheel with tire and w/o skewers, yielding a total package of 1890 respectable grams (rear: 1010 grams, front: 880 grams).

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