About a year ago, Zipp made a splashy debut with its 454 NSW carbon wheelset. Designed in the Indianapolis-based company’s advanced engineering lab, called the “Nest” (NSW stands for Nest Speed Weaponry), the 454 NSW had an undulating inner profile inspired by the shape of a whale’s fin, creating a rim that was a little more aero but, more importantly, a lot more stable in crosswinds than the 58mm-deep Zipp 404s.
As the benefits of this technology would presumably be more important with deeper-section rims, we expected Zipp to eventually apply the same innovations to the most aerodynamic wheels in its line: the 808 NSW.
And last week, a few days shy of the IRONMAN World Championships in Kailua-Kona, Hawaii, Zipp revealed its new 858 NSW wheelset.
Speed = Aerodynamics + Handling
Brakethrough Media
Like the 454s, the 858s incorporate Zipp’s undulating SawTooth rim profile. SawTooth was borne as the latest step in Zipp’s mission to make faster wheels by chasing not only maximum watts savings, but other attributes like better handling and braking performance. With SawTooth, Zipp engineers sought to optimise what they call “aerobalance,” or the balance of aero savings with handling stability along the entire yaw sweep (every potential wind angle).
SawTooth is an example of bio-mimicry, an innovation method that looks to nature to solve problems. Our initial post from the 454 NSW launch goes in-depth on the technology, so we’ll just do a quick primer here.
Zipp engineers took inspiration from humpback whales, which are surprisingly nimble – the animals, which are typically the size of a bus, move at 25mph and have a five-foot turning radius. Part of what makes this possible is a series of nodes on their fins, which cause regular disruptions in the water around them, making it easier to turn.
So how would similar shaping reduce side forces on a wheel? When you’re riding, air flows around the rim in various directions, forming vortexes that are not unlike eddies of water flowing around, say, a rock. These vortexes build until they are “shed” by the wheel. When this happens, it exerts a minute, lateral force on the wheel. This buffeting effect makes the wheel less stable – particularly when it starts getting hit by an external side force (crosswinds).
Check out the Zipp 404 wheels in this video from our American sister title Bicycling:
Designing the wheel with nodes on the inner diameter – Zipp calls them HyperFoils – forces these vortexes to shed at a higher frequency, thus exerting smaller and more regular forces. This means less input on the wheel and more stability in crosswinds. According to Zipp, the 858 NSW reduces steering torque (side forces that result in steering input a rider can feel) by a whopping 34 per cent, compared to the 808 NSW.
With the 858 NSW, which has a rim depth that ranges from 77mm to 82mm, the most common application will probably be time trial and triathlon. In this scenario, Zipp’s goal is to give the rider more handling stability so that he can stay in the low, tucked aero position more, instead of having to sit up to hold the bike on its line in high winds. According to Zipp, every extra minute an age group triathlete spends in the aero bars instead of on the bullhorns saves 8.6 seconds.
But Zipp says the 858 can also serve the performance-minded road rider, too, who may have shied away from deeper-section wheels in the past. “We say that it’s more aerodynamic than an 808, but it rides like a 404,” says Jason Fowler, Zipp wheel category manager. “We wanted to give athletes one go-to wheel they can ride no matter what the conditions…If you buy a set of aero wheels and you leave it in the trunk of your car [on race day] because you can’t handle them in crosswinds, that’s a waste of your investment.”
Copyright © 2016 Rodale Inc.