Gear News

Zipp launch 454 NSW wheelset with unique Sawtooth rim shape to improve crosswind handling

Radical rim shape undulates from 53mm to 58mm and is inspired by humpback whale fins

The launch of Zipp’s Firecrest rim profile in 2011 changed the way the bicycle industry thought about wheel aerodynamics and now the American firm has launched a technology it believes is equally as revolutionary. The new Zipp 454 NSW carbon clincher utilises an undulating 53/58mm-deep rim to create a wheel which is said to simultaneously reduce both aerodynamic drag and improve crosswind stability.

Stability is the key as far as the 454 NSW is concerned. Aero wheel manufacturers have long battled to marry high aerodynamic efficiency with low side force (or, in other words, the stability of the wheel in crosswinds) but Zipp say the 454 NSW is the first wheelset to truly bring the two together.

The combination of aerodynamic efficiency and stability is what Zipp call aero balance and the 454 NSW comes in with a claim as the “highest performing wheelset ever realised, with both aero-drag reduction and reduced side force at all wind yaw angles.”

Stability comes from the undulating Sawtooth shape which, combined with the rim’s HexFin dimple pattern, is said to improve handling in gusting wind conditions by helping to keep airflow attached to the rim, rather than detaching and creating additional turbulence.

The Sawtooth rim shape of the Zipp 454 NSW wheelset is inspired by the tubercles found on humpback whales

Aero balance

We attended the launch of the 454 NSW’s in London and, from the outset, it’s worth saying this is cutting-edge technology – with a sky-high price to match. £3,500 for the wheelset. The 454 NSW has been developed out of Zipp’s top-secret development hub in Indianapolis, Indiana, where engineers seized upon the emerging science of biomimicry to inform the four-year development of the rim shape.

First, however, some context. Zipp launched the 1080, a 108mm-deep wheelset aimed at the triathlon market, back in 2008. It was very fast, but also very unstable, Zipp say, and it got their engineers thinking about aerodynamics in a different way. It was the firm’s ‘first miss in the market’, admits Michael Hall, Zipp’s advanced development director.

The Firecrest rim followed and improved both aerodynamics and stability, thanks to its consistently wide rim shape and U-shaped spoke bed, at odds with traditional V-shaped aerodynamic rims. The Firecrest shape is now one mimicked across the industry but Zipp still saw significantly room for improvement.

“All of the rim shapes on the market, both our own and competitors, have high side force and low aerodynamic drag [on a deep-profile rim], or higher aerodynamic drag and low side force [on a shallow rim],” says Jason Fowler, Zipp’s wheel product manager. “What we wanted was to reduce both aerodynamic drag and side force simultaneously.”

Learning from nature

Zipp turned to nature – or biomimicry – for the answer. “Nature solves some of the most complex problems for humans,” says Fowler, and that proved the case for the 454 NSW.

The tubercles of a humpback whale provided the inspiration. The tubercles (essentially the large bumps on the whale’s flippers) improve the agility of the whale – a nine metre humpback whale can turn on a five-foot radius – by channeling water flow into narrower streams as it takes sharp turns in the water to catch krill.

“We saw that and thought it was a similar thing to what we were trying to do with our wheels,” says Hall. “How can we mimic the tubercle behaviour and put it on a rim to create the same sort of agility and efficiency?”

The Sawtooth profile is the answer. The 5 in 454 NSW refers to the difference in the height of the rim – 58mm at its deepest and 53mm at its shallowest – and the shape, or more specifically the raised parts of the spoke bed named HyperFoils by Zipp, is designed to work in the same way as tubercles by keeping the air attached over key parts of the rim, rather than swirling off.

It also works in a similar way to vortex generators on an airplane wing. The tabs on the wing, which are slightly askew to the wind direction, create a pocket of low pressure to one side, and this helps to keep the flow attached to the surface. Zipp have taken this a step further by increasing the prominence of the HyperFoil node as it as moves through yaw (wind) angles.

To get even more techy, the HyperFoil nodes are aided by the hexagonal HexFin ABLC dimple patterns (the dimples are round on Zipp’s other wheels) placed strategically on the rim, again to streamline airflow and further helping to improve stability in windy conditions.

Testing, testing

Zipp say the result is a five per cent reduction in side force compared with the ‘closest 60mm competitor produce’ and a 15 per cent reduction in crosswind feedback through a range of yaw angles referred to as ‘normal riding conditions’.

The 454 NSW rim shape also offers a claimed three to five watt reduction in aerodynamic drag, according to Zipp, but they’re keen to stress the biggest gain comes in the improved stability of the wheel, and how it will allow the rider to ride with confidence and remain in an aerodynamic position, regardless of the conditions. After all, it’s the rider which has the biggest effect on drag.

Claimed weight for the wheelset is 1,525g

It’s a wheelset which, according to Zipp, offers the performance of the existing 404 hoops, with the stability and handling characteristics of the 45mm-deep 303 wheelset. On top of that, it allows a rider to use a deeper rim in a far wider range of conditions, therefore taking advantage of the improved aerodynamics.

The 454 NSW was four years in development and during that time Zipp produced 36 prototypes and logged 252 hours of wind tunnel time – “we went crazy in the wind tunnel,” Fowler says – but real-world testing was also key to the development process. Zipp designed a wind sensor which integrated into a Garmin mount and this allowed them to collect in-ride data.

“It showed us that the position changes from crosswinds really have a significant impact in the overall speed of the ride,” says David Morse, an advanced development engineer for Zipp. “This is something we really couldn’t quantify before we took this to field testing in the real world. We’re showing stability has a tangible effect on your speed.”

The finer details

The 454 NSW is a completely new addition to the Zipp range but slots into the NSW (Nest Speed Weaponry) line-up of the company’s most advanced wheelsets. As a result, it borrows heavily from other technology developed for Zipp’s existing NSW hoops, as well as introducing the new Sawtooth profile.

That includes the Showstopper brake track, which combines a moulded-in, grooved brake track with embedded silicon carbide to improve all-weather braking performance. By our reckoning, it offers the best wet-weather carbon braking on the market based on our experience with the 404 NSW.

The wheelset’s graphics are also imprinted directly on the rim using Zipp’s Impress technology, so they “perfectly conform” to the dimples (and so don’t impact on their effectiveness), while also being “virtually weightless”.

The Cognition hub is said to reduce rolling resistance when coasting

The rim measures 17mm internally, with a maximum width of 27.8mm and a width of 26.4mm at the brake track. Zipp recommend the use of 23mm or 25mm tyres for maximum aerodynamic efficiency, though a 28mm tyre at the rear has a negligible effect on aerodynamics, while having the potential to improve comfort.

The 454 NSW also utilises Zipp’s latest Cognition hubset, which uses ‘Axial Clutch’ technology to allow the freehub’s ratcheting mechanism to deliver half the mechanical drag of conventional three pawl hubs, Zipp claim. The effect is reduced rolling resistance when coasting. The hubs are mated to the rims by Sapim CX-Ray spokes, with 18 at the front and 24 at the rear.

The wheelset is available now in clincher format only but it’s not tubeless compatible. Zipp say there isn’t a tubular version in the offing and a disc brake wheelset is a different aerodynamic proposition entirely, so it’s back to the drawing board for that one.

Finally, claimed weight for the Zipp 454 NSW wheelset is 1,525g (690g front/835g rear) and the wheels come with a rider weight limit of approximately 113kg (250lbs). They are available now, priced at £3,500 ($4000, €4000).

Website: Zipp
UK distributor: Zyro-Fisher