Reynolds RZR 92 wheelset
Reynolds RZR 92 wheels
Reynolds new RZR 92 wheelset is one of the most advanced - and expensive - wheelsets to have ever been created. Each set takes around 60 man hours in labour to make.
The RZR 92 wheels' creator, American composites expert Paul Lew, recently visited the UK to talk us through the wheels' features and why he thinks they are the fastest set of hoops currently on the market.
Firstly, the RZR 92 name is derived from the depth of the carbon rims - 92mm. This is a significant increase on some of the other direct competitors at this end of the wheel market, namely the 80mm rims on Zipp's 808 Firecrest wheelset, although a pair of these will set you back around £2,100. Lew reckons the RZR 92's are worth 20W at 50km/h compared to the 'nearest competitor'.
The deeper rim has come about due to an increase in rim width to accommodate 19-22mm tubulars with no significant difference in drag. The rim bulges out slightly a third of the way up before tapering to the spoke face in an aerodynamic profile. This increases the aerodynamic properties of the rim in a wider angle of yaw than flat-sided models.
Reynolds claim that the RZR 92 rear wheel is faster than a disc wheel. This claim, they say, is backed up by extensive computational fluid dynamics modelling and then validated in wind tunnel tests.
Lew (pictured right), who now works for Reynolds as its director of technology and innovation having started in wheel design in the late Eighties, is adamant that wind-tunnel testing of wheels isn't the be all and end all of aerodynamic design.
"While I have spent hundreds of hours in the wind tunnel, I personally find that wind tunnel testing is over-rated," Lew says.
"It's a component of overall design - wind tunnel testing is a validation tool."
Lew's theory is that you can test wheels in a wind tunnel, but in the real world they are fitted to a bike - a potentially vast array of bikes, each with its own aerodynamic characteristics that will affect airflow around the bike and wheels.
"Wheels don't race on their own without a bike and a cyclist, so I don't like to test individual wheels. It's an unfinished story as there's no real world performance to back it up," says Lew.
One feature of the rear wheel that immediately strikes you is the third, central flange - which Reynolds call the 'torque flange'. The two outer flanges feature a radial spoke pattern, with the central flange running directly in line with the rim face. There is no tension on the spokes, unlike conventional steel spoked wheels which can have up to 20kg load per spoke.
All of the spokes are bladed all the way to the rim, again to maximise their aerodynamic property. Each spoke includes a double strand of Kevlar, so that if they do break they will not become displaced, and because there is no load in the spokes the rim doesn't become deformed if several spokes break. Spokes can be replaced at the Reynolds factory.
Bearings are another area of wheel design in which Lew is flying in the face of fashion. "We will continue using steel bearings rather than ceramic as they have less rolling resistance. I think ceramic bearings are a waste of money for cyclists," says Lew.
"Ceramic bearings are only valid for one race as the balls become chipped, and once that happens any rolling resistance advantage goes."
The rims use Reynolds CTg (Cryo Glass Transition Temperature) braking surface for use with its Cryo Blue brake pads. This braking system has been developed to minimise heat build-up under braking without unduly affecting stopping power.
Reynolds are claiming a weight of 1452g per pair of RZR 92s. They are UCI approved.
Priced at £4,800, cutting-edge technology doesn't come cheap, but Lew's next task is to transfer some of the key technology used in the wheels in a more affordable package. First up could be a system that uses similar rims with steel spokes.
Pricing: £4800 per pair, £2800 for rear only, £2000 for front only.
Reynolds wheels are distributed in the UK by Upgrade Bikes.
RZR 92 rear hub with three flanges, including centre 'torque flange'
Non-drive side of the rear hub clearly shows the radial spoking on the outside flanges with tangential spokes on the torque flange
Deep rim section
Paul Lew with the RZR 92 wheelset
Inside tech: Zipp reinvents the wheel