When the wire-spoked bicycle wheel was invented in 1870, not a lot changed for the following 100 years. Up until the 1980s, ultra-light box-section wheelsets, minimal spoke counts and narrow tubs were the pinnacle of racing performance. Then, towards the middle of the decade, riders, coaches and manufacturers started to cotton on to the importance of aerodynamics.
In 1984, Francesco Moser rode double disc wheels to his hour record before disc and deep-section wheels became commonplace on Grand Tours, especially on time-trial stages. With the advent of carbon-fibre technology, combined with the adoption of wind-tunnel testing and Computational Fluid Dynamics (CFD) modelling, the aero properties of all cycling components, especially wheels, underwent a revolution in the 90s and noughties.
Triathletes have always been early adopters of technology – witness Paula Newby-Fraser and Mark Allen both using aero tri-spoke wheels during the 1980s at Ironman Hawaii – and soon aero ruled across all cycling sports. As Jason Fowler, Zipp Wheel Product Manager, explains…
“From Zipp’s perspective, aerodynamics has always been more important than weight. There are only a few races in the world where weight trumps aero. Aerodynamics were primarily seen as a time-trial or triathlon need only. But in 2008–2010, Fabian Cancellara started to change that viewpoint by winning Milan San Remo on 808s and Paris–Roubaix on 303s. Our professional riders during that time could see the watt savings and realised the benefit. For those competing in the Tour de France, using aero wheels over a box-section aluminium rim was an extra rest day from a wattage and calorie-saving perspective.”
A race wheel is a highly complex component and is developed using a lengthy process of testing, feedback and refinement. Scott Nielson, vice president of R&D at Enve, describes the steps. “First we’ll identify the need for a product and then, using CFD and input from aero expert Simon Sharp, we’ll create a mountain of iterations. We’ll whittle those down to the best, develop prototypes and put those in the tunnel.
“We’ll then ride the wheels,” continues Nielson, “and give them to our sponsored riders for feedback on stability, handling, acceleration and how they hold speed. We’ll make some tweaks, then it’s back into the tunnel and crucially testing them with a number of top frames. Although it complicates the process, this step is vital; if the wheels aren’t tested as part of the whole system, there’s no guarantee they’ll work.”
All aero rims are not made equally, with narrow V-sections now aerodynamically usurped by wide and toroidal shapes. V-section rims are far cheaper to make and, when punching directly into a headwind – 0° of yaw – return decent numbers. Increase the angle of yaw, however, and handling can become a real issue. The bulge of a toroidal profile allows rims to perform and handle far better in real world 5-20° of yaw.
Top-end wheels will be all carbon, delivering the Holy Grail of low weight in combination with deep-section aerodynamics. Cheaper wheels combine an aluminium rim with carbon-fibre fairings bonded to them. Aerodynamically these can rival their costlier carbon cousins, but they’ll always be significantly heavier.
Any early adopter of carbon race wheels will remember the horror of cork pads on a wet day and, although carbon braking surfaces and pads have improved massively, they’re still not as reliable as alloy braking tracks. There’s also the potential for overheating and blow-outs. Again, this has improved but, if you’re riding anywhere with long descents, it does need to be considered.
Turbulence equals drag and rapidly rotating spokes create a hell of a lot of turbulence. Bladed spokes certainly help to slice through the air, but the fewer there are and the shorter they are, the more they’ll enhance the wheel’s aero potential. Fewer spokes can raise concerns about durability, but with deep-section wheels proving themselves at races such as Paris–Roubaix, these are now largely unfounded. A disc wheel is the ultimate extrapolation of spoke minimisation.
Let’s face it, hubs are nowhere near as sexy as rims, but without doubt the quality of a hub can make or break the performance of a wheel. There’s been a lot of fuss about ceramic bearings, based on the fact that ceramic can be made rounder, and therefore more smooth-rolling than steel, and that it’s harder and more durable.
The jury’s still out on the exact gains to be made but, whether you opt for steel or ceramic, quality is everything.
The tubs versus clinchers debate rumbles on yet, like for like, a tub wheelset will always be lighter. Whatever set-up you run, your choice of rubber will significantly affect how your wheels perform. The tyre profile should complement the rim aerodynamically, and there are a number of marginal gains that you can make to minimise rolling resistance. Using glue rather than tape for tubs, running latex tubes in clinchers and optimising your tyre pressure can all make
those wheels roll even more sweetly.
What to consider before purchasing race wheels
The wheels are one area where manufacturers of off-the-peg builds often save a few pennies. Even on top-end bikes, the rims are usually massively under-specced. Buying some race-day wheels can deliver an instant speed boost, but there are a number of factors to consider.
We’ve already mentioned the tubs versus clinchers dilemma and we’re not going to settle it here. If you’re going to train regularly on your race wheels, clinchers are probably the sensible choice for tyre wear costs and gluing hassle alone, but you’ll find plenty who’ll argue passionately in favour of tubs.
Probably your most important decision is what depth of set-up to opt for. The default aero choice is a deep-section 80-90mm front and a disc on the rear. It certainly can be a fast set-up but remember that cheaper V-section deep-rims can be a real handful in the wind, and if you’ve got Kona aspirations a disc is a no-no. A great compromise that’ll suit a mix of courses and conditions is a 80-90mm on the rear and a 40-60mm on the front. Not surprisingly, our industry experts have their own thoughts.
Jason from Zipp opts for a deep rear and shallower front. “I use a 404 Firecrest carbon clincher on the front and a 808 Firecrest carbon clincher on the rear. It’s the best all-round wheelset for the racer seeing a variety of courses and conditions. The clincher option will allow you to change tyres based upon course conditions.”
Scott from Enve has a few options. “There’s a real misconception that deep-section wheels are hard to handle in the wind and don’t perform on hilly courses. I rode 8.9s at Ironman St George, which is hilly and windy, and they were really fast. 6.7s are great all-rounders but, for a tiny drop in aero performance yet significant weight savings, our new 4.5s are superb.”
RACE VS TRAINING USE
So, you’ve got your super-fast race wheels. Now: do you train on them or keep them wrapped in cotton wool for race-day use only? “I’m a big believer in training on as near to race-day set-up as possible,” adds Scott. “By putting in the miles using your race gear, you’ll iron out the kinks in your set-up and become 100% comfortable and confident in how it performs. Your bike will handle differently with race wheels on. Do you really want your first experience of dealing with a tub flat to be in your season’s A-race? Carbon race wheels can certainly handle rough roads, their use in the Spring Classics and by cyclocross racers is testament to this. I’m not saying to abuse them, but you don’t need to mollycoddle them either.”
Finally, if you switch between alloy training wheels and carbon race wheels, don’t forget to swap your pads. There are dual compound pads, but still keep a set for carbon and a set for alloy.
The future of race wheels
Trying to gaze into the crystal ball of race wheels, the burning question is whether they can get any faster. Enve’s Scott Neilson believes there’s room for improvement. “The work, tunnel time and R&D of a few companies has launched a lot of new companies that, by using prior learning, already have a foot in the door. And that really drives us. We’re in the tunnel seven times a year, saving athletes watts, and there are still gains to find, new shapes to try and advances to make.”
Although such legitimate imitation is the greatest form of flattery, illegal counterfeiting is a dark side that Neilson believes customers need to be aware of. “We buy these fake and unbranded wheels and test them. They may look really similar and seem like a tempting deal but, from a structural standpoint, they’re potentially very dangerous to ride.”
Zipp’s Jason Fowler agrees that there’s more speed to be found. “Wheels can get faster, but faster doesn’t always mean aerodynamic drag. Fast can also be a more stable wheel (using less energy to go in a straight line) and brake performance (more stopping power allows you to brake later). We have started to push this envelope with 404 Firestrike.”
A big factor will be the adoption of disc brakes on the road, which both of our experts view as being inevitable. Fowler sees them as a potentially exciting proposition. “Disc brakes certainly open the door for what is possible in terms of rim shape since the chainstays are wider and you don’t have to accommodate a brake caliper.”
Finally, and just to add more confusion to the tub versus clincher debate, Neilson imagines a future for tubeless technology on the road.
“Tubeless sits somewhere between tubs and clinchers, delivering some of the ride characteristics of tubs but with the convenience of clinchers. We could have launched a tubeless road wheelset a long time ago, but we wanted to make sure it was 100% viable. It’s only recently that more tyre choices have become available
and you don’t have to make compromises.
“With the current leaning toward wider higher-volume tyres, though, running tubeless with sealant could make sense for racing,” Neilson continues. “There’s enough air volume to seal a puncture without having to stop or just requiring
a quick top-up.”