The race wheel business has become a booming one within triathlon, and for good reason: once you’ve bought a bike, the next product on the race-faster wishlist is usually a set of spanking new race wheels. Plus, there’s a sex appeal factor behind the purchase that cannot be denied. Ahh, but which ones? There’s the rub.
Picking that wheelset is no simple matter. There are lots of brands, lots of rim depths and lots of pretty decals. Should you go clincher or tubular? 60mm of rim depth? 100mm? Offset front and rear depths? Are you a small athlete? Is the course hilly? Windy? Technical?
To answer these questions, we spoke with Zipp Speed Weaponry aerodynamics engineer Josh Poertner, and Steve Hed of Hed Cycling (aka Lance Armstrong’s former aerodynamic guru). For the real world input, we chatted
with multiple Ironman winner Bella Bayliss, of Team TBB, and retired Ironman Hawaii Champ Chrissie Wellington for their experience on how to pick ’em.
From their invaluable insights, we broke down the variables into three categories: rider, course and technical considerations. Once you meld the three, you’ll find a wheel type that will be best suited to you and your race.
While the big, deep aero wheels that the pros ride may be the ones you want, they may not be your best pick, especially if you’re new to the sport, or if you’re a smaller rider, or not too competent at bike handling.
When the winds pick up, the increased surface area on deep race wheels act like a sail, the increased surface area making handling a battle. So while that may not be an issue for some athletes, smaller, lighter athletes or novice bike handlers may find deep-dish wheels a drawback: if you’re fighting to keep your bike in a straight line, you’re burning precious energy. Not good when you’ve a run off the bike to come.
“Much of your performance is based on mental focus, so you need to be confident mentally,” says Poertner. “I tell everyone from novice triathletes to the pros we work with that you want to be on the deepest wheel you’re comfortable riding.”
Poertner suggests that mixing wheel depths, typically combining a shallow, easy-to-steer front wheel with a deeper rear wheel – as former Ironman World Champ Craig Alexander often employs – can be extremely advantageous, and even confidence-inspiring. “Go as deep as you’re comfortable with – then go one deeper in the rear,” he continues. “It’s a race car concept, but a deeper rear wheel moves your aero centre toward the rear wheel, and in many cases it adds crosswind stability, since you’ve added a stabilising yaw force.”
But is it worth the effort? Ask Bella Bayliss, who considers wheel selection a key part of her race strategy. “When choosing a wheelset for races, my key considerations are weight and aerodynamics, but then I think about what the wind will be like in the race,” she says. “I’m very sensitive to wind – I hate the feeling of being blown about – so if there’s any chance of wind, I use a front wheel that has very little rim to it. For the back, I’m happy to use a 60mm deep wheel.”
It’s in this category where you can forecast your race-day wheel choice as soon as you register for the event. The primary considerations to take into account are balancing your need to be aerodynamic with your need to ascend without added weight, and also to descend with confidence.
What you need is to become a scout: check the course topography and elevation at the race website. Find a GPS map of the course online. This will give you an idea of what the bike course will present you with and you can then kit out your bike accordingly.
“Getting to know your course is paramount,” says Steve Hed. “People often can’t train on
the course, but with online services like mapmyride.com they can get a pretty good idea of what the hardest climbs will be – then try to find hills in their area to duplicate them. I can’t think of anything that can take more time off your race – you can literally find minutes.”
Poertner considers another element: while your race may have a few steep climbs that earn the race repute and will have you considering plain ol’ training wheels, don’t forget that the rest of the race course may be pancake flat. “You want that aerodynamic wheel for the rest of your race, which may be mostly flat,” he says. “Whatever time you save due to a wheel’s lighter weight on the climbs, you’ll give back in spades to aerodynamic disadvantage if you’re riding the rest of the race on flatter roads.”
This is the one that confuses many athletes but it’s really about personal choice – and also a little bit about how savvy a bike mechanic you are.
Your first move? Select a brand you’re comfortable with. That comfort may emanate from its cost but, price aside, research is your next consideration. Go for the one that you think is fastest; choose the brands that back their product with wind-tunnel data.
The next quandary is whether to select clinchers (which run the standard tyre-and-tube configuration) or tubular wheels, which feature a full carbon rim surface with a tubular tyre. Tubulars offer a great weight saving over the aluminium rim clincher, making them a popular choice among pros. For those who are intimately in tune with their bike and how it operates, tubulars are the way to go – particularly if you know how to change a flat tyre on the race course. Hed states, “Those athletes that want to understand how their bikes work, that know about glues, have practised with installing and removing tubulars. They’re tubular people.”
But don’t try to convince Chrissie Wellington. In her unparalleled race career, she used a standard clincher race wheel with a deep carbon aero-rim section for its greater ease of use in changing flats when compared to tubulars. What’s more, within their extensive range, her then wheel sponsor, Hed, featured wheels with wider brake track than normal, making for a wheel with smoother airflow from tyre to rim, as well as greater ride quality.
“When I was racing professionally, I trained with clinchers. The key benefit was purely peace of mind from knowing how to change one relatively quickly – provided the gas canister works!” Wellington says with a laugh (having lost some time due to a faulty canister on her way to Hawaii gold in 2008). “The spares could fold up into tiny little packets, as well as the advantage that came from the wider rim, which helped my bike handling and made me faster.”
Wellington could have had any wheelset she desired, but preferred to race clinchers because they’re what she trains on. And for you, it may be the same call: familiarity with how to change a tube in a standard clincher makes for one less thing to stress about on your big day.
And as both Hed and Poertner point out, while clincher race wheels may be heavier, the trade-off isn’t huge. “If you’re willing to give up weight for convenience, then you’re gonna do just fine with clinchers,” says Hed. “For triathletes, the difference in weight between the two isn’t going to mean winning or losing races – aerodynamics is.”
Adds Poertner: “The rolling resistance data shows us the best clinchers, with latex tubes, are on par with the best tubulars. The success of pros in Hawaii shows that clincher technology has come a long way.”
So with your races coming up, take every advantage you can and research your wheel choice. “Getting the right wheelset is the greatest upgrade you can make to any bike,” Hed adds. “But it requires some work on a triathlete’s part to choose the right ones for their requirements.”
So what does the future hold for race wheels? Have we reached critical mass or are the wheels going to get even faster? Poertner believes there are still boundaries to be breached in the quest for speed.
“I’d have said we were near the limit two years ago, and we’ve found another 12 to 14% savings since then,” Poertner says. “We’re also starting to really understand more of the bike/rider interactions, and are working on making wheels that work without penalty in any fork or with any tyre.
"If we’re near the edge and might not find lots more speed, perhaps we’ll be able to find more speed in non-optimal conditions.” In addition, aerodynamics aren’t the be-all and end-all. “We’re working on tuning the harmonics of the rim for optimal vibration damping,” continues Poertner. “I call this the ‘compression socks of the bike leg’, the idea that you can burn fewer calories and experience less muscle damage and fatigue through reduced shock and vibration. So maybe the drag only falls two percent next year, but maybe we further the other benefits – data shows that this technology improves cornering grip due to less tyre bounce – to create an overall faster wheel and better
“Then again there could always be another Sub 9 out there, a product that blows away all the conventional wisdom! Experiences like that make me realise that you can never afford to stop innovating, as you never know what may be right around the corner.
How does a disc wheel work?
Disc wheels are popular because, quite simply, they’re the fastest. A spoked wheel churns air like a blender, creating drag. But wind passing across a disc sees only a smooth, unbroken surface and passes along without any turbulent effect or drag – thus making you faster.
Some wheels, like those from Zipp, have a flat profile for a minimally invasive passage of wind, while others, like Hed, have a lenticular (shaped like a lens) design, capable of optimally handling and deflecting wind from a variety of swirling directions. While many discs like that of Hed are smooth for a clean flow of wind across its surface, Zipp’s 900 and Sub 9 discs take a different tack: theirs have dimples dotting the surface. And, like the surface of a golf ball, the dimples serve a true purpose: they help ‘trip up’ the boundary layer across the wheel’s surface, helping it stay adhered to the wheels and making for an even smoother wind flow. So why do disc wheels cost so much? Materials and engineering: large swathes of carbon cost quite a bit! As do hours of wind-tunnel time for those brands that care enough to prove their data – a true example of ‘you get what you pay for’.
Race wheels Q&A
Is aerodynamic performance more important than weight savings?
“We’ve done a ton of research on the weight-versus-aero crossover,” Poertner says, “and have found that the balance goes toward aero on something up to an 8% climb, and that a weight saving of 300g saves you just one watt. Cutting rotational weight is only important during explosive efforts, like an attack in the Tour de France. Since triathletes don’t experience that, aerodynamics is generally more important.”
Do you need to be super-fast (or producing a certain wattage) to glean benefits from aero race wheels?
“No,” declares Poertner. In fact, the slower you are, the greater the benefits of aero wheels. “The mathematical answer is that aero benefit holds at any speed. A wheel with 20% less drag at 30mph also has 20% less drag at 20mph – it’s only the gross data that’s different in terms of drag in grammes. But the relative percentage stays exactly the same.
“Actually, slower riders save more time because they’re on the course for a longer period. They’re saving fewer watts, but more time, especially relative to your competition. Race wheels may be worth a minute’s saving
for a guy riding 40km in an hour and 20mins, but the guy riding 40km in 50mins will save
just 12secs – aero savings are saving you time based on a time percentage.”
Why are disc wheels not permitted at the Ironman World Champs?
The prevailing winds, which blow from east to west across the Kohala Coast, have been known to quite literally blow athletes off their bikes and into the lava fields. So race organisers err on the side of safety and declare Kona a no-disc race.
Are discs detrimental in all wind conditions?
Poertner believes at certain angles, as tunnel testing has proven on Zipp’s Sub 9 disc, wind can create a propelling effect, providing thrust instead of drag. “The worst thing that can happen with a disc is if there is absolutely no wind. At no wind, there’s no penalty – but more importantly, there’s no advantage. With a 10° crosswind, a disc wheel is a huge advantage.”
How much air should I pump into my tyres?
It will vary with rider weight and conditions, but most pros will run a firm 110-120psi in their tyres on dry days (for lower rolling resistance) and will lower it to about 90psi when the roads are wet (to increase the tyre’s contact patch with the road). Tubulars are capable of handling pressures as high as 145psi for race day, but the higher pressure makes for a significantly rougher ride, especially over potted roads.