These days the “bike bling” in and around transition is getting ridiculously good, the thirst for “free speed” is at its highest and massive advancements in the technology behind bike and gear aerodynamics is seeing bike splits getting smashed every season.
Once athletes have purchased the aero frame, the aero helmet and the aero tri suit, often the next “investment” made will be a set of super slick aero wheels. Therefore we are going to take a look at aero wheels and their advancement in technology and just how much time they can save you.
Where are the biggest Aero Savings
Road wheels are designed for riding in bunches or pelotons, so the aero performance of road wheels is neglected, they are also designed to achieve a minimum weight for a rider weighing approximately 85kg, so aero performance of the wheels is not critical to designers as 95% of riding situations will be in a bunch or peloton. When it comes to TT and triathlon wheels some wheel manufacturers believe that it is the rim design that makes for a fast wheel, however some companies like xtreme carbon believe that you must look at the whole wheel as an aerodynamic system if a wheel is to be truly fast, therefore considering the aerodynamics of the hub, rim and axel.
The enemy of any cycling athlete is aerodynamic drag and the largest factor that contributes to aerodynamic drag is the frontal area of the rider, bike and wheel system. The simplest method of achieving fast wheels is to reduce the frontal area of the bicycle wheel. Any reduction in frontal area of a bicycle wheel reduces the aerodynamic drag force as encountered by the bicycle wheel system as it moves through the air.
The calculated drag force of the bicycle wheel, is directly proportional to the frontal area of the bicycle wheel. Reducing the frontal area of the bicycle wheel (refer table below) will result in a significant reduction of the aerodynamic drag force experienced by the bicycle wheel, which is quantifiable via the drag force equation table.
Drag Force Equation Table
|Assume wheel ERD = 620mm||centreline to centreline Flange|
|Hub Variable (mm)||30||40||50||60||70||80|
|Frontal Area (mm2)||9300||12400||15550||18600||21700||24800|
Tyre choice and aerodynamics
The 23mm tyre is the standard choice for nearly every cyclist. Tyre manufacturers have a large range of 23C tyres for all triathletes and time trialists, however there is a movement being led by triathletes towards a 25mm tyre. Current research has shown that under normal riding conditions on roads there is no measurable change in rolling resistance in upsizing to a 25mm tyre. The benefits of a 25mm tyre are a more comfortable ride and a larger rubber footprint which translates into more stable handling.
Anecdotal evidence also predicts that a wider tyre allows for a better frontal pressure profile and hence airflow in the detailed region of the tyre and rim interface. Therefore wider rim profiles improve aerodynamics, increase the tyre contact patch for better cornering grip, decrease rolling resistance and allows the wheel to be more comfortably ridden at a lower tyre pressure. This is of course without even entering the Tubs vs Clinchers debate.
This season the Ultimate triathlon series is partnering with Xtreme Carbon Wheels. Their innovative new design boasts up to a 60% reduction in frontal drag. I for one raced at the Sydney Duathlon on the 60 Race Grade wheel in blustery conditions. I found these wheels super quick and handled brilliantly through the corners. These guys have just entered the race wheel market and have spent the last couple of years in r&d fine tuning these very fast and sleek looking wheels. They have two levels of wheel, the Enticer and the Race. The Enticer comes in a 60 and an 80 and the Race in a 60 and a 90 in both wheels the frontal area is just 9300mm2.
Check out https://www.xtreme-carbon.com/ for more information.