Your selection of bike wheels has a significant impact on your road-riding performance.
Thankfully, we’re here to reveal what you should look for in materials, rim depth and much more…
The importance of bike-wheel selection can’t be understated. Along with the tyres, it’s your connection with the road; it’s the foundation of the success of your ride.
So let’s start at the beginning and material choice…
ALLOY OR CARBON?
The bike industry, including Campagnolo, tend to make their rims from either aluminium or carbon. There are exceptions but, in general, aluminium rims are more affordable than carbon. That’s down to alloy being cheaper to produce than carbon. Savings in your pocket doesn’t mean a compromise in performance, however.
Take Campag’s entry-level Calima wheels.
The nature of alloy construction means they naturally flex a little more than carbon, cranking up compliancy.
The result? Greater traction, which is particularly important in the wet.
In the past, one of the downsides of alloy rims was weight. But times are a changing.
Advancements in material technology’s seen the likes of Campagnolo’s top-end Shamal Ultra come in at less than 1,500g for the pair.
Aluminium wheels like these are also incredibly comfortable – that’s something every rider, no matter ability or experience, is after.
So there are definite gains to be had from aluminium wheels. But there’s also a reason why the likes of Philippe Gilbert at Lotto-Soudal and 2020 Tour de France winner Tadej Pogacar at UAE Team Emirates are using carbon wheels from Campagnolo’s Bora range. And that’s because they’re fast – damn fast.
That speed’s down to rim depth and its increased aerodynamics. Numerous wind-tunnel studies have shown that in isolation, clamped into a bike or being ridden by a rider, deep-rim carbon wheels are faster than shallow-rimmed alloy wheels.
This is where we need to talk about a rider’s co-efficient of drag (CdA). This is a dimensionless number that relates to an object’s drag force to its area and speed.
This figure’s impacted by variables like bike position, what helmet you’re wearing and, of course, wheel selection.
Data shows that adding aerodynamic wheels can cut this CdA figure by around 3-5%. How does this manifest itself in the real world? If you’re strong enough to generate 350 watts of power, the free speed from aerodynamic wheels would increase speed from 44.6km/hr to 45.4km/hr. That’s a 1.63% increase.
In short, deep rims equal free speed. But, historically, this came at a cost and that was handling. The deeper the rim, the argument went, the more unpredictable the handling in cross-winds.
The profile of a wheel like the Bora WTO 60 (with 60mm-deep rim) delays the separation of airflow on the rims, making them more predictable; in fact, at certain yaw angles, the wind offers help rather than hindrance, resulting in the sail effect and, again, free speed.
Stiffness is also greater, making carbon wheels more responsive, which is particularly noticeable when sprinting or on out-of-the-saddle climbs.
AERO ON THE HILLS
Is there a downside of carbon wheels? Historically, that increased rim depth came with a weight penalty.
But again, advancements in material technology’s seen the likes of the Bora One 35 come in at a staggering 1,276g for the pair.
Why is weight so important?
Rotational’s weight suggested to be worth twice that of stack (frame) weight, so if the parcours is lumpy and twisting left and right, you’ll want a lighter wheel that cuts inertia and boosts acceleration.
Rim-depth choice often comes down to the parcours, ability of the rider and bodyweight.
But, in general, it’s been mooted aerodynamic gains trump weight gains up to around 5% gradient for a recreational rider and an 8% slope for a WorldTour rider.
And that’s why carbon rims are often the favoured choice for speed, providing slipstreaming benefits at a minimal weight.
Rim width’s also important in the search for peak performance. This ties in with studies showing that a 25mm tyre is around 7% faster than a more traditional 23mm tyre. This is partly down to a more aerodynamic seal between where the tyre meets the rim.
Suffice to say, Campagnolo’s wheels are designed to smooth out airflow at this key transition point. (As an aside, 25mm tyres have also been shown to have similarly low rolling resistance as 23mm but you can run a lower pressure, so adding comfort and reducing the chances of a puncture. They’re better for grip in the rain, too.)
CALIPERS OR DISCS?
We’ll finish off with a brief overview of the other considerations when it comes to wheel choice, starting with wheels for traditional caliper bikes or for more contemporary disc-brake bikes.
The key points here are that disc brakes are becoming more commonplace because of better braking. This is especially true in the wet.
Material choice also impacts brake quality. In the past, caliper-braking performance on carbon rims didn’t match that of aluminium rims.
This has improved significantly but it’s still accepted that disc carbon wheels are swifter stoppers than caliper carbon wheels. Because of differences in construction to counter the different loads applied to the wheel when braking, there’s a weight penalty with disc wheels.
But this is minimal.
For example, Campagnolo’s Zonda Disc Brake wheels come in at 1,675g for the pair while the caliper versions come in at 1,540g.
You also need to decide whether you’re choosing clincher or tubeless tyres. Clincher’s the more traditional tyre and inner-tube combo, while tubeless dispenses with an inner tube.
The stated benefits of tubeless are improved ride quality, lower rolling resistance and improved puncture resistance.
The invention of the 2-Way Fit technology means guaranteed rim compatibility with both clincher and tubeless tyres.
Spoke number and profile also affects your ride. This is worthy of a feature in itself but, as a snapshot, Campagnolo’s cutting-edge and trademark G3 design – as seen on a wheel like the Bora One 50 – increases energy transfer and reduces stress on the spokes.
It achieves this dual win by fitting twice as many spokes on the right-hand side of the rear wheel than the left.
One of the bonuses of this system are a dampening of vibrations, even for the slightly heavier rider.
So there you have it, the wonderful world of wheel selection.
Ultimately, what you choose will come down to your ambitions as a rider and, of course, budget.