Last month, the Cyclingnews tech workforce spent a day within the wind tunnel on the revered Silverstone Sports Engineering Hub, placing the WorldTour’s greatest superbikes by means of their paces in a head-to-head wind tunnel superbike showdown.
Alongside the 11 superbikes, with their common value nearing £10,000, we additionally had our ‘baseline’ bike`: A 2015 Trek Emonda ALR full with field part wheels, rim brakes, exterior cables, spherical handlebars, and completely no aerodynamic optimisation in any way.
As you’d count on, it was slower than the superbikes. In the uncooked knowledge, taking a mean of the 2 rider-on-bike assessments we did on the baseline bike (firstly of the day and once more on the finish), it was 23.06 watts ‘slower’ at 40km/h than the common results of our superbikes. What which means is in case you had been to attempt to trip at 40km/h, you’d must put out 23 extra watts on this bike than in case you had been on a mean superbike.
But all of our fashionable superbikes had been outfitted with deep-section aero wheels, so what occurs if we swap out the wheels on our baseline bike for the same possibility? We checked, in fact.
We needed to know the way a lot distinction the improve would make. Would it shut that 25-watt deficit fully? Would it make any distinction in any respect? Is it a greater bang-for-buck improve than, say, a brand new helmet?
Also, in case you personal an previous entry-level bike like our Emonda, is an aero wheelset improve place to spend your cash, or do they simply look cool? Let’s dig into the take a look at and discover out.
Our wheelset of selection was a reasonably budget-friendly possibility from a now-defunct British model Prime, an RR-50 V3 mannequin to be exact.
They had been 50mm deep, with an inner width of 19mm, and we mounted the identical 25mm Continental GP5000 S TR entrance tyre that was fitted to all different bikes on take a look at by the use of standardisation. Prior to the model’s closure, these wheels would retail for round £800.00 / $900.00.
The outcomes
We examined every bike at seven angles of yaw, which is the angle at which the wind hits the bike and rider. A yaw angle of 0 levels means the wind is hitting the rider straight on; an ideal headwind if you’ll. A better yaw angle means the wind is coming from the aspect on.
In this case, we examined from -15 levels (wind coming from the left aspect), by means of to +15 levels (wind coming from the appropriate), in 5 diploma increments for a complete of seven captures.
The knowledge supplied by the wind tunnel is CdA, which stands for Coefficient of drag x Area. The drag coefficient displays the form and the way simply air flows round an object, whereas the Area is just its dimension. The decrease the drag coefficient, or the smaller the thing, the extra simply it’s going to move by means of the air and thus, the quicker it is going to go for equal effort.
What’s actually attention-grabbing is that the deeper wheels had been really slower at decrease yaw angles. This is probably going as a result of wheels being considerably wider than our baseline wheels, and thus merely growing the frontal space of the bike.
However, because the wind comes from wider angles, the deep wheels come into their very own, providing extra of a ‘sail’ impact, catching the wind and serving to to propel the rider ahead.
Having averaged the CdA values from the uncooked knowledge, we discovered that with the deeper wheels, the rider-on-bike take a look at supplied a CdA of 0.3640. This is 0.0062 decrease (and thus quicker) than the baseline.
When you are taking these CdA values and calculate the facility required at 40km/h, we begin to get an thought of the distinction in a real-world setting.
We can see right here that our superbikes require a mean of 282.41 watts to trip at 40km/h. Our baseline bike, as defined earlier, is 23.06 watts. Interestingly, the aero wheels do not shut the hole very a lot in any respect. Ignoring our error margin (which we’ll get to beneath), the aero wheels are price simply 5.89 watts.
To assist contextualise that into the true world, that equates to a saving of 25 seconds over 40km in case you had been using at 250 watts, or a velocity achieve of 0.24km/h for equal effort. If you enhance your output to 350 watts, your velocity achieve climbs to 0.27km/h.
However, importantly, as soon as our error margin is taken under consideration, the wheels may really be equal. The error margin for our take a look at (which we calculated utilizing the distinction between the 2 assessments on the similar baseline setup firstly and the top of our day), was 3.91 watts.
As proven within the two bar graphs above, the error bars for the 2 related datasets overlap one another, so evaluating the best-case state of affairs for the baseline bike with the worst-case state of affairs for the deep wheels, there is a risk that the shallow wheels are quicker.
Of course, error margins can work each methods, so to flip that spherical and take the worst-case state of affairs for the baseline bike and the best-case state of affairs for the deep wheels, the distinction could possibly be as a lot as 13.7 watts at 40km/h.
Conclusion
Statistically talking, as a consequence of our error margin, we can not conclude with absolute confidence that the deep-section wheels are quicker than our shallow wheels.
However, wanting on the uncooked knowledge and utilizing frequent sense, we’re moderately assured that they’re.
From a cost-per-watt viewpoint, it is notable that the distinction is so small for an merchandise so costly. Using the uncooked knowledge, the saving is lower than six watts, and going off the retail value of £800 / $900, that is £133.33 / $150 per watt saved.
What’s extra, once we wind tunnel examined wheels in 2022, we discovered that the distinction between the perfect and worst aero wheelset was simply 3.87 watts and that there was no correlation with value. This tells us the extra financial savings to be discovered by upgrading to a ‘premium’ aero wheelset – as a substitute of our budget-focussed Prime wheelset right here – can be small.
Perhaps most attention-grabbing of all, although, is that given a lot of the distinction between our deep wheels and our shallow wheels is discovered at increased yaw angles, that are much less frequent than low yaw angles, the real-world saving is probably going even much less.
Of course, aerodynamic enhancements aren’t the one purpose to purchase a contemporary wheelset. Many of them are lighter in weight, wider and thus supply higher dealing with, and extra, but when your solely motivation for desirous to improve to deep wheels is an aerodynamic achieve, it is best to most likely suppose once more earlier than investing all that money… although they do look cool.