DT Swiss, in partnership with SwissSide and tire manufacturer Continental, have announced a new set of tires called the Continental Aero 111. DT Swiss has been working on this for about 10 years in collaboration with SwissSide. Continental was a logical partner to bring this product to market. At a recent product briefing, they referred to this breakthrough as “the first ever aero tire.” Worn on Decathlon’s AG2R bikes at the Tour de France, the tire will be available at selected retailers from today in two sizes: 26mm and 29mm. The price is nearly 30-40% more than Continental’s other racing tire offerings, which come in at $120.95 USD.
An important note is that the tire is intended for the front wheel only. You can put one on the back, but you won’t get the same benefits. This tire can be installed on any wheel as the upgrades are not specific to DT Swiss wheelsets. However, DT Swiss wheelsets and this tire are designed together as a system. DT Swiss has options to bundle tires when ordering their wheels.
The message delivered during the conference was that it’s all about aero. Many of us think that aero only applies to people traveling at 45 km/h (28 MPH) and above. There are features of this wheel that make it attractive to amateurs and professionals alike, with a speed range of up to 30 km/h (19MPH).
We will examine the benefits of these new tires. We’ll be comparing them to what is believed to be the fastest current tyre, the Vittoria Corsa Pro Speed. At the time of publication, we have yet to get our hands on the product, but samples should be arriving soon. In a later article, we will do an analysis with the numbers provided by DT Swiss and other sources of tire performance data. I believe that many of these claims can be tested under real world conditions.
Rolling resistance
When discussing tire performance, we tend to talk more often about rolling resistance. Sites like Bicycle Rolling Resistance provide data on a Coefficient of Rolling Resistance (CRR) and we can easily figure out how many watts faster one tire is rolling than another. BRR data isn’t perfect, but a good data point around which to have a performance conversation. The recently released Vittoria Corsa Pro Speed tops the list. The Continental 5000 TT TR is also a top 10 contender and the GP 5000s TR is in 12th place.
We chose to use Vittoria as a comparison because it is #1. The other two Conti’s are used because the announcement doesn’t offer rolling resistance data, but says things like “expect it to be between this tire and that tire” on several fronts.
At 36 km/h (22.5 mph), the Vittoria will require 19 watts to rev, compared to 23 watts for the GP5000TT and 26 watts for the 5000. A 7 watt spread is considerable.
Aero 111 tires share technology with other Conti tires, so their performance is predictable. Conti claims rolling resistance for the tires is between that of the 5000TT and 5000S. The Aero 111 tire uses the same black burn compound known for grip and rolling resistance.
If we average the two tires and compare them to the Vittoria at different speeds, we see that the Corsa Pro speed still has an advantage of about 5w in terms of rolling resistance.
Durability and puncture resistance are closely related to rolling resistance. Manufacturers may choose to fit less tread or make tires thinner to improve rolling resistance. BRR scores puncture resistance and gives a score of 34 for the 5000s, 33 for the 5000TT and 25 for the Vittoria. Higher is better, but how that translates in the real world is hard to gauge. Continental claims the new tire should be on par with the more durable 5000s. It is based on the same Vectran technology that is both lightweight and does not affect rolling resistance.
Aerodynamics and Performance
There’s been great discussion on the forum, with the likes of Xavier Disley sharing his thoughts on the trade-offs between faster spinning tires and running flat Ironman bike legs. But 5 watts is considerable. What if the performance gap was closed while maintaining high puncture resistance? Can aerodynamics close this gap? We rarely talk about the aerodynamic differences between the two tires. Tire width and its dimensions relative to the rim are known to be a factor, but we’ve rarely seen data that says, “this tire on a 28 is more aero than that tire on a 28”.
This time, it’s the biggest notification component. We’re also conditioned to think that aero benefits are especially important when you’re traveling at professional speeds like 45km/h (28MPH). With this announcement there are claims of significant aero savings at speeds up to 30km/h (19PMH).
Jean-Paul Ballard of SwissSide explained the theory behind this aerodynamic breakthrough. Basically, if you can induce turbulence on the rim, the air will “stick” to the rim and generate less drag. If you look at the tire you will see patterns that appear etched into the tire and these little features are called “vortex generators”. They experimented with the size of these features and their positioning, depth, and arrived at a solution that they claim is right. These features condition the air flow to achieve the desired effect.
You can’t discuss aero without considering yaw. Yaw is the angle at which the wind is hitting the rim/tire. 0 Bending is head to toe, negative coming from the drive side and positive coming from the non-drive side. The effective yaw angle will depend on the direction of travel, your speed, and the direction and strength of the wind. The faster you go, the smaller the apparent yaw angle will be. There is a common belief that at the speeds World Tour riders are going, the yaw angles are very small. The reality after testing in Arizona on days with brutal crosswinds, even the pros look bad. If you plug in and analyze the data from the Kona, you’ll quickly see that the yaw is real and needs to be taken into account.
A great primer for the conversation is this Slowtwitch article from 2016, which explains how various parties tried to evaluate the override.
How you weigh the probability of seeing different cornering angles will determine how noticeable these tires are. The manufacturer claims that from 0 to 10 degrees (and from 0 to -10), these tires perform in a very similar way to the 5000TT or 5000s. However, at 10 degrees and beyond is where the magic happens. Some of the sources discussed in the ST article seem to agree that on a course like Kona, a large percentage of the time will be spent between -10- and 10-degrees, but somewhere around 28% of the time will be higher. (It is interesting to note that the outlier in 2016 was SwissSide which claimed to have spent some time above 10 degrees.)
The media kit provided several tables to help quantify the savings on the plane. They provided data at 30 km/h and 45 km/h and showed the “aero watts” required at various turning angles from -20 to 20 and compared the Aero 111 and the GP5000. The two tires run very close from -10 to 10 jaws. Beyond these points, they differ, the Aero 111 needs less aero watts.
At 45 km/h, the new tire will “float”, providing thrust – at least, on the DT Swiss wheel. They also gave data on the wider 29mm tire at 30km/h. And there were some comparisons with other tires. Unfortunately, the Corsa Pro Speed was not one of them. At 30 km/h (19 MPH) at 20 degrees, there is roughly an aero gain of 4 watts, which is significant at such a slow speed. At 45 km/h (28 mph) that translates into an incredible gain of 17 watts at 20 degrees. It should be noted, these numbers are visually interpolated from the charts provided.
So how much would you tend to save on a typical Ironman? This is very course dependent. But we go back to the 2016 article, one source claims about 28% of cases. If we take the data provided by DT Swiss and apply a distribution of deflection angles reported in that article, we see an average saving of somewhere around 3 watts. We have closed some of the 5 watt rolling resistance gap. At slower speeds, such as speed 30 km/h, the savings in watts are smaller, but the probability of seeing 10-20 degrees of yellowing is much higher, so the probability of getting full benefit is higher. When we do the road tests we will try to quantify this.
An important consideration that is difficult to quantify is how these tires affect handling. Jean-Paul Ballard explained that in crosswinds, the force we feel resulting in difficulty steering is actually the detachment and reattachment of air to the rim. These new tires, by keeping the air attached to the wheel, should result in much smoother handling, allowing us to handle deeper-section wheels and never have to go aero to do so. The claim is that you “just feel it” as you ride the tires. We can do better than that: it’s something we’ll be able to measure on the road with a gyroscope measuring around the steering column.
A question raised at the conference was how tire wear affects aircraft profitability. The response was that Decathlon/AG2R has been riding these tires for a while, and that they brought 2/3 worn tires back to the wind tunnel and saw no degradation of airplane performance. They quoted the 2/3 mark to be around 2500 km / 1550 miles.
Finally, the tires work with both hooked and hookless wheel systems. They said hookless provided no additional aero benefit and hookless testing is done entirely by Continental.
CONCLUSION
I’ve thrown a bunch of watts at you and the bottom line is how fast will these tires get me to the finish line and will I puncture to get there. Well, like all things aero, “it depends”.
First, we need to see how all these numbers play out in the real world. BRR numbers are great, but not on real tarmac. Second, we need to see how the aero manufacturer claims from the wind tunnel on the road. And finally, we need to test these claims in real wind conditions. Since starting to measure deflection on the open road, I’ve seen higher numbers than I was previously led to believe.
Do we have a new #1 in tire performance? Hopefully we’ll get a chance to confirm some of those things in the real world.
You can find the ongoing discussion about this new tire in our Readers Forum here.
Photos, graphics courtesy of Continental / DT Swiss / SwissSide