DT Swiss, in collaboration with SwissSide and tire manufacturer Continental, has announced a new set of tires, the Continental Aero 111. DT Swiss has been working on this for about 10 years in collaboration with SwissSide. Continental was a natural partner to bring this product to market. In a recent product briefing, they called this breakthrough the “first ever aero tire”. The tire was spotted on Decathlon AG2R bikes during the Tour de France and is available from select retailers starting today in two sizes: 26mm and 29mm. The price is almost 30-40% higher than Continental’s other road tires, at $120.95 USD.
An important note is that the tire is designed for the front wheel only. You can put one on the rear wheel, but that will not provide the same benefits. This tire can be mounted on any wheel, as the improvements are not specific to DT Swiss wheelsets. However, DT Swiss wheelsets and this tire are designed together as a system. DT Swiss offers options to bundle the tire when ordering their wheels.
The message that was conveyed during the briefing was that it is all about aerodynamics. Many of us think that aerodynamics only applies to people who ride 45 km/h (28 MPH) or faster. There are features of this wheel that make it attractive to amateurs and professionals, with a speed range of only 30 km/h (19 MPH).
We’ll be looking at the benefits of these new tires, comparing them to what is considered the current fastest tire, the Vittoria Corsa Pro Speed. At the time of writing, we haven’t gotten our hands on the product yet, but samples should be arriving soon. In a later article, we’ll do an analysis using figures provided by DT Swiss and other sources of tire performance data. I believe many of these claims can be tested in real-world conditions.
Rolling resistance
When we talk about tire performance, we usually talk about rolling resistance. Sites like Bicycle Rolling Resistance provide data on a coefficient of rolling resistance (CRR) and we can easily calculate how many watts faster one tire rolls than another. BRR data isn’t perfect, but it’s a good data point 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 sneaks in at #12.
We chose to use the Vittoria as a comparison because it’s #1. The other two Contis are used because the listing doesn’t include rolling resistance data, but does say things like “expect it to be between this tire and that tire” on various fronts.
At 36 km/h (22.5 MPH), the Vittoria needs 19 watts to roll, compared to 23 watts for the GP5000TT and 26 watts for the 5000s. A spread of 7 watts is significant.
The Aero 111 shares technology with other Conti tires, so their performance is predictable. Conti claims the tires’ rolling resistance is between that of the 5000TT and 5000S. The Aero 111 uses the same Black Chili compound known for its grip and rolling resistance.
If we take the average of the two tires and compare it with the Vittoria at different speeds, we see that the Corsa Pro Speed still has an advantage of around 5W in terms of rolling resistance.
Durability and puncture resistance are closely related to rolling resistance. Manufacturers can choose to use less protection or make thinner tires to improve rolling resistance. BRR rates puncture resistance, giving a score of 34 for the 5000s, 33 for the 5000TT and 25 for the Vittoria. The higher the better, but how this translates to real-world conditions is difficult to judge. Continental claims the new tire should be comparable to the most durable 5000s. It is based on the same Vectran technology, which is both lightweight and has no impact on rolling resistance.
Aerodynamics and performance
There have been some great discussions on the forum, with people like Xavier Disley sharing his thoughts on the trade-offs between faster rolling tires and getting through an Ironman bike leg without a flat. But 5 watts is a lot. What if the performance gap could be closed while still maintaining superior puncture resistance? Can aerodynamics close the gap? We rarely talk about the aerodynamic differences between two tires. Tire width and dimensions relative to the rim are well known factors, but rarely have we seen data that says, “this tire on a 28 is more aerodynamic than that tire on a 28.”
This time around, it’s the biggest part of the announcement. We’ve also been conditioned to think that aerodynamic gains are especially important when riding at pro speeds like 45 km/h (28 MPH). With this announcement, claims are being made of significant aerodynamic savings at speeds as low as 30 km/h (19 PMH).
Jean-Paul Ballard from SwissSide explained the theory behind this aerodynamic advancement. Basically, if you can create turbulence at the rim, the air will ‘stick’ to the rim and create less drag. If you look at the tire, you will see patterns that seem to be chiseled into the tire and these little features are called ‘vortex generators’. They experimented with the size of these features and their positioning, depth and came up with a solution that they claim is just right. These features condition the airflow to achieve the desired effect.
You can’t talk about aerodynamics without considering yaw. Yaw is the angle at which the wind hits the rim/tire. 0 Yaw is frontal, negative comes from the drive side and positive comes from the non-drive side. The effective yaw angle depends 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 of World Tour riders the yaw angles are very small. The reality after testing in Arizona on brutal crosswind days, even the pros see yaw. If you put together and analyze the data from Kona you will quickly see that yaw is real and should be taken into account.
A good introduction to the conversation is this Slowtwitch article from 2016, which explains how different parties tried to assess yaw angle.
How you weigh the likelihood of seeing different yaw angles determines how much these tires stand out. The manufacturer claims that from 0 to 10 degrees (and 0 to -10) these tires perform very similarly to the 5000TT or 5000s. However, it’s at 10 degrees and beyond that the magic happens. Several of the sources discussed in the ST article seem to agree that on a course like Kona, a large percentage of the time is spent between -10 and 10 degrees of yaw, but somewhere around 28% of the time is spent above it. (Interestingly, the outlier in 2016 was SwissSide, which claimed little time was spent above 10 degrees.)
The media kit included a number of graphs to quantify the aero savings. They provided data at 30 km/h and 45 km/h showing how many “aero watts” were required at various yaw angles from -20 to 20 comparing the Aero 111 and GP5000s. The two bands track very closely from -10 to 10 yaw. Beyond those points they diverge with the Aero 111 requiring fewer aero watts.
At 45 km/h (28 mph) the new tire will “sail” and provide thrust – at least on the DT Swiss wheel. They also provided data for the wider 29mm tire at 30 km/h (19 mph). And there were some comparisons to other tires. Unfortunately, the Corsa Pro Speed was not one of them. At 30 km/h (19 MPH) at 20 degrees of yaw there is about a 4 watt aerodynamic advantage, which is significant at such a low speed. At 45 km/h (28 mph) that turns into a massive 17 watt gain at 20 degrees of yaw. Note, these numbers are visually interpolated from the included graphs.
So how much would you save in a typical Ironman? It really depends on the route. But let’s go back to the 2016 article, one source claims around 28% of the time. If we take the DT Swiss data and apply a distribution of yaw angles reported in that article, we’re going to see an average saving of somewhere around 3 watts. We’ve closed some of the 5-watt rolling resistance gap. At lower speeds, like 30 km/h, the watt savings are less, but the opportunity for 10-20 degrees of yaw angle is much greater, so the chance of full benefit is greater. When we do road testing, we’ll try to quantify this.
An important consideration that is difficult to quantify in watts is how these tires affect handling. Jean-Paul Ballard explained that in cases of crosswinds, the force we feel that makes it difficult to control the wheel is actually the air coming loose and reattaching to the rim. These new tires, by keeping the air attached to the wheel, should result in much smoother control, potentially allowing us to drive deeper section wheels without having to get out of aerodynamics. The claim is that you “just feel” this as you ride on the tires. We can do better: it’s something we can measure on the road with a gyroscope that measures around the steering column.
One question that came up during the briefing was how tire wear affects aerodynamic advantage. The answer was that Decathlon/AG2R have been running these tires for a while and that they have taken tires that were 2/3 worn back into the wind tunnel and have seen no degradation in aerodynamic performance. They indicated that 2/3 point is approximately 2500km / 1550 miles.
Finally, the tires work with both hooked and hookless wheel systems. They said that hookless does not provide any additional aerodynamic advantage and that hookless testing is done entirely by Continental.
Conclusion
I’ve given you a lot of watts and the bottom line is how much faster do I get to the finish line on these tires and do I get a flat? Well, as with everything in aerodynamics, “it depends.”
First, we need to see how all of these numbers play out in the real world. BRR numbers are great, but they don’t happen on real asphalt. Second, we need to see how the manufacturer’s aerodynamic claims from the wind tunnel play out on the road. And finally, we need to test these claims in real wind conditions. Since I started measuring yaw rates on public roads, I’ve seen numbers that are higher than I previously thought.
Do we have a new #1 in tire performance? Hopefully we get a chance to confirm some of these things in the real world.
The ongoing discussion about this new band can be found here in our readers forum.
Photos, graphics courtesy of Continental / DT Swiss / SwissSide