Rule 28, a UK-based manufacturer of aerodynamic clothing accessories, has released its latest aero sock.
Boldly, it claims they are “the fastest aero socks in the world” and could save you over 12 watts versus a standard pair of cycling socks.
The socks comprise a standard ankle sock sewn to an upper made of thin, textured Lycra, similar to what you might see on the sleeves of a fancy skinsuit.
It’s this upper fabric that affects your aerodynamic drag because the lower part of the sock is obviously hidden by your cycling shoes while riding.
The aero fabric isn’t quite as stretchy as you might expect though, so you do have to be careful putting them on (instructions are handily included) and there are internal silicone grippers to help them stay in place.
Similar to dimples on a golf ball, most aero socks work by using rough, textured surfaces or pronounced, strategically placed seams to generate a boundary layer of turbulent airflow around your leg. This reduces the size of the low pressure wake behind your leg and, in turn, reduces your aerodynamic drag.
Rule 28 claims this new sock also bests aero socks from leading competitors such as Nopinz, Castelli, Velotec, Kalas and Defeet.
Aero socks? Really?
It’s usually at this point that we’d advise taking these kind of outlandish-sounding manufacturer claims with a healthy pinch of salt.
While it’s probably best to keep the salt close by, Rule 28 has made the data behind its claims publicly available on its website, so we can attempt to draw our own conclusions.
Rule 28’s test was conducted in the Silverstone Sports Engineering Hub’s large wind tunnel, with a rider pedalling on a SwiftCarbon Neurogen time trial bike, and all tests were performed at 0 degrees yaw (which essentially means into a straight headwind).
It’s possible that changing the yaw angle could have affected the results, but Rule 28 told us it believes testing at different speeds with a fixed yaw angle provides more useful results than testing at a fixed speed over varying yaw angles, and this enabled them to test more socks with the wind tunnel time it had.
Though we’re admittedly not qualified aerodynamics experts by any stretch, standard industry practice for wind tunnel testing bike stuff has tended to be at fixed speed (usually around 45kph) and varying yaw angles in recent years. The obvious downside of that method of testing is that it leaves out the speed variable and Rule 28’s data makes it clear changing that can have a significant effect.
Therefore, an ideal solution might be to test at varying speeds and varying yaw angles. In fairness to Rule 28, though, wind tunnel testing is still costly and being a small company it clearly doesn’t have unlimited resources.
Digging into the data shows that there are naturally a few caveats, the principle being that the maximum 12.6 watts saving vs the standard baseline sock (which Rule 28 stated was a Morvelo Fluro sock) occurs at a speed of 60kph.
That may be a speed only a select few are usually able to achieve on anything other than long descents, but there are still gains to be made at slightly lower speeds.
The data shows savings are much lower at the slowest tested speed of 40kph, at just over two watts. Of course, 40kph per hour isn’t exactly ‘slow’ by most standards, and since the savings are likely to decline further at even ‘slower’ speeds these socks may be of little interest to riders who don’t race.
Savings do appear to increase significantly above that speed however (which is to be expected as aerodynamic drag increases at the square of speed), and it’s not unrealistic for a time trial or road racer to achieve speeds during races like those in the middle of the testing range.
For the racer obsessing over every watt, these may be a worthwhile investment. For everyone else, probably less so. I don’t expect to see my colleague Matthew Loveridge sporting a pair any time soon.
At £24.99, they are undoubtedly expensive for a pair of socks, but this price is in line with aero socks from competitors. An argument might also be made that in terms of £/watts potentially saved, they actually represent good value compared to the expense of upgrading components such as wheels, frames or helmets.
Readers of this website will no doubt be happy to know Rule 28 says the socks are fully compliant with UCI (Union Cycliste Internationale – the sports governing body) technical regulations. In a classically complex manner, Article 1.3.033 BIS dictates that socks “used in competition may not rise above the height defined by half the distance between the middle of the lateral malleolus and the middle of the fibula head”.
Fortunately, for those who don’t know where their lateral malleolus or the middle of their fibula head are, the UCI provides a handy diagram in its regulations and has even developed a tool for checking sock height at UCI sanctioned events:
— Jakub Zimoch (@kubawinter) July 7, 2019
Rule 28’s aero socks are available now from the Rule 28 website in UK sizes 3.5 to 12 and in white, black or with ‘calligraphy’ graphics.
A brief history of aero socks
At the end of 2012, the UCI banned the use of overshoes in track events. It stated overshoes were non-essential items of clothing designed purely to aid aerodynamics and therefore weren’t allowed under the regulations.
This ban has since been overturned because, well, it’s the UCI, but in the interim aero socks (and aero shoes) were developed to plug the performance gap.
This development thankfully also put a stop to cyclists wearing no socks at all. That initially became the default for many after overshoes were banned because bare skin is faster than standard cycling socks.
Early notable users of aero socks included Rohan Dennis, Alex Dowsett and Bradley Wiggins. All three used differing variations of aero socks to help them break the UCI Hour Record in 2015.
Aero socks would become popular in road racing too because, unlike aero overshoes, they don’t suffer the disadvantage of being overly hot and sweaty on warm days.