drag2zero and cycling weekly make some interesting claims….but is it true ( have they broken the laws of physics?)
I recently came across a claim from drag2Zero a reputable aero company making skinsuits and other products. They make an odd claim on their website which is repeated in cyclingweekly:
While most brands test at one single speed, Endura Drag2Zero® understands the critical variations in aerodynamic efficiency at different speeds and in different riding positions. A suit optimised for a TT rider, averaging 50kph in an aggressive aero position is not necessarily the fastest suit for a rider on a road bike, averaging 35kph.
What they then say is that their super fast super expensive Endura D2Z® Encapsulator Suit is optimised for speeds over 45kph. And they also claim their still very expensive Endura D2Z® Roadsuit is optimised for road racing position and a speed range of 32–50kph. CyclingWeekly has a feature on this and says the fast suit won’t work for slow riders…..
So my question is can any skinsuit or indeed any piece of aero equipement work specifically for slower riders vs faster riders (and visa versa)?
Lets Start Acknowledging the MAGNITUDE of Aero Gains will depend on….
- the prevailing wind =>bigger gains in head winds
- and air density =>bigger gains in high air density
- the size of the rider =>bigger gains in bigger (less aero) riders
- the position of the rider=>bigger gains on tops > hoods > drops > TT position
Aero Gains & Speed
But what about rider speed. There is a huge misunderstanding that aero gains are only applicable to fast riders. If you believe this, then answer this: at what speed do gains suddenly manifest? 35kph? 45kph? 50kph?
The truth is aero gains work at every speed on a continuum. In fact the slower you are then the more the gains in terms of time savings BECAUSE the modest % gain is multiplied by a long time on the course. So we can add
5. the speed of the rider=>bigger % gains at faster speeds.
6. the speed of the rider=>bigger time savings at slower speeds
I actually made a video about this here, explaining the above to Triathlon Taren who claimed that a disc wheel didnt work for slower riders (skip to 10mins)…..
Here is the chart illustrating time savings with a disc vs zipp 808 according to rider speed/power
Skinsuit Savings & Speed
OK so what about clothing. Could there be any reason why a skinsuit was somehow better or worse for fast riders? The only reason, is position. If the skinsuit was somehow optimized in a frontal position, but somehow terrible side-on then its theoretically possible that it would be good for fast riders because their effective yaw is lower (see fft.tips/wind to check this yourself).
However it would be very odd to design a “frontal” skinsuit and the effect would still be on a continuum, the skinsuit wouldn’t suddenly be terrible at slower speeds.
But wait D2Z produced a chart to prove their claims……..
Encapsulator Suit Wind Tunnel Chart
D2Z® Roadsuit Wind Tunnel Chart
Does their own data support the idea that specific skinsuits are required? I have merged the charts above and you discover the following……..
- Their data is hopelessly small in terms of sample size
- They didn’t test Encapsulator Suit at slow speeds < 48kph!!
- They didn’t test Roadsuit Suit at fast speeds > 50kph!!
- The axis is % drag reduction relative to some other baseline clothing NOT absolute CDA and the comparator varies by test
EVEN then, the faster the speed then the more then % drag reduction savings except for four competitors. road#B + road #C +TT#B +TT#C. Remember although some appear to do worst and higher speeds, its only showing a comparison of savings NOT raw savings. The graph is very misleading.
But what about Comfort?
So am I saying a skinsuit should be worn by everyone? No, not at all, you might prefer comfort & convenience over speed. A lot of pros don’t wear a skinsuit all the time. However, you can buy an “aero suit” which is basically tight bib shorts sewn into the back of the aero jersey with an excellent (but tight) fit. Most pros wear something like this, never baggy normal jerseys. Similarly Trisuits with short or long sleeves are increasing aero tested and these sometimes have full length frontal zips to aid changing in transition. They usually have a small seat pad which is fine is distance is short.
Basically this is a big fat myth…..there is no such thing as fast skinsuits specifically for fast riders, in fact skinsuits will save you more if you are big and slow (sorry! large CDA!).
Aero equipment and Skinsuits don’t work in u-shapes or v-shapes, they work on a continuum.
Attempts to convince us that expensive skinsuits or expensive disc wheels are only for fast riders are an exercise in sales hype….and its weird how those at the top have to always spend more isnt it?
If you want to simplify things, think about this: a poorly designed skinsuit (or wheel or frame or bar or socks or shoes or helmet) will be slow for everyone not just fast riders or slow riders. OK yeh its now #kindofobvious
A quality skinsuit will be fast for everyone not just fast riders
But sure buy whatever suits your riding style including comfort and fit and not just speed!