Calnago wrote: ↑
Sat Oct 19, 2019 8:50 pm
...Slower riders get more seconds on course saved for going aero.
Specialized was really reaching deep when they spewed out that nonsense to try to convince people that no matter how slow they go, aero counts. And the slower you are, the more time you save.
Please... at some point you just have to say “Whaaaat...?” Lol
Group waiting for “AeroBob” at end of the ride: “Hey Bob, we were just about to come back looking for you, did you get lost or something?”
AeroBob: “No, I was just going slow to save even more seconds with my new aero bike”.
You are joking right? How do you argue with physics? I did some rough math, so don't be too hard on me.
I am glad you mentioned aerobob. Good guy.
Aerobob and his identical twin brother aerosteve are in a 100km race on idential tt bikes. Aerosteve can crush out 331w on average at 45km/hr. He is a monster. (Some think he is on the juice...)
Aerobob only puts out 250w average. What a loser. Aerosteve crushes his time on course.
So they repeat the same race, but they each have a great new confabulator helmet that magically saves each of them 10w. Aerosteve is now just under 1.5 minutes faster. Aerobob, the slowpoke he is, is now 2.2minutes faster. Aerosteve still wins the race by a landslide, but aerobob had more to gain from that 10w saved because that 10w represented a greater proportion of his total power. His percentage of savings was higher vs his power output.
Now it is not that easy. The confabulator helmet may save 10w at 45km/hr, but if you math it out... it only saves 7.29w at aerobobs speed of 40.5km/hr (speeds are pre-confabulator). That is worth 1.6 minutes for aerobob. Compare that to 10w saving for aerosteve at 1.5minutes saved. Aerobob, as slow as he might be, gained more from that confabulator helmet, even at his slower speed. Even when the aero gains from that helmet were corrected for his lower speed.
So why is this? Well, That is the exponential nature of drag. Air resistance is proportional to velocity squared.
Still don't believe physics? Lets look at aerojeff. His average speed is a pathetic 30km/hr over that 100km race. That 10w confabulator helmet at 45km/hr is only worth 2.96w at 30km/hr!!! How much time does aerojeff save on course with the confabulator?!? 2.05 minutes. Or just over 30s more than "mr 45km/hr" aerosteve saves with the same helmet.
The math gets even more complex as we get towards 15km/hr, as things like crr become a bigger player at those speeds. that is where the rough rule of thumb of "at speeds over 15 km/hr, aero becomes increasingly more important than weight or crr." comes from.
So what i say to people is... if you are slow, dont sweat aero. You will see gains, but you probably dont care anyway. If you want to be fast, aero IS (almost) everything. The faster you go, the more it matters.
Me and a local rider have near identical ftp. But on the climbs i crush him because i am lighter, and on the flats i crush him because i am more aero. And that is with my un aero road bike (aero wheels only, but low position, aero helmet and jersey). On my tri bike on the flats... i am in another stratosphere. When we rode together and i dropped him frequently, he said "i need to get me some of that aero shit".