Bicycle Fitting In the Mobile Wind Tunnel
Added: Thu. Dec 20, 2012 7:01am
Posted in: Cycling
I have written articles on two systems used to fit serious cyclists to their bicycles - the Retul fitting system and the Guru Dynamic Fit System. In both articles I pointed out that the most efficient way, albeit most expensive way, of being fit is in a wind tunnel. The advent of the world's first portable wind tunnel has changed that. Below is a copy of a post that I made on my Facebook page yesterday describing my, and my significant other's experience being fitted in the wind tunnel:
Today was a fascinating day in the mobile wind tunnel with expert bicycle fitter, Roy Foley
. I was not pleased with Rosie’s position on her time trial bike so I decided to give her a Xmas present of a wind tunnel bike fitting. I was also anxious to conduct an interesting experiment on myself in that as an avid time trial competitor and an aeronautical engineer by schooling, the subject of bike aerodynamics is one that I find fascinating. I’ve written articles on both the Retul & Guru Dynamic Fit System for “Florida Cycling Magazine.”
After the fitting on my new bike in the spring of 2011, which was expertly accomplished at Mark Yeager’s shop, St. Pete Bicycle & Fitness, I went on to set state time trial records at 5, 10, 15 & 20 kilometers and one national record at 5K. Along the way, I won numerous state titles and one national title. I not only turned top time of the day for all age groups at two state championship events, but also did the same at the nationals. Being well aware of the old adage, “If it ain’t broke, don’t fix it,” I approached the project apprehensive, but very interested in the experiment to see if one already riding quite efficiently could be tweaked and made even more efficient. The wind tunnel can measure very small changes, and very small changes can make substantial differences in aerodynamic drag - the phenomenon that slows a rider.
The results were phenomenal! By the end of the numerous runs in the wind tunnel, Roy tweaked me to the point that I had saved 111 grams of drag. For you home gamers, that translates to a savings of about 1.1 seconds for each kilometer raced. It also translates to a savings of 11 watts so I can attain the same speed expending 11 watts less allowing me to go faster when I expend the same power as before.
A change of as little as an eighth of an inch can make a demonstrable difference in the wind tunnel. In my case, there was no need for any seat height/fore-aft or stem length adjustment(s). My bars were put slightly closer together to the limit with no change, so they were returned to the original position. The only change that was necessary on my bike was the rotation slightly downwards of the aerobars that put my head in a much better, aerodynamic position, but that slight tweak made a substantial difference.
Rosie’s situation was nothing less than phenomenal – something that did not surprise me. She saved over 300 grams of drag from her previous position! That translates to 3 seconds savings for each kilometer and an amazing 30 watts of savings. She needed changes in seat height, fore-aft positioning. Handlebar position. In addition, she needed shims added to the interior of her shoes.
I also determined two things that were of interest to me. I wanted to see how the Kask Bambino helmet, the one worn by Bradley Wiggins in his Tour TT victories would work versus my full-sized Kask TT helmet. It turned out that the small Bambino helmet was much more efficient, especially as the yaw angles (crosswind) widened. I also tried the new Giro helmet, which was not as fast as the Bambino for me. Rosie tried numerous helmets including the Bambino, but her Louis Garneau helmet measured the fastest.
I chose the Assos Cronosusit as my TT skinsuit a couple of years ago based on its performance in various wind tunnel tests. Roy suggested that we look at the difference between my size Medium Assos and a size small Hincapie skinsuit. The Hincapie kicked its butt!! Now I need to find one for under $375!
Rosie and I are looking forward to the 2013 season of time trial, and for her also triathlon competition!
Here is a URL to the Mobile Wind Tunnel website:
Master bike fitter & coach Roy Foley not only brings his fitting expertise gained through years of successfully fitting racers, but Roy brings the perspective of a certified cycling coach and elite competitor to his arsenal of "make people go faster" weaponry!
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