Tuesday, June 30, 2015

Bike fit, one step closer to the new bike

Last Friday I went to see Ben Williams at IT&B for a bike fitting session on the new Guru machine. I was so excited I forgot to get any pictures. Here is the one the Guru made; the computer is not much of a photographer.

This was the first time I ever tried the now classic aero position, the signature look of a time trial bike. This made Ben's job a lot harder. The process is something like an eye exam. Ben would direct the machine to move the seat or handlebar position up, down, forwards, and backwards, and ask me which way feels best. At first I found it impossible to say which was better because everything felt strange. Ben pushed everything out to the limits, where I clearly felt uncomfortable, then patiently homed in on a comfortable position.

Something I learned by reading various web sites -- mostly SlowTwitch -- was that most people end up with several frame sizes to choose from. A good resolution would be to pick one that is right in the middle of the adjustment range. In my case that turned out to be a Cervelo P3 size 56.

Bodies come in many different proportions. I have relatively long arms and legs. All my life I have struggled to find off-that-rack coats and long sleeved shirts that fit. Get the sleeves right and the torso looks like a flag on a flag pole. Get the torso right and the sleeves end halfway to my elbows. Ironically this long leg/short torso arrangement is supposed to favor runners. No sign of that in my case, at least not yet.

In the photo above you can see that my elbows are right at the pads and my upper arms are at almost a 45 deg. angle. This is a bit more angle than perfect, but if I come up too much (pull the arms back) my chest will open up to the air stream, producing massive drag. A lower bar would help here, but when Ben lowered the front I fell like I had too much weight on my arms, as if I was on the verge of falling over the bars. A person with normal length arms would be closer to a 60 deg. angle; I have seen some people at 90 deg. As with proportions, there is no single standard that works best. You have to try different positions until you find the one that works best for you. That may not be the position that produces minimum drag. Power generation and comfort are a big part of the equation. There is no point in riding in a radical position if you cannot hold it for the duration of your longest planned ride.

Knowing what size frame to buy is the first step in a long process. Next comes sifting through all the suitable makes and models. I am homing in on the P3, and have eyes for the new QuintanaRoo PRsix. Then there is the matter of mechanical vs. electric shift. What wheel set to use. Should I add on the power meter and make it a bundle?

Stay tuned.

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