Monday, March 4, 2013

revising position & design

During a ride yesterday Cara told me she thought my shoulders looked more relaxed than before. I'd been doing yoga recently and also had had a very nice massage at Doctor's Orders (World Gym, Potrero Hill). I have had a chronic issue with shoulder tightness for as long as I can remember: I tend to sit both on the bike and, more significantly perhaps, at a computer with my shoulders rolled forward. Stay in a position long enough the the body decides there's clearly some natural selection advantage to being there so semi-permanently adapts (this is over-simplistic, I realize). Anyway, I need to constantly focus to rolling my shoulders back, which is to say not roll them forward.

The consequence of this on the bike is if I have my shoulders rolled back that brings my chest forward. This means I bend in the hips, lowering my torso. But if my bars are so low my torso is already as low as it can go then this position becomes unsustainable. The only options are straightening my arms or rolling my shoulders forward again. Neither of these is a winning choice. It's certainly more racey to have a lot of handlebar drop but if you're cheating it by distorting your body to get your hip angle back where it has to be then there's no point.

So I raised my bars, pulling out some spacers and then flipping the stem. This felt better, like I had more room to move yet had no problem getting in a decent position. When I got home I photographed myself leaning against a wall, which admittedly introduces a distortion, and compared with a similar photo I'd taken in Jan 2010. The photo from Jan 2012 had tan lines and looked generally fitter than the one from Mar 2013: it was sort of depressing comparing my pasty present self to my rather fit-looking self from 38 months ago. So I blacked out the present image to focus on the outline.

The positions matched up fairly close. Key was with the higher bars my shoulders were rolled further back, which effectively shortens my arms, but keeps my back in the same place. The Slam That Stem crowd would be appalled, but I'm convinced the new position is better.

As I noted, I was playing with a BikCad design of a randonneuring bike. I increased the seat tube and top tube lengths of the new design and put it up against the silhouette and the new position (using the hoods here instead of the drops, to avoid handlebar shape issues) matches fairly well.

revised design

The key issue about this design is a rather steep (75 deg) seat tube. I like riding with a fairly short set-back so no reason to design a frame to handle large set-back. A steeper seat tube opens up clearance for the rear tire and allows for potentially shorter chain stays. However, with 42 mm tires and fenders this is somewhat limited by tire clearance, anyway.

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