Quote:
Originally Posted by Grant-53
Picking the right bike is a bit more complicated than going to a store and picking the one that looks nice. Weather, terrain, and traffic density affect the type of bike whether hybrid, commuter, or road bike. Next is getting the frame sized properly for your body dimensions. I use Zinn Cycles online program for recommendations on frame, stem, and crank arm sizes. Gearing is a matter of plotting the steps between a suitable low and high. If you are in stop and go traffic without steep hills, an internal gear hub is easier to shift when stopped. I have a 24 spd Jamis Aragon 700C and a Huffy 3 spd 26" as favorites. The aluminum Jamis is great on hills and towing a trailer. The Huffy is slick in traffic. I have fairings and bags for both.
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Zinn's calculator is not too far off overall, but I disagree with the longer crankarm length (theory) that is a theme with Zinn. I still have a variety of crankarms here with some longer Bullseye 190's and then down to 152's. Over two years of using a variety of length adjustments on the powercranks and data from the Computrainer, I repeatedly found VO2max through the roof with longer cranks not to mention the aero disadvantage that accompanies them via poorer aero profile due to lower seat height. (This was also the experience of a few of my competitors at the time). My best years racing started as soon as I switched to the shorter cranks and making better use of the gears and decreased shorter crank circumference. With the powercranks and additional pedal weights, it was possible to actually pedal around the entire 360 circle, even in the full aero position. Not possible with the long cranks unless the front bars were raised. Almost 15 years later, the industry started gravitating that way (beyond the stock 175mm) and you could see the shorter ones being more readily available as opposed to the stock 175-ish ones.
Interestingly, like engines (with their bore/stroke ratio), people (with their leg length ratio) have a relationship when it comes to power output in cycling. When a longer crankarm is used and a higher cadence is desired, the footspeed is also considerably higher and the lower leg (and knee) get to deal with this increased speed as a result.....
On a downhill, "spinning out" was nearly impossible with the short cranks, no bounce either like with the long cranks..
Ok, sorry for all the blabbity, blab but I'm not convinced an optimal crankarm length can be based on a formula. There's way too many variables to include fast-twitch/slow-twitch as well as the actual event itself (distance/sprint/mountain/etc..)..... And then there's the rabbit trail of the KNOPS (knee over pedal spindle). It never ends!
~CrazyJerry