A Complete Bike Fit Calculator
I had recently spent a lot of time trying to figure out how to properly fit a bike. I had myself fit by a few different specialists at local bike shops, rummaged through a dozen cycling books, searched through numerous websites, and even read a few journal articles. (I know I’m crazy.) The most important and consistent thing between everything I found was the relative position of your knee over your pedals and the corresponding seat height.
Dr. Andy Pruitt, who regularly fits pro-cyclists, states that the seat height should be high enough such that your leg is nearly fully extended at the bottom of your stroke, with a very slight bend in the knee, and no hip rocking during pedaling. And, from the front of your kneecap, hang a plumb-bob and its point should be intersect the end of your crank in the horizontal position. This gives you the optimal lower body position for minimal joint stress and maximum power output for road racing. For off-road biking, he recommends to shorten the seat by about an inch, but maintain your knee-crank alignment. And, of course, everyone’s body is different and things can vary slightly.
As for the rest of the bike fit and upper body, it all seemed like everyone had their own opinion and seemed to depend on riding style and desired comfort. Some fit opinions agreed and others were way, way different. But, this bike fit calculator on competitivecyclist.com seems to have a complete calculator better than some bike shops pay to have at their store, if they have one at all. They go through the critical measurements and provide you with 3 different riding style fits for road biking, along with multiple fits for both mountain and triathlon biking. Keep in mind that these fits are for competition and are geared for more aggressive riding positions. So, if comfort is key, a higher and closer handlebar is usually the first thing to change to give you a more comfortable, more upright riding position.
Who knows if they’re right for you or for anyone else, but it will give you some perspective, when a bike shop fit specialist tries to sell you on a bike. This is not to say these bike fits are the only way to ride a bike. Especially when the best way to fit a bike is to actually ride one, but it should provide an excellent starting point to tweak from.