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| My Crude Frame Diagram |
Is it easy to mount?
Is it comfortable to stand in while at rest?
Is the reach to the handlebars comfortable, stretched or too compacted?
How does it feel to ride? Do your knees over extend or straighten out?
Do your feet have to "tip toe" to the pedals?
No matter what standard of measuring is used the exceptions abound. Each person is physically different in many ways and each difference matters to the overall fit. Long legs with a short torso but = 5' 7", will not fit the same bike as well as a 5'7"=long arms, average torso, long legs person.
With myself, and my kids, we fit a bike very simply. Ride it. Go over every action you would expect to use it for and have someone else who knows your purpose for doing this watch. This way you are not distracted from, simply riding the bicycle, by trying to analyze your every movement. Riding relaxed lets your body find it's most natural position. Your observer can then tell you how your feet may have been pointed the whole time, or how you rode on the tip of the seat or at the back edge. While riding you may not have even noticed these things even if looking for them. After a while, you can start to tell what aspects of certain frames work best for you. Most fitting issues are adjustable on most bikes. The seat can move up or down, front to back, or tilt. Handlebars can rotate forward or back, or raise up or down a little.
Despite all the ways to measure up for a bicycle, having a ballpark idea from any of these methods is not a bad thing, just not the last step before actually buying one. Some Bicycle shops fit a bicycle much more thoroughly, at your expense. Do not get me wrong, this is the ultimate in fitting a ride, but it is similar to building a bike from the ground up around you. Swap the crank arms longer or shorter, seat post, handlebar stem, and handlebars. It truly is a custom fit, but even this thorough method can leave you with a bike that is uncomfortable to ride. Some shops do not charge for this, as they are exchanging components, and some manufacturers supply extras for this purpose. These however are usually high end bicycles. It has to be worth their time and effort in doing all this work to fit you to the bike into their profit from the sale. Most of the shops that I have visited that do this use it as a last straw in the sale. If they can get you into a bike off the rack and have you willing to ride it home without alteration, even better. Don't blame them, you are the customer, so it is your job to push for those extra perks, they won't hand them out. This however only covers a narrow option available with fitting. You can also swap out these parts yourself later, but it is expensive and time consuming for the average cyclist.
If you have a bike that fits well and rides comfortably, measure it. Make note of the kind of bike as well. Your road bike may measure differently than a cruiser. At least having a starting point will narrow down your effort. Having these measurements can also help when you find an old fixer upper. Flat tires, broken seat or bent handlebars make it hard to check for a fit. If it is similar in design to one that you know fits, check the measurements.
Top tube length, seat tube length, and stand over.
Stand over is an old rule of having two inches below your crotch to the top tube when you stand over the frame. While this is not the best overall way to fit a bicycle, it is a good judge of range. If the top tube is near your belly button when you stand by it, try again. This rule mostly applies to road and some mountain frames. Some lower cruisers, lowriders, BMX, limo's and so forth are lower by design. In the End, ride it. Comfort is key. Nobody likes to see someone with their backside jacked up over their shoulders riding down the road straining to reach the pedals. It isn't fun either, and can ruin any possible enjoyment you can get from riding a bike.
If you are building a bicycle from the frame on up, I imagine that you have some idea of size, if not go find similar frames to your planned build and try them out before you buy your frame and parts. For a beginner with the itch to start from scratch, seeing a similar complete bike can also focus your ideas, choose better components, and imagine the end result. Sizing up a bike after all isn't only for whether it fits or not.
With all of the information out there and opinions on how best to apply geometry and calculus, remember that buying a bike should be as relaxed and fun as riding one.
