Bicycle fit and sizing
Bike sizing is surprisingly complicated. Our philosophy at the shop is that you're the ultimate bike fitter for yourself, because only you will understand how your body feels on your bike. As we age, as our riding styles change, and as we become ever more competent riders, we may prefer different qualities in our bicycles over time. Here, we won't delve in too deep: this is some general information about getting started on a bike that's the right size for you.
Although many bicycle size guides will tie certain bike sizes to certain heights, height is just a ballpark way to guess what size someone should consider. Bike fit has much more to do with your inseam and the length of your arms.
Imagine someone straddling a classic 'diamond frame' (not a step-through) bicycle—not sitting in the seat, but ahead of it, "standing over" the bike. The top of the bike should be one or two inches lower than their crotch. Not only is this much more comfortable than the alternative (bike up in your business), it also makes the bike easier to mount, dismount, and control.
At home, you can measure your standover height with a tape measure, a book, and another person. Wear shoes similar to what you'd ride your bike in. Stand against the wall, cram the spine of the book between your legs, and hold the end of the tape measure on top of the spine. Have someone read where the tape measure hits the floor. Now, if the bike you're considering has 'standover' listed in the specs, you can look for whatever size matches your standover height minus one to two inches.
Reach—the distance between your butt and your handlebars—is easier to dial in once you've found a bike that's the right height for you. Handlebars, stems, and saddles can all be adjusted or swapped to increase or decrease the distance you reach forward. However, some people with very long legs and relatively short arms—or vice versa—will search out bicycles that have a shorter or longer top tube relative to the seat tube.
As you can see, even when we only consider the most basic factors of fit, there's a lot to take in. The easiest way to get an idea of how this works in practice is to ride some bicycles. If you've got a similarly sized friend with a bike, ask if you can try it out. Head to local bike shops and ask to try out a few bikes for size. Different models will have different geometry: some bicycles of the same size will have different riding and reach charateristics. Try out as many bikes as you can! The goal is to find one that feels good to you—something you feel comfortable, relaxed, and in control on. If you're feeling wobbly, don't hesitate to lower the seat so you can comfortably put your feet on the ground. You can raise it later on when you're more familiar with the ride.
It's easier to ride a bike that's a bit too small than a bit too big, so when in doubt, size down. Step-through bicycles (which you may also know as a Dutch bicycle, a woman's bicycle, or a mixte) can be more forgiving for shorter riders since the top tube is out of the way and the reach towards the handlebars tends to be shorter.
We've barely scratched the surface of bike fit, so come by the shop anytime if you'd like to discuss further.