Every bicycle manufacturer measures size a little differently. Some measure in inches, some in centimeters, some just in small, medium, and large. Some brands measure in inches for some styles and centimeters for others, further confusing the matter.
This means that, in terms of finding a bike to fit you, the number or letter is fairly meaningless.
Find a size that fits you
What you’re looking for in terms of fit is, first, stand-over height. You want to be able to stand over the bike frame comfortably when flat-footed. This is in case you need to dismount in a hurry – you want to be able to do that without injury.
Next, you want to look at how the bike feels from in the saddle – do you have good extension on the pedals? Is it a comfortable reach to the handlebars? This is more customizable: you can move a seat up and down a fair amount, forward and back a little bit, and you can move handlebars forward or back by adjusting or replacing the stem. You don’t want to feel hunched over, cramped, or reaching. The preferred posture is with elbows comfortably bent and back straight.
What you’re looking for in terms of fit beyond that varies on the type of cycling you’re doing. For BMX and dirt-jumping, as one’s skill grows, one wants a smaller bike in relation to the body, because it makes it easier to manoeuvre the bike for more involved riding, like serious obstacles or tricks. For road riding, you’d want a slightly larger frame because the more stretched out you are the more aerodynamic and well-positioned for maximum speed.
A properly fitted bike will be more comfortable on long rides, and on many rides over time. It’ll also help you perform better. Once you’ve settled on a frame that fits you, we can help adjust the bike to fit you as well and as comfortably as possible, including stem and seat adjustments and cleat position for clipless pedals (if applicable). At Goldstream Bicycles, our bike fittings are free.