IN THIS GUIDE OUR MOST EXPERIENCED SHAMAN - RONALD - WILL GUIDE YOU THROUGH PROCESS OF CHOOSING THE RIGHT SIZE OF BIKE FOR YOU.
Just like the clothes you wear, bicycles are available in a range of sizes to suit different bodies. Height- as in how tall you are, is the primary factor which determines which size bike will suit you best.
I am going to attempt to compose a simple, universal sizing guide here. This is difficult, as different manufacturers express their size range in different ways. Some models come in as few as two different sizes, some as many as six. Size can be expressed either as a size range in terms of “small- medium- large”, just like the t-shirts you buy, adding “ extra....” or even” extra, extra.....” to either end of the scale to cover a range of up to six sizes.
The other way is a measurement of the seat tube (the part of the frame, that the post that holds the saddle is inserted into) generally expressed in centimeters, measured from the center of the bottom bracket (the short tube down the bottom of the bike that the cranks are fitted to) to the top of the aforementioned seat tube, where the clamp that holds the post is found. This can be from 48 cm, at the very smallest- which could also be called “extra small”, right up to 62 cm at the very largest end of the scale, which would be an “extra large” or even an “extra, extra large”.
Some manufacturers give both. For example: the Fabricbike Original (a simple singlespeed “fixie” type bike) comes in three sizes -”small”=49 cm, “medium”=53 cm and “large”=58 cm. Though, really, it doesn't matter. This centimeter measurement would only be reliable for our purposes if all frames were laid out the same and measured in the same way . Which they aren't. The thing that is universal is that a “small” size bike is for a “small” size person, “medium “ for “medium” people and so on.
Production, adult bicycles are generally sized to cater for a range of rider heights from approximately 148- 150 cm up to over 200 cm. If there are five sizes available, break that range into five equal parts, then determine which part your height best fits into. For three available sizes, break the range into three equal parts. And so on. I have made a graphic which I hope will make this principle clear.
Notice that there is a fair amount of overlap with the sizing. If your height places you around the border between two sizes, it helps to know how your own body is proportioned. Generally, it is safer to lean towards the smaller size- unless you have long legs with a short torso- in which case bigger is probably better. However, you won't die if you are on the border between two sizes, no matter which one you choose. During my messenger years, I rode whatever I could lay my hands on, within a certain range. Frequently a bit on the small side, a couple a bit large, one conspicuously so. All could be classified as “large-extra large”.
At most suburban bike shops, this is all they try to do- determine where your height puts you within the available range of sizes. Hopefully I have provided enough information here to help you work it out for yourself, at this level. There are, of course, highly professional, highly specialized race shops offering very detailed bike fittings indeed- where they measure every part of your body in great detail, or use a special “size cycle”- adjustable in every dimension to come up with recommended measurements for every part of the bicycle down to the last millimeter. This is a service we cannot provide online. But unless you are looking to compete at the highest level, this is probably overkill anyway. In fact, in all my life I have never had such a fitting done. If you are honest about your actual height- guys- don't exaggerate- I am confident that you should be able to use this guide and graphic to get a bicycle in a size that will work for you!!