All models of bikes have a unique bike. Sizes from 16-inch to 24-inch are more common than others. But there are manufacturers who like to produce frames with polzuemoy step (for example, of 16.5). Many people think that the distance from the axis of the BB to tip of seat tube is the frame size. And in fact, it often goes like this option the different manufacturers. For example, 18-inch frame one manufacturer may not be identical to the 18-inch frame from another plant.
When you purchase or intend to purchase a Bicycle, be sure to measure the distance from the groin to the top of the pipe. Let it be not less than 8-10cm. For it is made to in the case of a sharp brake and a simultaneous jump of the bike you didn't get hurt. If you're not going to scorch, and will ride quietly, can this recommendation be disregarded. But still to buy a bike with the aforesaid distance is less than 5cm is not recommended to anyone.
On the model that you like, pay attention to fit. The fit should be as comfortable as possible. You do not want ever to be tired and drive at low speed? And that's the main drawback of mismatched landing.
Carefully examine the saddle. Adjust it the right height so that your leg while driving, causing the pedal in the lowest position, straightened fully. If not rectified, it is necessary to purchase a larger size saddle.
Make sure that the drive you safely and effortlessly reach the wheel. Suppose you do not want even a little move back or bend forward even more. Otherwise, then can start back pain due to unhealthy situation.
Let's say you want to order a bike via the Internet. No need to hurry. It is better to first go to a regular store, find your favorite model. Follow all the recommendations given above. Ride on this bike and only then order. Otherwise it may happen that the purchased model does not suit you and instead of enjoyment have to suffer the hurt and discomfort.