How to Pick a BMX Frame Size

Written by kochava r. greene
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How to Pick a BMX Frame Size
BMX bikes are built to be small and to allow the rider freedom of motion. (bmx image by claude wolf from

BMX bikes come in several sizes, usually paired with the age of the rider. Because the bikes are designed for tight corners and tricks, they often are smaller than a road or mountain bike would be when fitted for the same person. Most BMX bikes are outfitted with 20-inch wheels, upright handlebars and small seats.

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    Go to your local bike store and try on some bikes. What you're looking for is called "standover height," the distance between your body and the bar (called the top tube) of the bike. You want 2 to 4 inches between the top tube and your body. In general, children ages 4 to 6 years will fit on mini-size frames; those 6 to 9 years old on junior size; 9 to 13 years old on expert size, and youths over 12 years of age on pro size. These are just guidelines, and you may find that you prefer a size up or down.

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    You also can size a BMX bike by using a longer or shorter top tube. Many bike shops will customise bikes by installing a tube that fits your size more closely. This is done when you feel that the distance between the seat and the handlebars is too short or too long. Top tubes on the majority of BMX bikes are 20 inches, but you can also have top tubes that are 18, 18.5, 19, 19.5, 20.5, 21 and 21.5 inches. When you sit on the bike's seat, rotate the front wheel using the handlebars as you will when you ride. If you are straining to reach on the outermost rotations, you may want to have a smaller tube installed to put you closer to the bars. Similarly, if you feel cramped a longer tube may work. The correct top-tube length will depend on your height and arm length: Try several test bikes in the shop to see what feels most comfortable for you.

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    Adjust the seat and handlebar heights to get an idea of how riding, racing or doing tricks will feel on a selected bike. If you feel too cramped, try going up a size. Likewise, if there's too much air between you and the bike, you may want to move down a size.

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    Take the bike for a test ride. If you feel like you're between sizes, ride them both and adjust the seats and handlebars as you go to see which feels most comfortable. Most bike shops will let you try out BMX bikes in the car park or in special tryout areas next to the shop. Ask the shop's bike fitter to watch you ride and make recommendations based on what she sees.

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