How to Select the Correct Bicycle Frame Size

Bike frames left the concept of "one-size-fits-all" long ago. Modern bike frame have many configurations. Some graduate in inches, some in millimeters. Some bike manufactures refer to their frames as "small", "medium" and "large". Frame sizing takes account of the type of cycling you choose to engage in. You'd select tall frames for cruising and smaller frames for racing. Whatever frame size you choose should fall between a few recognized parameters.

Things You'll Need

  • Allen wrench 5 mm
  • Allen wrench 4 mm
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Instructions

    • 1

      Measure your frame size by straddling the bike. Stand over it with your feet flat on the floor. For a road bike you should have 1 to 2 inches of clearance between your crotch and the top tube. For a mountain bike 1 to 4 inches is acceptable.

    • 2

      Sit down on the bike to adjust the seat height. Put one foot on a pedal and extend your leg to the bottom of the pedal stroke. Your leg should be almost fully extended with a slight, 5 degree, bend in your knee. Raise or lower the seat, using an Allen wrench to loosen the seat post, until you complete the adjustment.

    • 3

      Check the distance from the bottom of the seat to the point where the seat post enters the bike's frame. If the seat is bottomed out or within 1/2 inch of the top of the bike frame, the frame is too tall.

    • 4

      Check the seat post. If you can see height limitation marks on the seat post above the point where the seat post leaves the bike frame, the frame is too small. The limitation marks will be a circle or serrated marks, or both, cut into the seat post. If you can place your feet on the ground while you are sitting on the seat, this is also indicates your frame is too small.

    • 5

      Kneel down at eye level with the bike and sight across it sideways after first adjusting the seat height. If you are more concerned about comfort, your frame size will require that the handlebars are slightly higher than your seat. This frame size is more suited for the cruiser or mountain bike.

    • 6

      Check the handlebar frame height for road bikes. After first adjusting the seat, get at eye level and sight across the bike. The handlebar height should be even with the seat, or slightly below it. This frame size makes the bike more aerodynamic, faster and more aggressive.