How to Measure a Road Bike Frame

Your comfort and safety depend upon a perfect bike frame fit.
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To get the most out of your road bike riding, the bicycle’s frame must fit you correctly. A bike’s frame size is equal to the length of its seat tube. While there are a couple of different ways that you can measure a road bike frame, the center-to-top, or C-T, measurement is the easiest to take. It is also the simplest method to calculate and convert to correspond to your height for a proper bike fit. The C-T measurement is the distance in centimeters from the center of the bike’s bottom bracket to the upper end of the top tube, or seat tube.

    Step 1

    Lay the road bike on its side if you’re more comfortable working with it that way. The bike’s position won’t affect your measurement. It won’t matter if the wheels haven’t been secured to the frame yet.

    Step 2

    Find the crank shaft, which is an axle that runs through the bottom bracket cylinder. This axle joins the pedals together. Hold the end of a flexible measuring tape on the center of the axle.

    Step 3

    Run the tape measure to the top of the vertical tube that holds the seat post in place. The seat post is adjustable and fits into the seat tube. Don’t include the saddle or post in your measurement since it isn’t part of the bike frame.

    Step 4

    Record this measurement. Convert it to centimeters, as road bikes are measured metrically. One inch equals 2.54 centimeters; multiply the number of inches by 2.54.

    Step 5

    Test ride a diverse selection of road bikes with the correct frame size. They’ll all feel different to you in action since everyone’s riding style and body type is individual.

    Things You'll Need

    • Flexible tape measure

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