How to Size a Time-Trial Frame

A time trial bike has an aerodynamic design for racing in triathlons or time trials. In a time trial, each cyclist begins to race at a different time and rides the course to achieve the fastest time. The differences between time trial bikes are the handlebars that jut out from the front of the bike so the rider is more aerodynamic. The back wheel may be solid to reduce wind resistance, and the frame will have a different shape for aerodynamics. Having a time trial bike that fits you well is important for comfort and speed.

Things You'll Need

  • Tape measure
  • Assistant
  • Pen or pencil
  • Paper
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Instructions

    • 1

      Stand on a hard surface in bare feet. Take the tape measure and measure from your pubic bone, straight down to the floor. Have your assistant hold the tape measure straight and write down the length in centimeters. This is your pubic-bone height.

    • 2

      Subtract 10 centimeters from your pubic height. This number is your saddle height. Saddle height is the height of the top of your bike seat.

    • 3

      Subtract 12 to 14 centimeters from your saddle height. This number is your frame-size range. For example, if your pubic bone height measured 76cm, subtracting 10cm gives you a saddle height of 66cm. Subtracting 12cm and 14cm gives you the range of frame sizes of 52cm to 54cm.

    • 4

      Go to a shop that specializes in time trial bikes. Tell them the range you calculated and let them suggest a few bikes within that range. Your personal comfort, level of flexibility and torso length are key factors that play into the final "tuning" of the frame size.

    • 5

      Test ride the bikes they select for you. Test on the road and in the store's bike trainer. Once you find the frame that feels most comfortable, the sales person can help you adjust the seat height and angle to get the best fit.