There are many methods, tricks and formulas for choosing a bike frame size. The frame size refers to the length of the seat tube, which can be measured center-to-center or center-to-top, resulting in even more confusion. Using a few different bike frame sizing methods will give you the most accurate numbers. However, the ultimate method for choosing a bike frame is to simply test out the bike. Ride several models and sizes, and choose the one that feels the best.
Step 1
Measure your inseam. The LeMond formula uses the inseam measurement to calculate the appropriate bike frame size. Remove your shoes and stand with your back against a wall. Place your feet about 6 inches apart. Place a hardcover book between your legs with the spine facing up. Press the edge of the book against the wall. Slide the book up firmly into your crotch. This simulates the bike seat. Have a friend measure from the spine of the book to the floor. For the most accurate number, measure three times and take the average as your inseam length. Take the measurements in centimeters.
Step 2
Calculate your center-to-top bike frame size by multiplying your inseam length by .67. This measures from the center of the bottom bracket to the top of the seat tube. Multiply your inseam length by .65 to calculate your center-to-center bike frame size. This measures the seat tube from the center of the bottom bracket to the center of the top tube. All measurements should be in centimeters.
Step 3
Use this initial bike frame size as a starting point. The LeMond formula calculates bike frame size for road bikes and it is not perfect. It can result in a frame size too small for taller riders. For a mountain bike, subtract 10 to 12 cm from the road bike frame size.
Step 4
Use the standover test to refine your choices. Go to a bike store and pick out a couple of possibilities. Stand over the bike, straddling the tube. For road bikes, you want about 1 inch clearance between you and the bike tube. Lift the bike. The clearance between the ground and the tires should be about 1 inch. If the bike has a sloping tube, shoot for 2 inches of clearance. For mountain bikes, you want about 2 inches clearance between you and the bike.
Tips and Warnings
- Test out the bike. This is the best method for determining if it is the right frame size.
Things You'll Need
- Tape measure
Member Comments