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How to Measure a Road Bike Frame

how to measure a road bike frame

When buying a new bike or renting one, you need to know the right size of the bike frame for you to get the right fit. But how to measure a road bike frame? This article will show you the step-by-step process of measuring the frame of a road bike.

What You Will Need:

  • Tape measure
  • Clinometer – for measuring angles (An app that can be downloaded through your smartphone)
  • Long spirit level
  • Plumb line

Step 1: Measuring the Top Tube Length

The top tube length, also known as the effective top tube length or the virtual top tube, is actually the horizontal distance from the centerline of the head tube to the centerline of the bike’s seat post.

Measuring it correctly is very essential since this is an integral part of the bike frame. You can use the spirit level or the clinometer app to ensure that your measurement is horizontal and accurate.

Please note that most manufacturers usually base their sizes on measuring the top tube length. However, the brand’s interpretation for the size of the top tube length differs from one another. But measuring the top tube length first is the key to getting the right road bike frame size.

Step 2: Measuring the Reach and the Stack

Yes, measuring the top tube length is fine, but measuring the reach and stack is also needed to get more consistent. In this step, you will need to measure the top of the head tube and the bottom bracket. Again, you will need to use the spirit level to get an accurate measurement.

During the measurement, you will need to attach the plumb line to the end part of the level. But you need to make sure that the blob is symmetrical while the string should hang down straight. Then, you can align the top edge of the level with the centerline on the top portion of the head tube.

Then, start moving the level back and forward so that the plumb intersect in the middle of the spindle of the bottom bracket. After that, just measure the distance from the top of the plumb line and the head tube to get the reach measurement.

Meanwhile, when measuring the stack, you need to measure the distance between the bottom bracket and the top of the head tube. So, once you have the reach measurement, you can easily measure the stack using the plumb line.

measuring the reach and the stack

Step 3: Measuring the Wheelbase

Measuring the wheelbase is also essential as it varies depending on the bike frame type. The wheelbase is the distance from the front axle to the bike’s rear axle. But during measurement, you will need to straighten up the bike fork to get the accurate measurement.

It will be better if you keep repeating the measurement to ensure that you will have accurate data. You can also try to measure both sides of the bike so that you can compare the measurement and select the most accurate one.

Step 4: Measuring the Front Center

The front center is also a component of the wheelbase which is the distance from the axle to the front dropout. Measuring it accurately is essential as it also affects the bike handling of your bike and the top overlap as well.

Step 5: Measuring the Chainstay Length

Another essential component of the wheelbase is the chainstay length. The chainstay length is actually the distance from the center of the bottom bracket axle to the bottom of the rear dropout. Measuring it is essential as this component also affects handling.

Usually, a shorter chainstay is livelier compared to those that are longer. When measuring, a ruler will be used to get the accurate distance.

Step 6: Measuring the Bottom Bracket Drop

When finding the right bike frame size, the bottom bracket drop is another key measurement set by most bike brands. It is actually the difference between the height of the wheel axles and the crank axle’s centerline.

When measuring the bottom bracket drop, you will need to measure the height of the rear axle and the height of the bottom bracket. Then, you can get the difference between the two measurements to get the bottom bracket drop.

Step 7: Measuring Bottom Bracket Height

Another important data to get when measuring your road bike frame. The height is easier to get since it is the distance from the ground to the center of the bottom bracket shell.
But before measuring the bottom bracket height, you will need to get the bike straight for you to have an accurate measurement. You will also need to inflate the tire to its usual running pressure for accuracy as well.

Step 8: Measuring Seat Tube and Head Tube Angles

Measuring the angles of the head tube and the seat tube is also essential as it affects the handling of your bike. Usually, a more upright tube angle will provide the biker with a more agile bike handling.

You can measure the angles of the head tube and the seat tube using the clinometer app of your smartphone. Meanwhile, if your bike comes with a straight seat tube, all you have to do is line up your smartphone to get the measurement through the app. But make sure that your bike is standing on a horizontal surface to get an accurate measurement.

Conclusion

Learning how to measure a road bike frame is essential when you are going to get a new bike. Many parts of the bike frame need a measurement for you to be able to size up your preferred bike frame size. Once you have these measurements, keep the records in a safe place and always refer to them if you need to size up a new bike frame for your bike.

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