The fundamental measurements representing your frame are crucial if you are planning to purchase a new bike or your debut bike, as you want to be sure you acquire a bike that suits you and functions well for the types of riding you expect to undertake. If you are renting a bike, knowing your frame’s necessary measurements can help ensure that your rental is pleasant to ride and can be altered to fit you. Because frame sizes are not uniformly measured between manufacturers, you must look at a few key metrics to make sure you are making the right comparison.

What You Will Require to Take Bike Frame Measurements

A ruler and a measuring tape

A tool for measuring angles called a clinometer (they are downloadable via your smartphone)

Use of Spirit level (alternatively a piece of wood used together with the clinometer application)

Using a Plumb line (alternatively use some Blu Tack blobs together with strings)

Some producers are still sizing mountain bikes according to inches, whether they are road or mountain bikes. Brands like Moots combine the two.

To avoid confusion, we strongly advise you to stick with metric measurements. If you must use centimeters instead of inches, you can do so by multiplying centimeters by 2.54.

Typically, a maker’s website will have a geometry chart showing all of the frameset’s sizes. Consider making a copy of the owner’s manual if your bike is still in good working order. It would be more precise than your standard measure data and will serve as a helpful guide in the future.

Seat Tube Length Measurement

To measure seat tube length, measure the distance from the lower bracket center to the seat tube peak linearly.

A bike much like Trek Madone has an extended seat tube over the upper tube joint, making this more complicated than it appears. On the other hand, several have a seat mast, making it difficult to match the two.

You do not want to ride a mountain bike with a kinked seat tube since the straight lines of the tube will be lengthier. If you are unsure, the lower bracket midpoint and the upper of the seat tube should be lined up and measured together with a straight edge.

Measuring the Stack and the Reach

The lengths of the seat tube and upper tube can be confusing when comparing frames, as we have seen. Therefore, almost all bike producers will list the reach and stack parameters they use on their bikes to ensure uniformity.

Since each frame is designed independently, and measurements are taken at two critical contact locations, these bikes have an advantage over others.

Reach is summarized as the length in between two points measured horizontally. Next, your spirit level will be required to carry out a measurement evaluation. Then, at the other levels’ end, run a plumb line. The blob at the end of your Blue Tack string should be symmetrical, and it should hang directly down; else, your measured values might turn out to be inaccurate.

Match the apex of the edge of the level with the midline of the head tube’s uppermost section. Next, back and forth with the level till the plumb line meets the middle of the lower bracket.

You may now calculate your reach by measuring the length between the upper end of the plumb line and the head tube. It is also possible to lean the bike upon a wall, evaluate how much your lower bracket and head tube extends, and then deduct those values. So long your measurement is straight, you are good to go.

In bicycle terms, the stack assesses how far the lower bracket extends up the head tube. Be capable of measuring your stack by considering the plumb line once created to register your reach.

Wheelbase Measurement

The range in the middle of the front and back axles is known as the wheelbase. It is an essential factor in determining the ride quality of a frame, and it will vary depending on the frame size.

It is relatively simple to measure, albeit you must ensure that the fork is pointed directly ahead for your measurement to be accurate.

Just as with stack and reach, it is essential to repeat the measurement numerous times to ensure you obtain the same result each time. It will also improve the authenticity of the measurement if you evaluate the wheelbase through either side of the bike then choose the average since it will account for the fact that the fork isn’t perfectly horizontal.

Measurement of the Length of the Chainstay

As with wheelbase, the length of your chainstays is one of two factors that determine how well your frame handles work. It also has a substantial impact on the overall handling attributes of your frame. Chainstays of shorter length will often produce a more dynamic feeling in a frame when compared to stays of greater length.

With a yardstick, you can quickly determine how long a chainstay is by measuring it along a horizontal line from the middle of the bottom bracket axle to the middle of the back dropout.

Front Center Measurement

The front center is one of the wheelbase components. It is similar to the chainstay length; however, the measurement is between the axle and the front dropout. The front wheel has a way of influencing how it is handled, resulting in the front wheel overlapping. As a result, the total sum of front center and chainstay length is not equivalent to the wheelbase. It is because they both don’t have a horizontal measurement.

Final Thoughts

When it comes to mountain bikes, there is a lot of basic information that needs to be covered, and one of them is the measurement of the frame size. Getting to know the measurement of your mountain bike frame size is a significant step to help you understand the right size of bike that’s best for your biking activities. It is why you must understand these key metrics that will help you to carry out your bike frame measurements successfully.


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