How to Measure a Mountain Bike Frame: Clear and Simple Methods to Do It
New to mountain biking? You might think that the frame’s size and measurement are not that important, but you’re wrong.
Not because you can ride it comfortably doesn’t automatically mean the bike frame fits you.
If you wish to take this sport seriously, you have to understand the importance of your bike frame’s measurements.
When you do, finding a bike that fits your requirements won’t pose any problems.
If you want to know how to measure a mountain bike frame, we made a detailed explanation of how you can do it below.
Tools to Measure Frame Size Mountain Bike
Before you start learning how are mountain bikes measured, you need to prepare a few tools.
- Tape measure
- Long spirit level
- Plumb line
If you want a more accurate measurement, we recommend that you measure the frame in metric units.
You can always convert it to inches if you want, but it is better to use metric units because these are what most manufacturers use.
How to Measure a Mountain Bike Frame
A mountain bike frame can be divided into several parts, which means that you are not measuring just a single frame.
Instead, you need to measure all of these parts to get the exact measurement of the frame.
Here, we will identify these parts and help you learn how to measure mountain bike frame size.
1. Top Tube Length
In the past, bikes had horizontal top tubes. After multiple design modifications, modern versions now have a slope on the top tubes.
However, we won’t really be looking at the slope for measuring top tube length. Instead, we will only focus on horizontal measurement for consistency.
The length of the top tube is measured by using a spirit level or clinometer app.
The top tube runs from the centerline of the head tube located at the bike handle up to the centerline of the seat post.
This is the most commonly used method of measuring the top tube length, though some manufacturers measure it differently.
2. Seat Tube Length
The seat tube length is the distance between the top of the seat tube and the bottom bracket’s center.
Measuring the seat tube length is fairly easy to do if you are measuring a Hardtail mountain bike.
However, there are instances when the task becomes tricky, especially for bikes with a seat tube extension.
There are also models where there is a kink on the seat tube, which would make it harder for you to measure the exact length.
Don’t let any of these confuse you.
Simply start at the bottom bracket and line up the measuring tool until you reach the top of the seat tube.
3. Reach and Stack
If you already had a headache with the seat tube and top tube length, measuring the reach and stack will surely make your head turn.
The stack is the vertical distance between the top of the head tube and the bottom bracket.
On the other hand, the reach is the horizontal distance between the top head tube and the bottom bracket.
The best way to get the measurement is to have at least two people do it simultaneously.
One would measure the reach, and the other would measure the stack to get accurate results.
To get the correct frame size mountain bike measurement, you should never forget the wheelbase.
The wheelbase is equal to the measurement between the rear and front axles. This would help determine the ride quality of the frame.
Measuring the wheelbase is pretty straightforward because you only need to measure the distance between these two axles.
For this, we recommend that you use a tape measure and start measuring them horizontally.
Make sure that you do multiple measurements to ensure you are getting the same number.
5. Chainstay Length
Why do you have to measure the length of the chainstay?
The length of the chainstay can affect the handling characteristics of your mountain bike.
A bike frame with shorter chainstays will feel more lively compared to a bike with a longer one.
It is very easy to measure since you only need to get the distance between the center of the bottom bracket axle and the middle of the rear dropout.
6. Front Center
This is the other side of the frame where you need to measure the length between the bottom bracket axle and the front dropout.
Like the chainstay length, it will also have a significant effect on the handling and control of the mountain bike, so this is very important.
You have to remember that the sum of the front center and the chainstay length is not the same as the measurement of the wheelbase.
The measurement of the front center and chainstay are not horizontal, so you cannot take the measurement of the wheelbase from this.
7. Seat Tube and Head Tube Angles
The seat tube and head tube angles can determine the handling of the mountain bike.
If the angles are more upright, it means that the bike can offer nimbler handling.
Getting the measurement of the seat tube and head tube angles are not too hard.
For this, you are going to use the clinometer app. The app will help you get the measurement accurately.
8. Bottom Bracket Drop
The bottom bracket drop is the difference in height between the wheel axles and the center of the crank axle.
To find its measurement, let your bike stand in a vertical position and then measure the height of the bottom and rear axle from the ground.
Subtract the values, and you can get the measurement for the bottom bracket drop.
9. Bottom Bracket Height
The bottom bracket height is one of the easiest parts to measure.
You just need to let your bike stand in a vertical position and measure the height of the bottom bracket from the ground.
Important Considerations on Measuring the Bike Frame
Most of the mountain bikes right now have different designs.
The methods mentioned above on how to measure a mountain bike frame is only applicable to those with traditional frames.
Bikes with a different frame would require a different approach when it comes to the measurement.
The manufacturers may also have their own set of rules when measuring the bike, so relying solely on the measurements you’ve made of a particular bike model will not be enough.
If you want to make sure that you are making the right measurements, you need to find someone who can also do the measurements.
Both of you should measure the same bike and compare the values that you got.
Always remember that it is very hard to get the exact measurement of the frame.
If you plan to use these values to buy a mountain bike in the future, just use the measurements as a standard and find a mountain bike with measurements similar to that.
How to Measure Mountain Bike Frame Size
Knowing how are mountain bikes measured is not easy. You need to consider different factors to make sure that you are getting the correct numbers.
If you are not planning to go deeper into the world of mountain biking, learning how to measure bike frame size will not be much of a benefit for you.
On the contrary, if you really want to enter this type of activity and do it full time, knowing your bike’s measurements will allow you to understand how the specific parts operate and how it can affect your performance.
Once you have the correct measurements, finding a mountain bike that suits your height and overall build should be easy.
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