Buying a bike isn’t a complicated process. However, if you plan to have one of the mountain bikes, you must make sure that it fits you. While purchasing a bike, stay reminded of the preferred type of riding. Also, for full-suspension mountain bikes, measuring is essential because it determines your bike’s handling.
Therefore, this article brings you a complete measurement guide for your bike frame. Whether you need a road bike or full-suspension mountain bike, measuring the frame is essential to guarantee its usefulness. The guide also focusses on the perfect size frame for road bikes, and the best mountain bikes.
Tools to measure a bike frame
Before buying the mountain bikes or road bikes, measure their frame using a tape measure, clinometer, long spirit level, and a plumb line. A clinometer measures angles. It is also available as a free smartphone app. In place of the long spirit level, you can also use the clinometer app with a straight wooden piece.
Measuring bike frames
Given below are measurement methods for top tube length, seat tube length, wheelbase, chainstay length, front center, seat tube and head tube angles, bottom bracket drop, and bottom bracket height for the mountain bikes (including full-suspension mountain bikes) and road bikes.
Top tube length
For a consistent measure of the mountain bikes, regardless of the top tube angle, you need to measure the horizontal top tube length, termed the sufficient top tube length or virtual top tube in many geo charts. It is the horizontal distance between the centerline of the head tube and the centerline of the seat post. Mapping it will mean using your spirit level or the clinometer app, to guarantee that your measure is especially horizontal. Many manufacturers size full-suspension mountain bikes and road bikes by top tube length.
Seat tube length
Seat tube length for full-suspension mountain bikes is the straight line distance between the center of the bottom bracket and the top of the seat tube. Full-suspension mountain bikes, in particular, often have a curve in the seat tube. It would be if you lined up your straight edge with the bottom bracket center and the top of the seat tube and measure along with this. It will make the measurement for the mountain bikes easier for you.
Wheelbase
For the mountain bikes, the frames’ wheelbase is the distance between the front and rear axles. It’s an essential determinant of a frame’s ride quality and will vary with frame size. It’s reasonably easy to measure, although you need to set the fork straight ahead, or your measurement will be wrong.
Accuracy will also be enhanced if you measure the wheelbase on both sides of the bike and take the aggregate. So, in full-suspension mountain bikes, it will compensate if the fork is not straight.
Chainstay length
Chainstay length for full-suspension mountain bikes is one of the two components that make up your wheelbase and majorly contributes to your frame’s handling characteristics. The mountain bikes‘ frame with shorter chainstays will naturally feel livelier than one where the stays are longer. The chainstay length is the straight line distance between the center of the bottom bracket axle and the center of the rear dropout. It is, therefore, effortless to measure with a ruler.
Front center
The other component of the wheelbase for the mountain bikes is the front center. It is the equivalent of the chainstay length but estimated from the axle to the front dropout. It affects handling and toe-overlap with the front wheel. Full-suspension mountain bike makers do not often quote this front center. Remember that the wheelbase is not the sum of the chainstay length and the front center because neither of the two is marked horizontally.
Seat tube and head tube angles
For full-suspension mountain bikes, the seat tube and head tube angles are two of the most significant factors for determining to handle, with more upright tube angles typically leading to more agile handling. Use the clinometer app. If you’ve got a straight seat tube, you can estimate the seat tube angle by lining up your smartphone and reading the number from the clinometer app. Keep your bike vertical and stand on a horizontal surface for an accurate reading.
You can get close to the center line’s angle by holding your phone at the angle of the centerline or using a straight edge to line up with the centers of the top and bottom of the head tube. If you have upright fork legs, without an angle at their crown, the legs’ angle will be identical to the head tube angle so that you can measure this instead. It’s necessary to have the bike standing vertically for the mountain bikes or road bikes. You can also estimate the head tube angle by lining up the clinometer with the steerer extension over the head tube.
Bottom bracket drop
The bottom bracket drop is the difference between the height of the wheel axles and the centerline of the crank axle of the mountain bikes or road bikes. You can measure it by determining the height of the rear axle and the height of the bottom bracket. After that, you need to subtract one from the other. It’s another essential measurement quoted by famous full-suspension mountain bike brands on their charts.
Bottom bracket height
The bottom bracket height for the mountain bikes or road bikes is from the ground to the center of the bottom bracket shell. It is quite easy to measure, although it is crucial to be careful to keep your full-suspension mountain bike straight upright for an accurate reading. Unlike the bottom bracket drop, it will be affected by the tires too. Make sure to inflate them to your normal running pressure.
How To Measure Full-Suspension Mountain Bikes?
Full-suspension Mountain bikes are a unique class of mountain bikes, equipped with front and rear suspension. Each manufacturer has its design for handling the rear suspension, but they all assist the same purpose of allowing the rear tire to move up and down and absorb shock from uneven terrain. The frame size is concluded by the length of the seat tube, even if it isn’t a straight, continuous tube. The instructions following explain how to measure a full-suspension mountain bike.
Firstly, identify the top of the seat tube, where the seat clamp grips the seat post. Secondly, identify the center of the bottom bracket. It is the axle that retains the crank arms together. After that, measure the distance between the two points. You will get the length of the seat tube. Make sure to record your measurement in both centimeters and inches. Finally, after measuring your full-suspension mountain bike size, check the height-chart to know if it is one of the mountain bikes.
How to measure traditional mountain bikes?
Traditional mountain bikes, those without suspension, are prevalent among older used bikes. Made of steel or aluminum, accommodate knobby 26″ tires and holding flat handlebars with a trigger or grip-type gear shifters, the seat tube’s length concludes the frame size of the mountain bikes. The instructions below describe how to measure a traditional mountain bike.
To measure the mountain bikes (traditional), identify the top of the seat tube, where the seat clamp secures the seat post. Secondly, identify the center of the bottom bracket. Thirdly, measure the distance between the two points. It is the length of the seat tube. After that, record your measurement in both centimeters and inches. Lastly, check your bike size with the height chart and buy the mountain bike for yourself.
How to measure hardtail mountain bikes?
Today, most mountain bikes are hardtails, indicating they have suspension in the front, not in the rear. This style is popular among mid-level and high-end bikes. They are typically made from steel, aluminum, or carbon fiber, and possess flat handlebars with a trigger or grip-type shifters. The length of the seat tube decides the frame size. The instructions below demonstrate how to measure a hardtail mountain bike.
To measure the mountain bikes (hardtail), first of all, you need to identify the top of the seat tube, where the seat clamp grips the seat post. Then, try to identify the center of the bottom bracket (it’s the axle that holds the crank arms together). After that, you need to measure the distance between the two points. After that, record your measurement in both centimeters and inches. Finally, you can select your bike by comparing the obtained measurement according to the height chart.
Conclusion
This article gives the tools and techniques to measure various parts of a road bike or the mountain bikes (especially full-suspension mountain bikes) including top tube length, seat tube length, wheelbase, chainstay length, front center, seat tube and head tube angles, bottom bracket drop, and bottom bracket height. It also focuses on measuring hardtail and traditional mountain bikes. Measure the size of bike frame, use the height-chart, and buy the bike for yourself.
