When measuring a bicycle stem, there are three key dimensions to consider: length, handlebar clamp diameter and steering column clamp diameter. These dimensions are also necessary to adjust the stem of the bicycle. Here's how to measure each of these dimensions:
1. Measure Stem Length
The stem length corresponds to the distance between the center of the clamping screw (at the steering column) and the center of the handlebars.
Steps:
Use a ruler or tape measure to measure the distance between these two points.
Stem length is generally expressed in millimeters, for example 80 mm, 100 mm or 120 mm.
2. Measure the Handlebar Clamp Diameter
The handlebar clamping diameter is the part of the stem that grips the handlebars. The most common diameters are 25.4mm and 31.8mm for modern bicycles, but there are also 35mm sizes for some mountain bike handlebars.
Steps:
Use a caliper to measure the internal diameter of the part of the stem that grips the handlebars.
If you don't have a caliper, measure the diameter of the handlebar where it attaches to the stem to get this value.
3. Measure the Steering Column Clamping Diameter
The steering column clamp diameter is the bottom part of the stem that attaches to the bicycle's steering column.
Steps:
Most modern bicycles have a steering column diameter of 1 1/8 inch (approximately 28.6 mm), but some older or specific bicycles may have different diameters (1 inch or 1 1/4 inch, for example ).
To check, use a caliper or directly measure the diameter of the steering column before choosing a compatible stem.
Summary of Important Measures :
1. Stem length:
Distance between the center of the steering column screw and the center of the handlebar mount.
2. Handlebar clamping diameter:
Diameter of the part of the stem that holds the handlebars (usually 25.4 mm, 31.8 mm or 35 mm).
3. Steering column clamping diameter:
Diameter of the part of the stem that attaches to the steering column (often 28.6 mm for 1 1/8 inch).
By carefully measuring these three elements, you will be able to choose a stem that is perfectly suited to your bike and your riding preferences.
To go further :
Adjust the stem of a bicycle
Why change a bicycle stem?
