The stem is the part of the bike that joins the handlebars to the frame through the fork’s steerer tube. The stem allows you to control the height of the handlebars, meaning that changing the stem will affect the posture of the body. In general, stems are usually made of carbon or aluminium alloys.
There are two types of stems, defined by the union with the frame: quill stems and threadless (or ahead system). Quill stems are found in the oldest bicycle models. Stems of this kind insert into the fork’s steering tube. They are also known as threaded stems because in the upper part they have a bolt that, when tightened, pulls the wedge against the stem to expand against the inside of the steerer tube and hold the stem in place
Threadless stems, on the other hand, are found on the newest bicycles. It is a cylindrical piece of about 10 cm that joins the handlebars with the fork and that can move on the vertical axis of the fork to be positioned for the cyclist’s size. When tightening the bolts of the stem, this clamps the fork tube in the middle, fixing the stem well.
Stem Rise and Length
When purchasing a stem, two essential parameters must be taken into account: rise and length. For mountain bikes, the standard measurements are between 0º and 5º inclination and 120-130 mm in length. Specific road bikes stems tend to be longer and thinner, with lengths ranging from 70 mm to 130 mm.
When determining the length of the stem, the cyclist’s flexibility must be taken into account. More flexible people should opt for longer stems, especially for mountain bikes. The rise or angle, on the other hand, influences the control of the bicycle. At a greater angle, the posture will be more upright and safer, more controlled descents can be achieved. When the tilt is smaller, the cyclist has a more reclined position, which helps cyclists on steep climbs.
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