Stems

Stems

Sorting

Put simply, stems connect the handlebar to the bicycle. The stems you will find at the co-op will generally be quill stems, like the one in the picture below. The lower part jams into the bicycle frame and the circular hole clamps around the handlebar. Quill stems can vary in three ways, and will generally vary in two ways at the co-op.

Quill Size

7/8" Stem

One way is the size of the quill - the lower part of the stem can be three different sizes, to fit different types of bicycles. 7/8" stems and 1" stems look similar. As the names indicate, 7/8" stems are slightly smaller than 1" stems. But don't use calipers to measure, because neither one is the size it says, and you will only be confused. You can tell the difference by trying to push the stem into the tube on the stem cabinet labeled "7/8" sizer", pictured to the right. A 7/8" stem will fit, and a 1" stem will not. 1 1/8" (one and one eighth inch) stems are plainly visibly larger.

Length

The second way is the length of the quill and length of the extension (the part of the stem that goes forward to hold the handlebar). At the co-op, we sort stems by the length of the extension, ignoring the length of the quill. The drawers are either sorted by length in millimeters or sometimes by "short" vs. "long". Like with saddles, stem extension lengths are best sorted by comparison to things already in the drawer. In the picture below, the length of the extension is the distance between the two red dots; it is measured "center-to-center".

Clamp diameter

Quill Stem Parts - The wedge bolt head is visible from the top of the stem, just under where it is labeled.

The third way in which quill stems vary is not one that you will generally encounter at the co-op, but you should know about it. The area where the stem clamps the handlebar can be sized differently. On modern bicycles, "road" handlebars are almost always a slightly larger size than "flat" or "mountain" handlebars, and there is a third size which is even larger that is sometimes used for either type on very expensive bicycles. Almost all stems and handlebars at the co-op are of the smallest of the three sizes, which is 25.4mm, or exactly one inch.

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