Quills, Goose Necks, Threadless: Bicycle Parts or Animal Anatomy?

English: Taken by Andrew Dressel
Taken by Andrew Dressel (Photo credit: Wikipedia)
English: Taken by Andrew Dressel
Taken by Andrew Dressel (Photo credit: Wikipedia)

The stem, if you recall, is the part that connects your handlebars to the fork via the fork steerer. Don’t worry about not knowing what the fork steerer is, we’ll hit that up in a later post about the fork. Anyway, there are two kinds of stems. For the most part. There are some wacky ones out there, but we’ll concentrate on the two most common kinds: the quill stem, and the threadless stem. To make it easier, I’m going to use a picture, then explain it from there.

Okay, check it. The stem on the top is a quill stem, and the stem on the bottom is a threadless. You’re probably now to the point where you are asking yourself “And I need to know this why?” I’ll tell you why, even if you aren’t asking yourself that question. The stems are incompatible with each other. There are some fancy adapters, but I’ll discuss that later. Just know that one stem style does not fit on the other.

Quill Stems

Bicycle stem
Bicycle stem (Photo credit: Wikipedia)

Quill stems were the standard when bicycles were invented. They are inserted into the fork steerer and a bolt is tightened to pull a wedge up that tightens the stem in place. Refer to this picture. The bolt you tighten is hidden but you can clearly see the wedge at the bottom. As it is pulled up by tightening what is called the stem bolt, it wedges it self in the steerer tube thereby connecting the stem to the fork. Now we’re steering! The handlebar slides through the loop up top and another bolt is tightened to clamp it into place. This stem is still in use today. If it ain’t broke, don’t fix it, right? Well, technology marches ever forward when it comes to bicycles.

Threadless Stems

Ahead bicycle stem
Ahead bicycle stem (Photo credit: Wikipedia)
Enter the threadless stem. I remember when it was call the Aheadset Stem. I just aged myself. This was because a company that manufacture the Aheadset brand headset came up with this nifty system that saved weight and provided a more direct connection to the fork. I mean look, even the picture from Wikipedia is captioned “Ahead” bicycle stem.
As you can see, this stem is more minimalist. It works by clamping around the steerer tube as opposed to wedging itself internally like the quill stem. The bolts on the left are what clamp the stem around the steerer tube, and the handlebars are clamped in the opposite end. Safety Note: You can swap the ends around. I dd it as a joke once, but the stems are not designed for that. This stem was lighter, and most riders felt, more responsive than the quill stem.


Now you need to know how to measure these dang things. First thing you need to know is the steer tube diameter. For quill stems, they are either 1″ or 1 1/8″. There is an older size that’s found on old Schwinns and such, but we’re sticking to modern bicycles (remember the first post?). Threadless stems come in either 1″, 1 1/8″, or 1 1/4″. The 1″ and 1 1/4″ aren’t all that common and tend to be on either specialty bikes like time-trial bikes, and/or mountain bikes from certain manufacturers. Want to know how to know to figure out what size you have? If you have a set of dial calipers handy (or digital if you’re fancy), you can measure the inside diameter of the steer tube for quill stems, or the outside diameter of the steer tube for threadless. A steer tube measurement of 22.2mm is 1″, and a measurement of 25.4mm is 1 1/8″. You’re probably thinking, “Hey, those don’t convert to 1″ or 1 1/8″. Plus guys in really tight jeans look odd.” To answer the first thought, you are measuring the inside since quill stems are inserted. You could measure the outside, but usually the steer tube is covered by the headset, and this is a quick way to measure without having to remove any headset parts. We’ll cover the headset later. As for the second thought, it’s all subjective. Steer tubes for the threadless stem will measure out to the different sizes without any weird conversions.

Another set of measurements are the length and rise on the stem. Length is pretty self-explanatory. For a quill stem, you have two, count them two (2) lengths to consider: the quill length, which is the part inserted into the steer tube, and the stem length itself, which is measure from the center of the stem bolt to about the center of where the handlebars are. This is usually the standard way of measuring them, though some companies fudge that. Threadless stem length is measured the same way. The rise is the angle of the stem relative to a horizontal level. For a quill stem, that would be where the quill is vertical. On a threadless stem, you have to have an imaginary vertical line running through the part that clamps around the steer tube. Rise is expressed in degrees from that horizontal. For example: 6 degree rise, the stem rises upward at a 6 degree angle; -6 degree rise, the stem drops at a negative 6 degree angle. The higher the amount of degrees, the steeper and higher the stem rises. We’ll discuss the effect of this when I post the article about fitting.

So there you have it. Stems in a nutshell, or something. This is all heady stuff, so if you have to take a breather, that’s okay. If you have any questions, that’s okay too. Feel free to fire off an email at me. I try to respond within 48 hours. Depends on how my zombie-fighting class goes.

Keep riding!


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