Mountain Bike Stems: How to Choose, Adjust, and Change Them
Mountain bike stems come in a variety of lengths, angles, and materials. The bicycle stem connects the handlebars to the steering tube of the fork. It helps determine the distance of your reach to the handlebars and your position on your mountain bike, which influences how your bicycle rides and handles on the trail.
Quill vs. Threadless Stem
There are 2 basic types of mountain bike stems. The type that fits your mountain bike depends upon what type of headset you have, which accommodates either a quill stem or threadless stem.
Traditionally, quill headsets, also called threaded headsets, were the standard on mountain bikes, but almost all newer mountain bikes now have threadless headsets.
You can tell if your mountain bike has a quill headset if the stem is sort of an L-shape and goes down into the steerer tube and you cannot see the steerer tube.
Quill stems come in either a 1" size or 1-1/8" size. They can be more difficult to find than threadless stems because most newer bikes have threadless headsets.
Find 1" Quill Stems
Find 1-1/8" Quill Stems
Threadless mountain bike headsets are much more common on newer mountain bikes so if you have bought your mountain bike in the last decade, you most likely have threadless headset.
You can tell if you have a threadless mountain bike headset if you can see the steerer tube extending out from the headset. In this case, the back of the mountain bike stem clamps around the steerer tube, usually with 2 bolts.
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Length of Mountain Bike Stem
Mountain bike stems come in many different lengths. The longer the stem, the more stretched out you are and the farther you are away from the handlebars.
Bicycle stems are measured in millimeters.
Threadless stem length is measured from the center of the steerer tube opening to the center of the handlebar opening.
Quill stem length is measured along the part of the stem that goes to the handlebars. Length is measured from the center of the part of the stem that goes up (right where the top bolt would go through it) to the center of the handlebar clamp.
Cross country mountain bikers often tend to prefer longer stems, around 80-120mm, because this places the rider further forward on the bicycle, which is better for climbing.
For downhill mountain biking, shorter stems are often preferred because this places the rider further back on the bicycle and provides more stability for downhill riding.
Angle or Rise
The angle of a bicycle stem refers to how much it rises up from the steerer tube or, in other words, the height it places the handlebars. Angled threadless stems can be flipped over to drop your handlebars. Some quill stems are adjustable, but most come as one piece and have a fixed angle.
Stem rise is measured in degrees. Mountain bikers who do more climbing usually prefer less rise in their stem, like around 0-10 degrees. For downhill mountain biking, a little more rise, like 10-15 degrees is often preferred in order to bring the handlebars up closer and add more stability.
Adjusting Mountain Bike Stems
The height of both threaded and quill mountain bike stems can be adjusted to help customize the fit of your mountain bike.
Adjust Threadless Headset Height
If you have a threadless headset and you want to raise or lower your bike stem, you can move the spacers that are located above or below the stem.
In order to move the spacers, unscrew the bolt that is on top of the steerer tube. Then loosen the 2 small bolts that attach the mountain bike stem to the steerer tube. Pull the stem and handlebars off the headset being careful not to pull or bend the cables. Add or remove spacers below the stem so handlebars are at the desired height. Slide the bike stem back on the steerer tube. Tighten the top bolt before tightening the small bolts.
Adjust Quill Headset Height
To change height of a quill stem, loosen the stem anchor bolt, which is the large bolt on the top of the stem. Tap the top of the bolt down with a soft mallet or a piece of wood to disengage the quill from the inside of the steerer tube. Set the stem so your handlebars are at your desired height. Make sure that the stem is inserted beyond its height-limit line and that it is lined up correctly with your front wheel. Tighten the stem anchor bolt.
Changing Mountain Bike Stem
If you have to drastically change the length of your mountain bike stem in order for your mountain bike to fit you comfortably, it is likely that your frame is too big or too small. For more information on fitting your mountain bike, please visit our page on
Mountain Bike Fit
However, you may wish to change out your bike stem to customize the fit of your mountain bike, for style purposes, or to tailor your bike for better climbing or downhill performance.
Change Threadless Headset
To take out your threadless headset, unscrew the large bolt that is on the top of the steerer tube. Loosen the 2 small bolts that attach the stem to the steerer tube.
Usually these threadless bike stems have 2 or 4 bolts that attach a little face plate to the front of the stem. Unscrew the bolts that attach the faceplate, remove the plate, and take off the handlebars. Gently set the handlebars down so the cables do not get pulled.
To put the new stem on your bike, slide the stem onto the steerer tube. Remove the face plate from the front of the stem by unscrewing the 2 or 4 bolts. Place your handlebars in the desired position. Screw the faceplate back on the stem. In order to get your handlebars centered and rotated in the right position, it helps to stand over your bike and move them to the position you want before tightening down the face plate. Finally, screw the large bolt back into the top of the steerer tube.
Change Quill Headset
Unscrew the face plate that holds the handlebars on the front of the mountain bike stem and set the handlebars down in a position so that the cables do not get pulled. Unscrew the stem anchor bolt on top of the stem and then tap the top of the bolt down with a soft mallet or a piece of wood to disengage the stem from the inside of the steerer tube. Pull the stem out of the steerer tube.
Grease the wedge part on the bottom of the new mountain bike stem. Insert the stem into the steerer tube to desired height making sure it is not above the height-limit line and that it is lined up with the front wheel. Screw in and tighten the stem anchor bolt. Put your handlebars back on the front of the stem and reattach the faceplate to the stem.
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