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Changing the Stem

Depending on your body type and riding style, you may ride better with a replacement stem. The stem is the metal part that connects the steering mechanism to the handlebars. There are two variables: the length of the stem, and the angle that it rises away from the steering tube.

How the stem affects your riding:  

The photos in this section assume that you're riding a real mountain bike with a newer threadless headset. But the same principles apply to stems in threaded headsets.

A long stem means that you move your hands and arms more as you steer. The handlebar moves laterally in the direction of the turn (towards the side), as well as twisting further in a front-to-back direction. This throws more of your body into the turn. A longer stem allows you to put more weight on your front end. This makes it easier to fight your way up ledges, uphill switchbacks, and brutal steeps.
A short stem steers with less arm and body motion. This can make the bike feel a bit unstable to some bikers. A short stem lets you get back further over the rear of the bike during spooky downhills, because the handlebars are closer to the back end. But also, because it doesn't take as much arm motion to steer, you can hang back more when it comes time to TURN the bike while heading downhill.

A riser stem angles upward, putting the handlebars higher. Bikers with long bodies, but not overly long arms, will find a riser stem more comfortable for maintaining balance. It can also be easier on the back. A riser stem makes it easier to get back during steep downhills. It may be harder to throw your weight onto the handlebars during a climbing maneuver with a riser stem, because as the bike tilts up, you lose the forward leverage that a flat stem gives you, and the handlebars are a bit higher in relation to your chest. For a given length of stem, a riser makes the stem behave like a shorter one during steering.

Summary: Long and flat = advantage uphill, "body" steering. Short and high = advantage downhill, "twisting" steering. For more information on selecting a stem (and how it affects the "fit" of your bike), see our page on fitting the bike to your body.

Placing a new stem:

Loosen the bolts that connect the stem to the steering mechanism. If the headset is covered by a cap (like in the photo), you may need to unscrew it before the stem will slide off the headset.
Note the position of the brake levers (how horizontal or vertical they are). Now remove the bolts that hold the handlebar onto the stem. Carefully lower the handlebar, being careful not to kink any cables or break any wires!

Slide the stem up off the headset.

Put the new stem into position. The stem in the photo comes with spacing rings. This has the same effect as a riser stem -- it puts the handlebars higher. (Note: if you add spacing rings, the topmost bolt on the stem should NOT be above the end of the headset tube.)

This bike is being geared up as a downhiller -- short stem, high handlebars.

Sight down onto the front wheel to match the angle of the stem to the wheel. Tighten the bolts to secure the stem onto the headset.
Replace and tighten the headset cap.

Now put the handlebars in the receiver at the end of the stem, and loosely attach the end plate.

Center the handlebar and rotate it so the brake levers and shifters are in their former position. Now tighten it down.

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