Stem Removal & Installation: Threadless

1

Getting started

What tools do I need?

Tape measure

Appropriate size

Hex keys or Torx® compatible keys

Torque wrench or torque screwdriver

with suitable end caps

Grease

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thread lock

for stem bolts

assembly compound

for carbon bars

Toe straps/zip ties p>

Cloths

A "threadless" stem refers to a system in which a fork with a threadless steerer tube extends through the steerer tube. A stem (A) then clamps around the outside of the steerer tube with spacers (B) if needed. Finally, a top cap (C) holds everything in place and serves as an adjustment for the helmet.

Threadless stem (A), spacers (B) and top cap (C)

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Many older bikes and some lower end bikes have threaded kingpins. The rods used with these systems are called "feather rods". For more information, see

Removal & Installation: Quill Stems

Threadless stems will typically have 1-3 pinch bolts (D) used in conjunction with a compression slot (E) to hold the stem to the steerer tube. They will also have 2-6 bolts (F) securing the face plate (G), although in some cases they will hook on one side and bolt on the other.

Pinch bolts (D) and compression slot (E)

The front plate bolts (F) and the front plate (G)

Stems are available in different head tube and handlebar sizes. It is wise to measure your components to ensure you are installing or ordering the correct stem. Some common handlebar diameters are 22.2, 25.4, 26.0, 31.8, and 35mm. There are outliers on some older bikes. Common steerer tube diameters are 1′′, 1 1⁄8", 1 1⁄4", and 1 1⁄2".

To determine the head tube and bar diameters, measure where the stem will clamp using a metric caliper. Be sure to be precise as some clamp diameters are within fractions of a millimeter of each other and are not compatible with each other.

It is difficult to determine the clamping diameter of the rod by measuring it. The collet diameter is usually stamped or labeled on the shank, but sometimes it is not. Incompatible components can be a safety hazard, so always check with the manufacturer for specifications and compatibility information.

Measure the center of the bar

Shank size is often marked on the shank

Stems also come in different lengths - measured from the center of the head tube to the center of the bar - and angles - usually between 0 and 20 degrees. These measurements are usually marked somewhere on the rod or its packaging. The rods can be installed in the up or down position to adjust the height of the bar without changing the orientation of the spacer. This is often referred to as positive and negative augmentation. When making drastic changes to the angle or length of the stem, modifications to the housing length may be required.

The positive rise (top) and the negative rise (bottom)

Stems are usually accompanied on the steerer tube by spacers. These spacers are available in a multitude of different thicknesses, colors and materials. They allow height adjustment and also play a role in adjusting the headset.

When installing a new stem, it is important to pay attention to the height of the stem and the amount of spacers you were using before. . If you want to match the height of the stock stem, measure from the top of the tire to the center of the handlebar and write it down for future reference. Note that a new stem may have a shorter or taller stack, which you will then need to account for with more, less, or different spacers.

Steering column spacers can be moved above or below the stem to change bar height.

Measure at the center of the bar clamp if you want to replicate the height of the bar

This procedure can be done with the bike in a repair stand with the front wheel removed, or on the ground. It may help to straddle the bike for more stability.