Bontrager Stem


Figure 1- Adjustable angle quill-type stem

this is Bontrager marketing drivel waiting for balmer's input

The stem (Figure 1) attaches the handlebar, the part you hold with your hands when riding a bicycle, to the fork. In addition, the stem works with the handlebar to define your position on the bike.

This section explains how to inspect, adjust, and lubricate your stem.

 

Warning

An improperly adjusted or tightened stem can cause you to lose control and fall. Make sure the stem is positioned and tightened properly before riding the bike.

Stems are attached to the bike in two ways:

Figure 2- Direct-connect type stem

• Quill stems have a tube, or quill (Figure 1), fastened inside the fork by an expanding wedge.

• Direct-connect stems (Figure 2) clamp to the outside of the fork steerer.

 

Inspecting the stem

If you are unsure of the safety of your stem, do not ride the bicycle; take the bicycle to your dealer for adjustments.

Before every ride, check the stem for signs of stress or fatigue.

Test for rotation of handlebar in stem and stem on steerer
Figure 3- Test for rotation of handlebar in stem and stem on steerer

Once a month make sure the stem is in alignment with the front wheel. Test the stem connection to the fork by attempting to turn the handlebar from side to side with the front wheel locked between your knees (Figure 3). Test the security of the handlebar by attempting to rotate it in the stem.

Check that all bolts are tight. The correct tightness varies according to the type of stem on your bike; follow the torque specifications. If you are unsure of which type of stem your bike is equipped with, consult your dealer.

Tighten these bolts:

Stem expander: 175-260 lb•in (19.8-29.4 Nm).

Handlebar clamp on:

- welded stems: 100-120 lb•in (11.3-13.6 Nm)

- forged stems: 150-180 lb•in (17-20.3 Nm)

Steerer clamp: 100-120 lb-in (11.3-13.6 Nm)

Stem angle adjustment: 150-170 lb•in (17-20.3 Nm)

If your stem has any carbon fiber parts, also follow the carbon fiber composite inspection procedures.

TOP of PAGE

Adjusting the stem

To determine the best position of the stem, see Fitting the Bike .

To adjust the angle of the handlebar

1. Loosen the handlebar clamp bolt(s) on the stem just enough that the handlebar can be rotated in the stem.

2. Position the handlebar to the desired angle, making sure they are centered in the stem.

3. Tighten as shown in Inspection.

To change the angle of an adjustable-rise stem

1. Loosen the angle adjusting bolt(s) until the stem can be rotated.

2. Position the stem to the desired angle.

3. Tighten the angle adjusting bolt as shown in Inspection.

To change the handlebar height with a quill stem

Adjusting the handlebar height on a direct-connect stem affects the headset bearing adjustment. This procedure requires special tools and training so this should only be done by your dealer.

Figure 4- Minimum insertion mark

To adjust the height of the adjustable-rise stem in Figure 1, first change the stem angle, which gives access to the stem expander bolt.

1. Loosen the stem expander bolt two to three turns.

2. Tap the top of the stem expander bolt with a wood or plastic-faced mallet to loosen the stem wedge.

3. Adjust the handlebar to the desired height, but with the minimum insertion line inside the frame (Figure 4). A minimum of 2 3/4 inches (70 mm) of the stem quill must always remain in the frame.

4. Tighten as shown in Inspection.

 

Warning

An improperly adjusted or tightened stem can cause you to lose control and fall. Make sure the stem is positioned and tightened properly before riding the bike.

TOP of PAGE

Lubricating the stem

Once a year, lubricate the stem.

Note: Lubricating a direct-connect stem requires adjustment of the headset bearings, so should only be done by your dealer.

To lubricate a quill stem

1. Follow the instructions To change the handlebar height with a quill stem, and remove the stem from the frame.

2. Wipe any old grease off the stem, and clean it.

3. Apply a thin layer of Wrench Force® synthetic grease or a similar lubrication to the section of the quill that will be inserted into the frame, including the stem wedge.

4. Insert the stem into the frame, and follow the instructions To change the handlebar height with a quill stem.

For stems or handlebars made of carbon fiber composite, avoid grease of other lubricants on clamping surfaces between the stem and handlebar. Before assembling a carbon part, clean both the part and its mating surface with rubbing alcohol and a shop rag; clean until the rag shows no discoloration.


Installation instructions for the experienced mechanic

These instructions explain the steps to remove an existing stem and install a new one. The correct installation of a new Bontrager stem is critical to the rider's safety, so this work should be performed only by an experienced mechanic. If you are not sure of your ability to correctly install this stem, have the stem installed by your Bontrager dealer.

Check all parts for compatibility before installing

The stem interfaces with the fork steerer and handlebar. These parts must be compatible and the correct diameters for the stem to function correctly. If you are not sure if this stem is compatible with your bicycle, consult your dealer.

If any component is made of carbon fiber composite, make sure the connecting parts are carbon-compatible.

To remove a stem

1. Loosen and remove the handlebar clamp bolts.

2. Loosen the steerer clamp bolts.

If the bicycle is in a repair stand, or the front wheel is off the ground, support the fork to prevent it from dropping out of the frame.

3. Loosen and remove the bearing preload adjustment bolt.

4. Slide the stem off the steerer.

To install a stem

1. Loosen the steerer clamp bolts.

2. With a rag, wipe a light oil onto the surface of the steerer.

Some manufacturers tell you not to lubricate the steerer. As an example, some forks with carbon fiber steerers tell you to assemble the stem dry. If you are unsure, check with the fork manufacturer.

3. Place the headset spacers above or below the stem as desired and slide the stem onto the steerer.

Figure 5- Stem clearance over steerer

4. Make sure the steerer is between 2-3mm below the top surface of the stem or spacers (Figure 5).

5. Install the top cap and bearing preload adjustment bolt.

6. Adjust the headset.

7. Tighten all stem bolts as shown in Inspection.


Click for related topics