MTB Stems

How to choose your MTB stem

The stem connects the handlebar to the fork steerer tube. Three dimensions determine fitment, and a single variable — length — genuinely alters how the bike handles.

The three essential dimensions

• Handlebar clamp diameter : 31.8 or 35 mm. It must match the handlebar diameter exactly, as no adapters can be used.
• Steerer diameter : 1"1/8 (28.6 mm), the standard across all modern mountain bikes.
• Length : from 30 to 90 mm, measured centre-to-centre.

Length: what difference it makes

• 30 to 45 mm : enduro and downhill. Highly responsive steering, rearward body weight, easier to lift the front wheel.
• 50 to 60 mm : trail and all-mountain, the most popular compromise.
• 70 to 90 mm : cross-country and touring. Stretched-out position, solid front-end weighting, better front wheel grip on steep climbs.
• A difference of 10 mm is immediately noticeable, especially on front-wheel traction during technical climbs.

Angle

0° and 6° are common values. An angled stem can be flipped, giving two handlebar heights from the same component: try this before buying a handlebar with a different rise. With a 0° stem, the handlebar stays aligned with the steerer regardless of orientation.

Direct mount fitting

On dual-crown downhill forks, the stem mounts directly to the upper or lower crown without clamping onto the steerer tube. These stems are only compatible with this type of fork, and the mounting bolt spacing must match the crown.

When fitting

• Tighten the faceplate bolts in a cross pattern and in stages, to maintain an even gap on both sides of the faceplate.
• Observe the torque values, typically 5 Nm on the faceplate and 5 to 6 Nm on the steerer clamp bolts.
• Lightly grease the bolt threads, but never the handlebar clamping surface.
• Tighten the steerer clamp bolts last, once the headset has been adjusted using the top cap.

To find out more: How to choose your MTB stem

See also: MTB handlebars · MTB headsets · Headset top caps and star nuts