The Wolf Tooth Performance ZS44/28.6 Upper is the top half of a zero stack headset for 44 mm head tubes and 1 1/8 in steerers. This one has the 6 mm top cover in black.

What it's for

This is the upper headset assembly only. The cup presses into the top of a 44 mm head tube and the bearing sits inside the frame. Wolf Tooth sells uppers and lowers separately, so you pair this with the lower that matches the bottom of your head tube and your fork.

How it works

Zero stack (ZS): The cup presses into the frame and the bearing sits inside the head tube, so only the top cover adds height.

Sealing: An O-ring seals around the steerer tube and a molded lip seal protects the upper bearing. Wolf Tooth describes three levels of sealing across the headset.

Bearing: Enduro sealed bearing in black oxide steel, with 36 x 45 degree bevels.

Compatibility

• Head tube: 44 mm inner diameter at the top (ZS44)
• Steerer: 28.6 mm (1 1/8 in) at the stem
• Carbon steerers: do not use a star nut. Use a compression plug, sold separately.
• How to check yours: ZS44/28.6 means zero stack, 44 mm frame bore, 28.6 mm steerer. Measure the inside of the upper head tube with calipers.

Setup and installation

• Cup: press in with a headset press.
• Stem cap bolt torque: 2 to 3 N·m, light grease on threads only. This bolt sets bearing preload. The stem bolts hold the fork.

Specs

• Size: ZS44/28.6 upper
• Top cover height: 6 mm
• Cup material: 6061 aluminum
• Bearing: Enduro black oxide steel, 36 x 45 degrees
• Color: black
• Warranty: 1 year
• Made in: USA (machined in Minnesota)