How do I measure my head tube?

Measure the internal diameter at the top and bottom of the head tube. Also measure whether it is threaded (external cups screw on) or smooth bore (internal/zero-stack cups press in).

What is a tapered head tube?

A tapered head tube is wider at the bottom (56 mm) than the top (44 mm), matching a tapered steerer fork. This provides more stiffness for braking and steering loads.

What is the difference between ZS and IS headsets?

ZS (Zero Stack) has cups that press into the head tube. IS (Integrated) uses bearings that sit directly into the frame with no separate cups. EC (External Cup) has cups that sit on top of the head tube.

Can I use a straight fork in a tapered frame?

Yes, with a reducer crown race. A 44/56mm tapered frame can use a straight 1⅛" fork with a crown race adapter that fills the larger lower bearing space.

How often should a headset be serviced?

Service headset bearings every 6-12 months: disassemble, clean, re-grease, and replace bearings if rough or pitted. A well-maintained headset lasts many years.

BikeCalcs

Headset Size Calculator — Find Your Headset Type

Identify the correct headset type and bearing sizes for your frame.

Head Tube Type

Steerer Type

Frame Type

How We Calculate This

Headset Standards

EC (External Cup): Traditional cups sit on top of the head tube
ZS (Zero Stack): Cups press into the head tube, flush with the surface
IS (Integrated): No cups, bearings sit directly in frame bore
Numbers (e.g., ZS44/ZS56) indicate the bore diameter in mm
Tapered: Upper bearing is smaller than lower (typically 44/56 or 41/52)

Frequently Asked Questions

Related Calculators

Chain Wear Calculator

Estimate chain replacement timing from mileage and conditions.

Brake Pad Calculator

Estimate brake pad life based on riding conditions and terrain.

Tyre Wear Calculator

Estimate tyre replacement timing from mileage and riding style.

Service Interval Calculator

Calculate when your bike components need servicing.

Tubeless Conversion Calculator

Plan a tubeless conversion with sealant, tape and valve requirements.

Last updated: February 2026

All calculations are estimates. Always verify results and consult a professional bike fitter where appropriate.