Understand Headset Bearing Measurement
- Bike Bearing Store Team
- 2 days ago
- 4 min read
This guide explains how to check or measure headset bearings accurately and purchase the right headset bearing.
How to Identify and Measure Your Headset Bearing
Headset bearings come in many sizes and designs, and identifying the correct one can be confusing without proper measurement.
Step 1 — Look for Size Markings
Many bearings include etched size information on the side. If complete size details are shown (e.g., inner diameter, outer diameter, width), you can use this as your reference.
If only a manufacturer code is present, or there’s no visible size information, you’ll need to measure the bearing.
Step 2 — Use a Calliper for Precise Measurement
A digital or vernier calliper will give the most reliable measurements. To identify a headset bearing correctly, measure:
Inner Diameter (ID)
Outer Diameter (OD)
Width (W)
Internal chamfer angle
External chamfer angle
Which Dimensions Matter Most?
Outer Diameter and Width must match exactly to fit the bearing into the head tube.
The inner diameter must allow the steerer tube to pass through freely. A slight clearance (up to ~0.4 mm) is acceptable as long as it doesn’t contact the steerer.
For example, if your existing bearing’s ID measures 30.15 mm, a bearing with a 30.20 mm ID is usually suitable.
What About Chamfer Angles?
Headset bearings often include chamfered edges on both the inner and outer races. These chamfers help locate the bearing in the headset and improve how the assembly handles compression forces.
Chamfer angles commonly found in headset bearings include:
36°
45°
Or a mix (e.g., 36° on one side and 45° on the other)
Because these angles affect how the bearing seats in the head tube and fork, matching them when replacing bearings is important.
Preconditioning: Rotation & Break-In
Headset bearings rarely spin continuously during riding; even on long rides, they mostly oscillate slightly as the handlebars turn. This limited movement means grease may not distribute evenly inside the bearing, and seals may never fully bed in.
To ensure optimal performance straight away, Bike Bearing Store pre-rotates and breaks in the bearings before shipping. This helps settle the grease and seals, so once installed, the bearing performs at its best immediately.
Common Headset Bearing Sizes
For your reference and convenience, we have listed the available headset bearing sizes below for selection.
You can purchase them through our online store – Headset Bearings.
Format: ID × OD × Width (mm) — internal chamfer Angle × external chamfer Angle
27.15 × 38 × 6.3 mm — 45° × 45°
27.15 × 38 × 6.5 mm — 36° × 45°
30.05 × 42 × 7 mm — 36° × 45°
30.15 × 39 × 6.5 mm — 45° × 45°
30.15 × 41 × 6.5 mm — 36° × 45°
30.15 × 41 × 6.5 mm — 45° × 45°
30.15 × 41 × 6.5 mm — 90° × 90°
30.15 × 41 × 7 mm — 45° × 45°
30.15 × 41 × 7.1mm — 45° × 90°
30.15 × 41 × 6.5 mm — 45° × 90°
30.15 × 41 × 7.7 mm — 36° × 45°
30.15 × 41.5 × 6.5 mm — 36° × 36°
30.15 × 41.8 × 6.5 mm — 45° × 45°
30.15 × 41.8 × 6.5 mm — 90° × 90°
30.15 × 41.8 × 7 mm — 36° × 45°
30.15 × 41.8 × 7 mm — 45° × 45°
30.5 × 41.8 × 7.7 mm — 45° × 45°
30.5 × 41.8 × 8 mm — 36° × 45°
30.5 × 41.8 × 8 mm — 45° × 45°
30.5 × 41.8 × 8 mm — 45° × 45°
32.4 × 43.8 × 7 mm — 45° × 45°
32.8 × 41.8 × 6 mm — 45° × 45°
33 × 44 × 6 mm — 36° × 45°
33.05 × 43.8 × 7 mm — 90° × 90°
34.1 × 46 × 7 mm — 45° × 45°
34.1 × 46.8 × 7 mm — 45° × 45°
34.1 × 46.9 × 7 mm — 45° × 45°
35 × 44 × 5.5 mm — 36° × 45°
35 × 45.3 × 7.3 mm — 45° × 45°
35 × 47 × 7 mm — 36° × 45°
35 × 47 × 8 mm — 45° × 45°
36.8 × 45.8 × 6.5 mm — 45° × 45°
37 × 46.9 × 7 mm — 45° × 45°
37 × 48 × 7 mm — 45° × 90°
37 × 49 × 6.5 mm — 36° × 45°
37 × 49 × 7 mm — 45° × 45°
39.7 × 50.8 × 7.14 mm — 90° × 90°
40 × 51 × 6.5 mm — 45° × 45°
40 × 51 × 7 mm — 45° × 45°
40 × 51.5 × 7 mm — 45° × 45°
40 × 51.8 × 8 mm — 36° × 45°
40 × 51.8 × 8 mm — 45° × 45°
40 × 51.8 × 8 mm — 90° × 90°
40 × 51.9 × 7 mm — 45° × 45°
40 × 51.9 × 8 mm — 45° × 45°
40 × 52 × 6.5 mm — 36° × 45°
40 × 52 × 6.5 mm — 45° × 45°
40 × 52 × 6.5 mm — 90° × 90°
40 × 52 × 7 mm — 36° × 45°
40 × 52 × 7 mm — 45° × 45°
40 × 52 × 7 mm — 90° × 90°
40 × 52 × 7.5 mm — 45° × 45°
40 × 52 × 8 mm — 45° × 45°
40 × 52 × 12 mm — 45° × 45°
40 × 53 × 7 mm — 45° × 45°
40.5 × 49.5 × 6.5 mm — 45° × 45°
42 × 52 × 7 mm — 45° × 45°
46 × 60 × 8 mm — 45° × 45°
50 × 61.9 × 8 mm — 36° × 45°
Need Help Identifying Your Bearing?
It’s not always easy to figure out what you need, and we’re here to assist!
If you’re unsure about your bearing size or markings, send us a photo of:
The old bearing
Any numbers or markings on the side of the bearing
Your calliper measurements (if available)
Email: info@bikebearingstore.com.au
