HEADSET
BEARING

Headset bearings play a vital role in your bike’s steering performance. They sit at the top and bottom of the head tube, helping the fork turn smoothly under the load of the rider and bicycle.

Unlike bearings that primarily handle rotational (radial) forces, headset bearings are designed to carry axial loads, essentially the downward force from your weight. Because they are angular contact bearings, they are built to support this load while allowing smooth steering.

Why You Should Replace Both Bearings

Headset bearings are positioned where they are exposed to road grit, moisture, and sweat, all of which contribute to wear over time.

When one bearing becomes worn or contaminated, it’s very likely that the other is nearing the same point. Replacing both bearings together helps ensure even performance and prevents the new bearing from wearing out prematurely.

Also, angular contact headset bearings require preload. It’s normal for them to feel slightly gritty if spun by hand when unloaded; this does not mean they’re faulty. Once installed correctly, they should operate smoothly.

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 race. 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