FSA Orbit C-40 ACB
FSA

FSA Orbit C-40 ACB

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FSA Orbit C-40 ACB is a lightweight integrated headset with ACB sealed bearings and a low 16.4mm stack. Built for 1-1/8" to 1.5" tapered steerers and compatible with carbon or alloy head tubes.

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Product Details

Overview & Technology

FSA's Orbit C-40 ACB is a compact, high-performance integrated headset engineered for modern tapered steerers. It uses FSA's ACB (Angular Contact Bearing) sealed bearings with asymmetric contact angles (upper 45/45, lower 36/45) to spread radial and axial loads across a larger contact patch, giving smoother rotation and longer service life under trail and cross-country stresses. The headset features precision-machined aluminium cups with tight tolerances and a low 16.4mm stack height to keep your front-end sleek and responsive. With a crown race seat at 40mm and SHIS sizing IS42/28.6 upper and IS52/40 lower, the Orbit C-40 is built to deliver crisp steering feel while staying lightweight at approximately 81.2g.

Key Features & Benefits

Sealed ACB bearings: The ACB sealed bearings are designed to keep grit and moisture out so steering remains buttery smooth over long miles and rough conditions. The 45°/36° contact geometry balances axial support and radial load resistance for durability under braking and impacts. • Low stack height (16.4mm) preserves headset and frame aesthetics while minimizing rise at the head tube. • Lightweight construction (~81.2g) reduces front-end mass without sacrificing strength. • Carbon and alloy compatible—precision cups and compliant sealing work on modern integrated headtubes made from either material.

Fit, Construction & Compatibility

The Orbit C-40 ACB is an integrated (IS) headset sized IS42/28.6 for the upper cup and IS52/40 for the lower cup, designed for frames with integrated headtube cups. It fits 1-1/8" (28.6mm) steerer sections into 1.5" (40mm) forks—commonly called a 1-1/8" to 1.5" tapered steerer configuration. Key specs include a 42mm upper cup OD, 52mm lower cup OD, and a 40mm crown race seat. The headset works with both carbon and aluminium head tubes; ensure your frame is an IS standard with those cup diameters before purchasing. Installation requires a headset press or compatible tools and attention to proper lubrication and torque sequencing.

Who It's For

This headset is ideal for mountain and trail riders who want a low-profile, durable integrated headset that won’t add unnecessary weight. It’s especially suitable for riders running modern tapered steerers on cross-country, trail, and light enduro rigs where smooth steering and low stack height are priorities. Mechanics and home wrenches will appreciate the sealed bearings' low maintenance and straightforward fit to IS frames; bike builders spec'ing lightweight yet reliable headsets on carbon or alloy frames will find the Orbit C-40 a smart choice.

Key Features

  • ✓ ACB sealed angular-contact bearings for smoother, longer-lasting steering
  • ✓ Low 16.4mm stack height preserves frame aesthetics and handlebar fit
  • ✓ Ultra-light ~81.2g complete headset minimizes front-end mass
  • ✓ Compatible with 1-1/8" to 1.5" tapered steerers (IS42/28.6 | IS52/40)
  • ✓ Works with both carbon and alloy integrated head tubes
  • ✓ Precision-machined cups and 40mm crown race diameter for secure fit
  • ✓ 36°/45° bearing geometry balances axial load and radial durability

Specifications

Bearing Grade ACB Sealed
Crown Race Diameter 40mm
Lower Cup 52mm
Headset Type Integrated
Upper Cup 42mm
Headset Weight 81.2g
Misc 36°/45° ACB
Primary Color Black
S.H.I.S. IS42/28.6 | IS52/40
Steerer Tube 1-1/8''-1-1/2''
Stack Height 16.4
Headset Position Complete
SHIS Upper IS42/28.6
SHIS Lower IS52/40

Product Identifiers

Vendor Item # 121-0514
UPC 400310063052

Frequently Asked Questions

Will this headset fit my frame?

The Orbit C-40 ACB is an integrated (IS) headset sized IS42/28.6 (upper) and IS52/40 (lower). It will fit frames that accept those integrated cup diameters. Confirm your frame's head tube spec (IS42/28.6 | IS52/40) before purchase.

Is the Orbit C-40 compatible with carbon head tubes?

Yes. The headset is compatible with both carbon and alloy integrated head tubes. Use appropriate press-fit techniques and shims as needed, and follow torque recommendations to avoid crushing or damaging carbon.

How do I service the bearings?

The ACB bearings are sealed for low maintenance; periodic inspection and light regreasing during fork changes or overhaul is usually sufficient. If seals are damaged or play develops, replace bearings rather than attempting aggressive teardown—replacement bearings are straightforward to press in.

What tools are required for installation?

You’ll need an integrated headset press, appropriate drift for IS cup diameters, crown race setter for 40mm crown race, grease, and hex keys for stem clamping. If you’re unsure, have a qualified mechanic press the cups to avoid frame damage.

How should I preload and torque the headset?

Preload by tightening the top cap until play is removed and steering rotates freely, then torque the stem clamp bolts to the stem manufacturer’s specification (typically around 4–6 Nm). Avoid over-torquing the top cap; final preload is set by the stem clamp bolts.

What is ACB and how is it different?

ACB stands for Angular Contact Bearing—FSA’s design uses angled contact faces to better handle combined axial and radial loads compared to standard cup-and-cone or loose-ball setups. The asymmetric angles (45/36) are tuned for steering stability under braking and impacts.

Buying Guide

When choosing an integrated headset, match the SHIS sizing (IS42/28.6 upper, IS52/40 lower) to your frame and confirm steerer compatibility (1-1/8" to 1.5" tapered). Prioritize sealed bearings, low stack height, and weight if you want a headset that stays out of the way visually while delivering precise steering. Consider how you ride: sealed angular-contact bearings like FSA's ACB are excellent for mountain use where shocks, mud, and braking loads demand durable contact geometry. If you have a carbon head tube, ensure proper installation technique and use a press to avoid damage.

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