Clutch release (throw-out) bearings · Mechanical fork-operated versus hydraulic concentric slave cylinder, self-centring, sealing and grease for clutch heat, fit and orientation
A clutch release bearing (throw-out bearing) sits on the gearbox input guide tube and presses on the clutch's diaphragm spring fingers when the driver depresses the pedal, letting the rotating clutch release while the bearing's non-rotating side is pushed by a fork or a hydraulic slave cylinder. Ask three things first: which actuation it uses (mechanical fork or hydraulic concentric slave cylinder) and which vehicle and clutch it must fit, how it centres itself on the diaphragm spring, and how its seals and grease cope with clutch heat and dust.
Clutch release bearings for manual transmissions in cars, light and heavy commercial vehicles, mechanical (fork-operated) and integrated in hydraulic concentric slave cylinders (CSC). Clutch discs and pressure plates, master cylinders and dual-mass flywheels are outside this page except where compared.
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01
Trans Power describes its clutch release bearings (also called throw-out or clutch bearings) as covering cars, pickups, buses and medium and heavy trucks in two families: mechanical bearings operated by a fork and linkage, and hydraulic release bearings, including concentric slave cylinders (CSC), where hydraulic pressure pushes the bearing directly with no fork or linkage and adjustment is automatic through the life of the part. Its comparison table gives grease loss and seal wear from clutch heat, and noise with the pedal down, as the failure pattern for mechanical bearings, and the same plus hydraulic seal leakage for hydraulic units. [1]
LuK's fitting instruction for a concentric slave cylinder (VW Transporter T4, LuK 510 0016 10) states that the flat side of the release bearing must face the clutch; if the bearing is refitted the wrong way round, its guiding ridge grinds on the diaphragm spring and the thrust block grinds on the CSC housing, causing premature failure. [3]
Editorial note: release bearings are application-specific; give the supplier the vehicle, transmission and OE or cross-reference numbers, and check the bearing's contact face, sleeve bore and fork or CSC interface against the old part.
Give the supplier the vehicle make, model, engine and transmission, OE or cross-reference part numbers, actuation type (fork or CSC), clutch type, operating conditions (heavy duty, stop-start, high temperature), quantity and packaging, and any bench-test or warranty requirements.
02
US patent 4,080,019 (Self-centering clutch release bearing) describes a ball bearing with stamped thin-walled races, whose inner race is pushed by the clutch fork while the outer race's toric face bears on the diaphragm; a sleeve fixed inside the inner race carries a resilient or plastic ring that slides on the gearbox guide tube, so the bearing can move radially to centre itself on the diaphragm during disengagement and then stay centred by the resilient axial pressure between sleeve and ring. [2]
Trans Power states that it sets raceway grinding accuracy and clearance for quiet running with the pedal down, matches grease to clutch-housing temperature because grease breakdown ends bearing life, and chooses seals to keep clutch dust and oil out of the raceway. [1]
Editorial note: ask the supplier for the grease temperature range, seal type, noise test and any self-centring feature, and for bench-test samples before volume orders.
03
NSK's May 2007 release on its TRZ series of self-aligning clutch release bearings for small manual-transmission cars reports a weight reduction of more than 40% against its earlier design, from fewer parts held by a clamping spring and from moving parts to resin. It reports about twice the high-temperature durability of a general mineral-oil grease from a dedicated grease with a urea thickener and a blended synthetic and mineral base oil, a race steel developed for good press forming and shorter heat treatment at unchanged durability, and a glass-fibre polyamide resin with an added wear-resistant polymer that reduced wear of the mating aluminium part. NSK's December 2013 release on a high-reliability release bearing for markets with flooded roads explains that clutch housings now have air holes for cooling, which let muddy water reach the bearing; its answer was an eave-shaped seal lip with an added labyrinth, a drain groove between the bearing and the sliding part, and friction loss kept equal to the earlier seal. [4] [5]
Editorial calculation: on a release bearing that weighed 200 g, a reduction of more than 40% would bring it below 120 g. Ask a supplier which of these features its bearing has, and for test data behind each claim: grease life at your clutch-housing temperature, a muddy-water ingress test for vented housings, and wear on the guide tube material. [4] [5]
| Design change | Reported result | Ask the supplier for |
|---|---|---|
| Fewer parts, clamping spring, resin parts | Over 40% lighter [4] | Weight; part list. |
| Dedicated urea grease, blended base oil | About 2× high-temperature durability vs mineral-oil grease [4] | Grease and life test. |
| Wear-resistant glass-fibre polyamide | Less wear on aluminium mating part [4] | Sleeve material. |
| Eave-shaped lip with labyrinth | Better sealing at equal friction [5] | Ingress test. |
| Drain groove | Muddy water does not stay in the bearing [5] | Housing venting. |
04
Trans Power and Prorun list concentric slave cylinders as well as mechanical release bearings; Starwex, Tinafor, AMC Power and FSK list release bearings beside wheel, tensioner, pulley, gearbox or roller bearings.
Ask each of them for cross-reference coverage, actuation type, self-centring design, seals and grease, noise and life testing, and packaging.
05
The first four rows follow the fork-operated ball bearing in US 4,080,019; the seal, grease and CSC rows come from Trans Power's page and LuK's fitting note.
| Part | Role | Fix in the order |
|---|---|---|
| Inner race and sleeve | Pushed by fork; slides on guide tube. [2] | Bore; sleeve material. |
| Outer race contact face | Bears on diaphragm spring. [2] [3] | Face profile; orientation. |
| Balls and cage | Carry thrust while rotating. [2] | Size; cage. |
| Self-centring ring | Allows radial shift. [2] | Material; design. |
| Seals and grease | Keep out dust; survive heat. [1] | Seal type; grease range. |
| CSC piston and seals (hydraulic) | Push bearing directly. [1] [3] | Fluid; seals. |
06
Release bearings are matched to a vehicle and transmission, so the sources here give no bore, load or speed values; only the sealing row carries a published design example.
| Field | What it means and published values | Ask the supplier for |
|---|---|---|
| Bore Diameter (mm) | Fits guide tube. [2] | Bore. |
| Outer Diameter (mm) | Contact with diaphragm. [2] | Diameter. |
| Width (mm) | Installed length. | Width. |
| Dynamic Load Rating (kN) | Thrust capacity. | Rating. |
| Static Load Rating (kN) | Thrust capacity. | Rating. |
| Max Speed (rpm) | Engine speed. | Rating. |
| Operating Temperature (°C) | Clutch housing heat. [1] | Grease range. |
| Radial Clearance (mm) | Noise and life. [1] | Clearance. |
| Axial Displacement (mm) | Release travel. | Travel. |
| Sealing Type | Dust and oil exclusion; e.g. eave-shaped lip with labyrinth and drain groove. [1] [5] | Seal design. |
| Material Grade | Races and sleeve. [2] | Steel; plastic. |
| Weight (kg) | Handling. | Weight. |
07
Paste it into your enquiry below or into an email to a maker, then replace every bracket.
Vehicle: [make; model; engine; transmission] Reference: [OE or cross-reference numbers] Actuation: [fork; CSC] Clutch: [type; duty] Quality: [noise test; grease range; seals] Samples: [bench test before bulk] Packing: [brand; private label]
6 companies list this product among what they make. Company figures are quoted from each company's own website; every card states where the relationship came from.
Lists mechanical clutch release bearings and hydraulic concentric slave cylinders.
Product scope checked 2026-10-11
Lists clutch release bearings with wheel, tensioner and needle bearings.
Product scope checked 2026-10-11
Lists clutch release bearings with tensioner and alternator pulleys.
Product scope checked 2026-10-11
Lists clutch release bearings and concentric slave cylinders with wheel hubs.
Product scope checked 2026-10-11
Lists clutch release bearings with wheel hub and gearbox bearings.
Product scope checked 2026-10-11
Lists clutch release bearings with tapered and cylindrical roller bearings.
Product scope checked 2026-10-11
Explore company information and manufacturing capabilities, then discuss the scope of your project with a relevant supplier.
A mechanical bearing is pushed by a fork and linkage; a concentric slave cylinder pushes the bearing hydraulically with no fork (Trans Power). [1]
Trans Power cites grease loss and seal wear from clutch heat and noise with the pedal down; hydraulic units can also leak. [1]
Yes; LuK warns that a reversed bearing on a CSC grinds on the diaphragm spring and housing and fails early. [3]
One bearing maker explains that vented clutch housings let muddy water reach the bearing; it added an eave-shaped seal lip with a labyrinth and a drain groove while keeping friction loss unchanged. [5]
Sources checked 2026-10-12. The US patent describes a self-centring design in its own terms; LuK's fitting note and Trans Power's page describe their own products, and NSK's 2007 and 2013 press releases report changes to its own release bearings.
Ask for use case, specification boundaries, supplier type, and RFQ preparation information for this product.
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