Clutch pressure plate assemblies · Diaphragm spring, pressure plate and fulcrum, clamp (set) load and its change with facing wear, self-adjusting designs, fit and inspection
A clutch cover, or pressure plate assembly, bolts to the engine flywheel and uses a diaphragm spring acting on a pressure plate to clamp the clutch disc between the pressure plate and flywheel; pushing the spring's inner fingers through the release bearing lifts the pressure plate to release the clutch. Ask three things first: which vehicle, clutch disc and flywheel it must fit, what set (clamp) load the diaphragm spring gives and how it changes as the disc facings wear, and how the supplier inspects each cover.
Diaphragm-spring clutch covers (pressure plate assemblies) for cars and commercial vehicles, including self-adjusting designs. Clutch discs, release bearings, flywheels and dual-mass flywheels, and industrial or electromagnetic clutches are outside this page except where compared.
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01
US patent 4,924,991 (Clutch cover assembly with self-adjusting pressure plate) describes a diaphragm-spring clutch in which the cover is fixed to the flywheel, the clutch disc facings, pressure plate and diaphragm spring sit between flywheel and cover, the spring is held between two wire rings on stud pins as its fulcrum, and the release bearing pushes the spring's inner end to release the clutch. It explains that in a conventional cover the wear-in of the facings is limited by the load characteristic, because the diaphragm spring's incline at engagement increases as the facings wear, changing the load so the facings cannot be used to their maximum wear. [1]
The patent's design splits the pressure plate into a body and two axially movable fulcrum rings, pushed by spring-loaded wedge (slide) keys, so that as facings wear the fulcrum points rise automatically; the set load, chosen at the peak of the load characteristic when the clutch is built, is then maintained, torque transmission is not reduced by wear, and the release operation stays constant. It describes this as suiting vehicles with heavy clutch use, such as taxis and business cars. [1]
Editorial note: ask the supplier for the set load and the load-versus-wear curve of the offered cover, and whether it is a conventional or self-adjusting design, so it can be matched to the clutch disc's wear allowance.
Give the supplier the vehicle make, model, engine and transmission, OE or cross-reference numbers, clutch disc diameter and type, flywheel type, push or pull release, duty (taxi, commercial, heavy), whether a self-adjusting cover is required, quantity, and inspection and warranty expectations.
02
A 2026 Scientific Reports study of a clutch diaphragm spring shows in numbers why the patent above ties facing wear to clamp load. Its test spring has an outer diameter D = 380 mm, inner diameter d₁ = 152 mm, d = 292.3 mm, thickness δ = 4.5 mm and cone height H = 8.5 mm. Its force peaks at 17,596 N at 4.25 mm deflection and falls to a minimum of 11,730 N at 9.52 mm. Set at the mid-point of 6.88 mm, the spring gives 14,663 N, and the force stays above that value as deflection decreases by up to 4.56 mm. [4]
Editorial calculation: the minimum force is about 33% below the peak (11,730 / 17,596 ≈ 0.67), and the set-point force is about 17% below it. A spring operated on a curve shaped like this changes its clamp load as the facings wear and the deflection moves, which is the effect the self-adjusting cover in US 4,924,991 is designed to cancel. [4] [1]
The authors report that their optimised spring geometries reach up to 22% more compressive force with 12% less material volume than the reference; finite element analysis put the peak equivalent stress at 2,244 MPa, confined to small regions with equivalent plastic strain below 0.004. On the test rig at the full 17 mm actuator displacement, force varied by ±2% over 5,000 cycles, temperature rose 10–12 °C, and hysteresis losses per cycle fell by 25%. These results are for the authors' dry dual-flow clutch coupling design, not a vehicle cover rating. [4]
Ask a cover supplier for the measured load–deflection curve of the offered diaphragm spring, the set point on that curve, the clamp load at new and minimum-worn disc thickness, and any cycle test showing load drift. [4] [3]
03
Jiangsu Mensch describes itself as a clutch factory with more than 2,000 clutch disc types and about 500 clutch cover types covering Japanese, Korean, American and European vehicles, states that its products meet TS16949, and lists 100% inspection. [2]
Editorial note: clutch covers are application-specific; check bolt pattern, disc diameter, pressure plate face and release finger height against the original part, and request the inspection record for set load and release travel.
04
Suppliers linked to this page list clutch covers; each card links to the page reviewed.
The suppliers reviewed list clutch covers with clutch discs and kits; ask each for OE cross-references, set load and release load, self-adjusting options, inspection records and warranty.
05
AP Racing's 2018 cover-assembly catalogue shows the data a cover maker can publish per part number: mounting and dowel holes, set-up height (flywheel face to the diaphragm spring fingers or release plate), spring colour and finger form, clamp load in N and lb, driven plate thickness 'new clamped' and 'minimum worn', torque capacity by driven plate, maximum rotational speed and maximum release travel. It explains that while the driven plate stays between the two thicknesses the stated clamp load is within specification, and below the minimum worn figure the clamp load falls and the clutch may slip. Maximum release travel is the limit that keeps the diaphragm spring from being over-stroked. [3]
Editorial calculation: in each row the usable disc wear between new clamped and minimum worn thickness is 1.50 mm (7.11 − 5.61 and 8.38 − 6.88). The catalogue lists a maximum rotational speed of 10000 rpm for its Ø220 mm covers and states that the clutch's speed capability must be well above the maximum engine speed, which may be raised from standard. [3]
AP Racing names three factors that set clutch torque capacity: diameter, the clamp load of the cover assembly and the friction coefficient of the facings. It also ties the release bearing to the cover: a carbon thrust bearing where a release plate is fitted, a round-nose ball bearing for straight fingers and a flat-faced ball bearing for curved fingers. Ask any cover supplier for these figures for the exact part, and check set-up height against your release mechanism. [3]
06
This is a functional reference built from the sources cited; it is not one maker's design.
| Part | Role | Fix in the order |
|---|---|---|
| Cover (housing) | Bolts to flywheel; carries spring. [1] | Bolt pattern; material. |
| Diaphragm spring | Applies set load; levers release. [1] | Set load; finger height. |
| Wire rings and stud pins | Fulcrum for the spring. [1] | Type. |
| Pressure plate | Clamps disc against flywheel. [1] | Face; material. |
| Strap plates | Return the pressure plate on release. [1] | Type. |
| Self-adjusting mechanism (option) | Holds set load with wear. [1] | Fitted or not. |
07
A clutch cover quotation needs values for your vehicle. The table explains each field, gives published values where a reviewed source states them, and says what to obtain from the supplier.
| Field | What it means and published values | Ask the supplier for |
|---|---|---|
| Diameter (mm) | Matches disc and flywheel. | Disc size. |
| Height (mm) | Installed height; finger height. | Value. |
| Wall Thickness (mm) | Cover pressing. | Value. |
| Material | Cover, spring, plate. | Grades. |
| Surface Treatment | Corrosion protection. | Coating. |
| Flatness Tolerance (mm) | Pressure plate face. | Tolerance. |
| Concentricity Tolerance (mm) | Balance and run-out. | Tolerance. |
| Bolt Hole Diameter (mm) | Fixing to flywheel. [1] | Value. |
| Bolt Hole Count | Bolt pattern. | Count. |
| Weight (kg) | Handling; balance. | Weight. |
| Operating Temperature (°C) | Clutch heat. | Range. |
| Burst Speed (rpm) | Overspeed safety. | Test value. |
08
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] Clutch: [disc size; flywheel; push or pull] Duty: [taxi; commercial; heavy] Design: [conventional or self-adjusting] Quality: [set load; release load; inspection] Warranty: [terms]
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Lists clutch covers, discs and kits listed by vehicle make.
Product scope checked 2026-10-11
Lists clutch covers, plates and kits.
Product scope checked 2026-10-11
Lists clutch covers and kits for Japanese, Korean, European and Chinese cars.
Product scope checked 2026-10-11
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Product scope checked 2026-10-11
Lists clutch kits with dual-mass flywheels and clutch master and slave cylinders.
Product scope checked 2026-10-11
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US patent 4,924,991 explains that the diaphragm spring's incline at engagement grows with facing wear, changing the load. [1]
It moves the spring's fulcrum as facings wear so the set load and release feel stay constant (US 4,924,991). [1]
Mensch, for example, lists about 500 clutch cover types with 100% inspection. [2]
AP Racing's catalogue gives each cover a 'new clamped' and 'minimum worn' driven plate thickness, such as 7.11 mm and 5.61 mm; below the minimum worn figure the clamp load falls and the clutch may slip. [3]
Sources checked 2026-10-11. The US patent describes diaphragm-spring clutch covers and its own self-adjusting design; Mensch describes its own range. A 2026 Scientific Reports study gives a measured diaphragm spring force–deflection curve and cycle test results.
Ask for use case, specification boundaries, supplier type, and RFQ preparation information for this product.
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