Home/ Blog / crankshaft pulley

crankshaft pulley · 2026-07-06

Crankshaft Pulley Specifications for B2B Sourcing

Crankshaft pulleys look simple until the first warranty pattern appears: belt walk, tensioner noise, rubber slip, cracked damping rings or a pulley that fits the crank nose but fails at speed. For B2B sourcing, the drawing is only the start. A controlled sourcing file has to define datum structure, bore and keyway limits, groove geometry, damper rubber, runout, balance, coating, marking, validation, MOQ logic, target cost and packaging controls.

This article treats crankshaft pulley specifications as a buying decision, not a generic part description. It is written for sourcing engineers, category buyers and import managers comparing production capability across Asia, Europe and the Americas. Driventus Auto Parts manufactures engine and powertrain components in Taizhou, Zhejiang, under IATF 16949:2016 and ISO 9001:2015 systems. Driventus is an independent aftermarket manufacturer; brand names are referenced for fitment identification only.

1. First Decision: Are You Buying a Pulley, a Damper or a Risk?

A crankshaft pulley transfers torque from the crankshaft nose to the accessory belt drive. On many engines it also serves as a torsional vibration damper, using a rubber or elastomer layer between the hub and inertia ring to reduce crankshaft vibration at critical speeds. That distinction changes the sourcing risk completely.

A solid machined pulley is mostly a dimensional, material and balance problem. A bonded damper is a tuned rotating assembly. A decoupled or overrunning design adds another functional mechanism. Treating all three as “a pulley” creates weak RFQs and misleading price comparisons.

Start the sourcing file by classifying the part:

Solid pulley: no damping layer; focus on bore, groove geometry, runout, balance, coating and belt line.
Bonded torsional damper: hub, rubber layer and inertia ring; add rubber compound, bonding process, ageing resistance, torsional behaviour and slip tests.
Dual-mass, overrunning or decoupled pulley: requires mechanism-level validation and stricter supplier capability review.
Combined-profile pulley: may drive serpentine, V-belt or timing systems from the same assembly; belt-line control becomes more sensitive.

A robust sourcing package normally defines:

Engine platform, displacement, engine code and model-year range for fitment mapping
Pulley type: solid, bonded damper, dual-mass, overrunning or decoupled design
Belt profile: PK multi-rib, classical V, timing belt drive or combined profiles
Crankshaft interface: bore, keyway, spline, dowel, bolt pattern or friction face
Datum scheme for axial position, concentricity and runout inspection
Rubber compound, hardness, bonding method and ageing resistance for damped versions
Dynamic balance requirement, such as residual unbalance in g·mm or balance grade
Surface protection, coating thickness and salt-spray or cyclic-corrosion requirement
Traceability marking, packaging, service-life validation plan and change-control rules

Confirm operating speed from the engine application. A passenger-car crank pulley may see 6,000–7,000 rpm engine speed, while light-commercial and performance applications can require higher overspeed margins. Outside diameter alone is not approval evidence. Two pulleys can share the same envelope and still differ in inertia, rubber stiffness and torsional tuning.

The practical risk is straightforward: a physically fitting pulley can transmit excessive torsional vibration, accelerate belt tensioner wear, shorten alternator or A/C compressor bearing life, or create noise complaints. Before nomination, request dimensional inspection results, balance data and functional test evidence, especially for bonded dampers and high-speed applications.

2. Dimensional Spec Deep-Dive: What Must Be on the RFQ Table

A useful RFQ does not say “match sample.” It converts the sample, drawing or OE service part into measurable fields. Actual values must come from the buyer drawing, an OE service sample measurement report or a jointly approved reverse-engineering report. Where no drawing exists, require measurements from at least 3–5 samples so wear and sample variation can be separated from the intended design.

</tr></thead><tbody> </tbody></table>The hidden issue is datum choice. Runout measured from the machined bore can differ from runout measured from the crankshaft-facing flange or bolt pattern. The supplier and buyer should agree whether the bore, front face, rear face or bolt-hole pattern is the primary datum. The inspection fixture should reproduce the intended assembly condition.

Example: a bolt-mounted pulley should be clamped to a master fixture with the specified bolt torque sequence before runout inspection. If it is checked loose on a bench center, the result may be repeatable but irrelevant.

For reverse-engineered aftermarket projects, Driventus typically measures multiple OE service samples and used cores where available, then builds a measurement matrix showing nominal estimate, sample spread and proposed tolerance. The engineering team separates intended design dimensions from wear, corrosion and part-to-part variation. Related rotating engine components can be reviewed in our catalog, including product families listed under engine components.

3. Material and Coating Choices: Where Cheap Substitutions Show Up Later

Material selection affects inertia, machining stability, crack resistance, bond strength, corrosion performance and cost. Buyers should require actual grades rather than generic words such as “steel,” “iron” or “rubber.” Those labels are not specifications.

Common crankshaft pulley material options include:

Grey cast iron: Often used for inertia rings where mass, machinability and damping contribution are important. Drawings may specify grades comparable to HT200/HT250 or GG20/GG25, with hardness commonly in the HB 170–240 range.
Carbon steel: Used for hubs, stamped pulley sections or welded assemblies. Common grades may include 45 steel, C45, 1045 or low-carbon stamped steel, with heat treatment and weld requirements stated separately.
Ductile iron: Selected where higher toughness is required compared with grey cast iron; nodularity, tensile class and hardness should be defined.
Aluminium alloy: Used in lightweight applications, usually with stricter control of wear surfaces, galvanic compatibility and corrosion protection. Confirm alloy, temper and anodizing or coating requirements.
EPDM rubber: Widely used for damped pulleys because of heat, ozone and ageing resistance. Typical hardness windows may be 55–75 Shore A, but the final value must match the torsional damping target.
Natural rubber or blended compounds: Sometimes used in legacy designs, subject to temperature, oil exposure and durability limits. Use only when the original design and validation support it.

Surface finish is not cosmetic. Belt-contact surfaces influence friction, wear and debris generation. A machined pulley groove may require Ra values in the approximate 1.6–3.2 μm range unless the drawing states otherwise. Mating faces often need cleaner finish control. Non-contact surfaces need corrosion resistance during transport, warehouse storage and road service.

Typical protection choices include black oxide, manganese or zinc phosphate, electrophoretic coating, zinc-based systems and painted finishes. RFQs should specify coating thickness where relevant, masking zones on bores or friction faces, and minimum corrosion performance, such as 96–240 h neutral salt spray for basic aftermarket requirements or higher cyclic-corrosion targets for severe markets. Coating selection should consider REACH (EC) No 1907/2006 for EU-market chemical compliance, as well as customer-specific restrictions on substances and surface treatments.

For bonded dampers, the rubber-to-metal interface is a critical characteristic. The RFQ should state whether the process is compression bonded, injection bonded or assembled with preformed rubber. It should also define how adhesion is verified.

Practical controls include surface blasting profile, degreasing, primer/adhesive batch control, curing time, curing temperature and post-cure inspection. Pull-off, shear, torsion or torque-slip tests should be agreed in the drawing, control plan or validation plan. If the buyer has an approved benchmark sample, test against that benchmark rather than only against an internal supplier target.

4. Failure Modes to Prevent with GD&T and Inspection Controls

A crankshaft pulley can meet basic dimensions and still fail in the vehicle. The usual reason is geometric control: the groove pack is not concentric with the crankshaft datum, the mating face is not perpendicular to the bore, or the bonded ring shifts after ageing.

Common failure modes and the controls that reduce them include:

Belt walk or edge wear: control groove axial position, groove angle, rib pitch, radial runout and installation datum.
Tensioner oscillation or belt noise: control dynamic balance, pulley eccentricity, groove finish and damper tuning.
Crank nose fit problems: control bore diameter, cylindricity, roundness, keyway width and chamfer.
Bolt-up distortion: control mounting-face flatness, perpendicularity and inspection under clamped conditions.
Rubber slip or separation: control rubber compound, bond preparation, curing, flash, voids and torque-slip performance.
Field corrosion: control coating selection, masking, thickness and corrosion test duration.

Key control points normally include:

Bore diameter tolerance, cylindricity and roundness, commonly held in the 0.01–0.03 mm range for precision machined interfaces
Perpendicularity of crankshaft mating face to bore datum, often specified as 0.03–0.08 mm depending on diameter
Concentricity or total indicated runout of belt grooves to bore datum, often 0.05–0.15 mm TIR for machined pulleys
Axial position of belt grooves from the rear mounting face, often controlled within ±0.10–0.25 mm to protect belt line
Bolt-hole true position relative to the bore datum, typically tightened for multi-bolt or dowel-located designs
Keyway location relative to timing or balance marks, where applicable
Surface roughness on the crankshaft mating face, bore and belt-contact surfaces
Dynamic balance grade or maximum residual unbalance, for example G6.3 or G2.5, or a defined g·mm limit at test speed
Rubber ring position, axial offset, flash limit, void limit and visual bond condition for damped pulleys

A practical incoming-quality plan should classify features into critical, major and minor characteristics. Critical features typically include bore fit, bolt pattern, rubber bond integrity, belt groove position, runout and balance. These items should have tighter sampling, clear acceptance limits and defined reaction plans for nonconforming lots.

For stable production, buyers may use AQL-based sampling for cosmetic and packaging checks, while requiring 100% checks for balance, visual bond defects or special characteristics when the risk justifies it.

Certified quality systems do not replace part-level specifications, but they provide process discipline. Driventus operates under IATF 16949:2016 and ISO 9001:2015, with APQP, control plans, process FMEA and measurement system analysis used where required by the customer. Buyers can review our quality system before scheduling a supplier audit.

Where statistical process control is required, the purchase specification should state capability expectations such as Cpk ≥1.33 for major characteristics and Cpk ≥1.67 for safety or critical characteristics, unless the customer standard differs. The measurement method must also be defined. Different fixtures can produce different runout values on the same pulley. Gauge R&R should be reviewed for bore, groove position, runout and balance measurements before pilot production data is accepted.

5. Validation Plan: What Evidence Is Enough Before Release?

Dimensional approval is not the same as production approval. The right test plan depends on whether the part is a solid drive pulley, a bonded torsional damper or a more complex decoupled design.

For a low-risk carryover solid pulley, full layout plus balance and corrosion confirmation may be enough. For a new bonded damper, buyers should expect material, bond, ageing, torsional and endurance evidence before shipment release.

Typical validation requirements include:

Specification item	Typical sourcing detail to request	Common control method
Overall outside diameter	Nominal OD and tolerance, often ±0.10–0.30 mm depending on process	Vernier, CMM, optical comparator
Effective belt pitch diameter	Belt pitch diameter and allowable profile deviation	Profile gauge, CMM, functional belt gauge
Overall width	Stack width and front/rear clearance, often ±0.15–0.30 mm	Vernier, CMM
Hub bore diameter	Fit class or exact limit size, commonly controlled within 0.01–0.03 mm	Plug gauge, air gauge, CMM
Keyway width and depth	Width, depth, corner radius and angular position	Keyway gauge, CMM
Bolt-hole PCD and diameter	PCD, hole size, thread, chamfer and true position	CMM, thread gauge
Rib count and rib pitch	4PK, 5PK, 6PK, 7PK etc.; PK pitch is typically 3.56 mm	Profile projector, belt gauge
Groove angle and root radius	Included angle, flank finish and root radius to prevent belt noise	Contour gauge, optical measurement
Axial runout	Target often 0.05–0.20 mm TIR depending on size and application	Dial indicator on datum fixture
Radial runout	Target often 0.05–0.15 mm TIR for machined groove packs	Dial indicator or CMM
Mass and inertia	Weight range, inertia target and balancing plane location	Balance scale, inertia rig when required

</tr></thead><tbody> </tbody></table>For emissions-sensitive applications, buyers may also need to consider the downstream effect of accessory-drive stability on engine calibration and onboard diagnostics. Vehicle emissions rules such as ECE R-83 apply to vehicles, not to a crankshaft pulley as an isolated component, but replacement powertrain parts must not compromise vehicle-level compliance when installed correctly.

Aftermarket distributors should request test summaries that identify sample quantity, equipment, test conditions, acceptance criteria, measured results and failure photographs if any. “Tested OK” is not enough for procurement records.

For multi-region sales, validation files should be retained in a format that supports importer due diligence in the EU, UK, US, Canada, Australia and Brazil. Where private-label packaging is involved, retain the test file under the buyer part number, supplier part number, drawing revision and production batch reference.

6. Reverse-Engineering Scenario: One Fitment Family, Several Hidden Variants

A common sourcing scenario: the buyer has a commercial fitment list, several OE cross-references and one sample. The pulley appears to cover multiple engine codes. The price target is aggressive. The risk is that the variants do not actually share the same inertia, offset, belt line, mounting hardware or timing reference.

For replacement programmes, the commercial fitment list must connect cleanly with the engineering specification. OE part-number cross-references should be used to organise fitment, not to imply approval by a vehicle manufacturer. If the purchasing file references a generic family such as OE 06A… or OE 11251…, the supplier should confirm the dimensional match against the exact buyer-approved sample or drawing before quotation. Driventus is an independent aftermarket manufacturer; brand names are referenced for fitment identification only.

A responsible reverse-engineering workflow normally includes:

1. Collect multiple samples from the target fitment family, ideally new OE/service parts plus field-returned cores. 2. Identify material, hardness, coating and rubber compound type using lab or supplier-confirmed data. 3. Measure functional dimensions using calibrated equipment and record sample-to-sample variation. 4. Model the component and define datum structure, including inspection clamping method. 5. Compare groove profile and belt line to the mating accessory drive layout. 6. Validate dynamic balance, inertia and damping behaviour where required. 7. Produce pre-production samples and complete dimensional full layout. 8. Lock the drawing revision, control plan, inspection gauges and packaging specification.

Do not approve based only on visual similarity. Small differences in offset, rib pitch, groove flank angle or damper stiffness can create belt squeal, edge wear, tensioner oscillation and premature customer returns. A 0.5 mm belt-line error may be visible as belt tracking movement on some drives. A rubber compound change can shift the damping peak even when the pulley looks identical.

For programmes that need a modified bore, pulley offset, coating, laser mark or private-label package, Driventus can review feasibility through custom manufacturing.

7. RFQ Checklist Plus Cost Logic: How to Compare Quotes Fairly

A clear RFQ reduces engineering loops and prevents price comparisons based on incomplete assumptions. When requesting crankshaft pulley specifications, include the following data where available:

Target market, annual volume forecast and first-order quantity
Expected MOQ range and whether stock, sample, pilot or mass production is required
OE cross-reference format, such as OE 06A… or OE 11251… when already used in the programme
Engine family, application range, belt type, rib count and installation notes
2D drawing, 3D model, approved physical sample or measurement report
Required material grades, rubber compound hardness and bonding method
Critical dimensions, tolerance class, datum scheme and GD&T notes
Runout, balance, surface roughness and coating thickness targets
Corrosion test requirement and required test duration
Marking, traceability, date-code format and country-of-origin requirements
Packaging standard, carton strength, label format, pallet configuration and drop-test requirement
Required documentation: PPAP, inspection report, material certificate, test report, IMDS or REACH declaration where applicable
Compliance expectations for REACH (EC) No 1907/2006 and other market requirements
Audit requirement, target sample date, PPAP date and production launch date

Then compare the commercial assumptions, not only the unit price. Existing designs with available tooling and standard packaging can often support lower trial quantities. New bonded dampers may need higher MOQs to absorb tooling, rubber compound mixing, bonding setup and validation cost.

Unit price is normally driven by raw casting or forging weight, machining time, groove complexity, balance correction, coating type, inspection level, documentation requirement, packaging format and freight terms. A quote for 300 pieces with full PPAP and private-label cartons should not be compared directly with a quote for 3,000 pieces using standard inspection and bulk packaging.

For production supply, also define engineering-change control. Any change to rubber compound, bonding adhesive, casting source, machining datum, coating process, balancing method or inspection fixture should be reviewed before implementation. These changes can alter field performance even when final dimensions appear unchanged.

Procurement teams comparing suppliers should ask for actual process capability, not only monthly output claims. Relevant questions include CNC turning capacity, balancing equipment range, rubber bonding press size, coating line control, gauge calibration, error-proofing, lot traceability, barcode or batch marking, and the supplier’s reaction plan for nonconforming material.

8. Q&A for Supplier Nomination: Where Driventus Fits

What can Driventus support before quotation? Driventus manufactures engine and powertrain components in Taizhou, Zhejiang, and can support sample measurement, drawing development, tooling review, pilot build planning, inspection reports and export packaging for crankshaft pulley programmes.

What production steps are controlled? Our production approach is based on controlled casting or blank sourcing, CNC turning, groove machining, defined rubber bonding processes for damped parts, dynamic balance checks where specified, coating control and documented final inspection.

Which documentation systems are available? Quality documentation can be aligned with customer requirements under IATF 16949:2016 and ISO 9001:2015 systems. For regulated markets, buyers can request material declarations, rubber and coating information, and chemical compliance review related to REACH (EC) No 1907/2006.

What affects lead time? Commercial terms depend on part complexity, tooling status, order quantity and validation scope. Existing catalogue designs usually move faster than new damper developments because tooling, rubber compound validation, bond testing and endurance trials can extend the timeline.

How should a new project start? Share drawings, samples, target volume, annual forecast, destination market, required launch date, packaging standard and documentation requirements through request a quote. Driventus does not claim endorsement or approval by any vehicle manufacturer. Brand references, when used in fitment files, are only for identifying application compatibility.

Frequently asked questions

The most critical dimensions are bore diameter, crankshaft mating face, belt groove position, outside or pitch diameter, keyway or bolt pattern, and radial and axial runout. For damped pulleys, rubber bond integrity, inertia ring alignment and balance are also critical.

Yes. Buyers should request material grade confirmation for metal parts and compound information for rubber-damped designs. Certificates should match the approved drawing or control plan and be linked to production lots where traceability is required.

Not unless the vehicle application was designed and validated for both. A torsional damper controls crankshaft vibration. Replacing it with a solid pulley can increase NVH, belt-system stress and crankshaft fatigue risk.

Yes, subject to technical review. Driventus can measure buyer-supplied samples, develop drawings, confirm materials and prepare pre-production samples. Approval should be based on agreed inspection and validation data, not visual matching alone.

If you are preparing a sourcing file for crankshaft pulleys, share the drawing, sample details, target volume and destination market with our engineering team. We can review feasibility and documentation needs through /contact.html

Request a Quote

Test	Applicable pulley type	Practical acceptance detail to define
Dimensional full layout	All types	3–5 samples measured to every drawing characteristic
Dynamic balance test	All rotating pulleys	Balance grade, rpm, correction method and max residual unbalance
Belt alignment and tracking test	All belt-drive types	Belt line offset, tracking time and no edge walk or abnormal noise
Torque retention test	Bolt-mounted or friction-mounted designs	Bolt torque, angle, slip threshold and retest after cycling
Rubber bond shear or torsion test	Damped pulleys	Minimum torque or shear value and failure mode
Heat ageing	Rubber-damped pulleys	Typical 70–150 °C exposure depending on compound and location
Ozone resistance	Rubber-damped pulleys	No cracking after specified ozone concentration, temperature and strain
Salt spray or cyclic corrosion	Coated metal parts	96, 240, 480 or 720 h target based on market and coating
Overspeed test	High-speed applications	Commonly 1.2–1.5 × maximum engine speed for defined duration
Endurance cycling	Damped pulleys	Thermal and speed cycling with no slip, crack, debond or noise issue