Flex plate specifications are not just catalogue fields. They decide whether the starter meshes cleanly, the converter sits at the right depth, and the plate survives repeated torque cycles without cracking or vibration. For sourcing teams, the real task is to control a small set of measurable variables: tooth count, offset, thickness, runout, hardness, coating, heat-treatment state, and crank/converter interfaces. Passenger and light-commercial applications commonly sit around 260–380 mm outside diameter, 1.5–3.5 mm plate thickness, and 100–168 ring-gear teeth, but those ranges do not release a part for production. Drawings, datums, samples, and inspection records do. Driventus is an independent aftermarket manufacturer; brand names are referenced for fitment only. We supply engine and powertrain components from Taizhou, Zhejiang, with production aligned to IATF 16949:2016 and ISO 9001:2015 requirements. Use this guide as a buyer’s filter: what to measure, where mistakes usually occur, how to compare suppliers, and what to request before a sourcing programme moves from sample to mass order.
Start With the Dimensions That Can Stop Assembly
A flex plate can look correct and still be wrong. The usual failure is not a dramatic mismatch; it is a small error in offset, tooth geometry, hole location, or balance that appears only during installation or starter engagement.
Specification
What to request
Buying risk if vague
Outside diameter
Nominal OD and tolerance in mm
Bellhousing or starter clearance problems
Plate thickness
Gauge at ring area and centre section
Wrong stiffness, converter position, or fatigue behaviour
Crank bolt PCD
Hole count, PCD, hole diameter, centre bore
Bolt-up issues or off-centre rotation
Converter bolt PCD
PCD, slot width, angular spacing
Converter preload, assembly delay, or imbalance
Offset / dish
Axial distance from crank mounting face to converter face
A 0.5–1.0 mm error can affect converter engagement depth
Axial and radial runout
Actual value on an agreed datum fixture
Starter noise, vibration, or inconsistent clearance
Ring gear tooth count
Tooth count, module/DP, chamfer direction
Starter pinion mismatch; OD alone is not enough
Balance requirement
Neutral or application-specific balance
Vibration, warranty claims, or clocking errors
</tr></thead><tbody> </tbody></table>Typical sourcing discussion may include OD tolerance around ±0.25–0.50 mm, bolt-hole tolerance around ±0.10–0.20 mm, and axial runout targets around ≤0.30–0.50 mm depending on design. Treat those as quotation prompts, not final engineering limits. The customer drawing and application should control.
OE references such as 06A107065 can help identify the vehicle family. They should not replace dimensional confirmation. Release the order only after drawing comparison, sample measurement, and starter/converter fit checks.
A production-ready RFQ states the datum scheme, tolerance call-outs, inspection method, sample reference, and annual volume. If a supplier cannot explain exactly where OD, offset, and runout are measured, the quote is still incomplete.
Material Choice: Where Cheap Steel Becomes Expensive
Material decisions show up later as cracked bolt circles, elongated holes, noisy starter engagement, or plates that lose their formed shape. Flex plates are commonly made from low- to medium-carbon steel strip or sheet, then blanked, pierced, formed, joined to the ring gear where applicable, stress relieved or heat treated, coated, and packed.
For aftermarket programmes, common material families include SAE 1010/1020, 1045, 50Mn, 65Mn, or equivalent grades. The right choice depends on load, formed geometry, ring-gear wear, fatigue requirement, and the original drawing. Price alone is a poor selector.
Ask the supplier to define:
Steel grade or equivalent chemistry range, with mill certificate for production batches
Material thickness tolerance, such as ±0.05–0.10 mm where applicable
Heat-treatment method and target hardness, for example 28–42 HRC on hardened ring-gear areas when specified
Core plate hardness or tensile range where fatigue performance is critical
Ring-gear process: weld, shrink-fit, laser-join, or integral forming, with pull or torque verification if used
Stress-control method after forming, especially for dished plates and high-offset designs
A plate that is too soft can dish, fret, or elongate holes. A plate that is too hard can crack at bolt holes, lightening windows, or stamped relief features. Both problems may pass a simple visual inspection.
For export programmes, confirm REACH (EC) No 1907/2006 where applicable, especially for coatings, passivation, oils, and surface treatments. Also request batch traceability from steel coil to finished carton, plus hardness, coating, and dimensional inspection records. Our quality system details are outlined at quality system.
Inspection Is the Difference Between a Spec and a Promise
Flex plate specifications only matter when they are linked to gauges, fixtures, datums, and sampling rules. A number on a drawing is not enough. Buyers should ask how each critical feature is checked at first article, during production, and before packing.
Inspection points that deserve evidence
Outside diameter, ring gear OD, and pitch circle diameter by calibrated fixture, height gauge, optical comparator, or CMM
Thickness by micrometer at defined points, often 6–8 positions around the plate
Flatness, dish height, and axial runout on a reference mandrel or crank-face simulation fixture
Hole position, slot width, and angular spacing by CMM, go/no-go gauges, or dedicated checking fixture
Tooth count, tooth profile, chamfer orientation, and burr condition by visual and profile inspection
Hardness by Rockwell or equivalent method on the plate and ring gear area where specified
Surface defects, burrs, cracks, and weld condition by visual check and, where required, magnetic particle or dye penetrant methods
For high-volume programmes, ask for an inspection plan with sample size, control frequency, gauge calibration status, and reaction plan for out-of-tolerance parts. A practical package may include 5-piece first article inspection, 100% visual check, hourly runout checks during stamping/forming, and AQL-based final inspection before packing.
Do not ignore packaging. Runout can be lost after inspection. A plate that leaves the fixture within tolerance can arrive bent or nicked if it is stacked metal-to-metal without separators, edge protection, or carton compression limits. Packaging is part of dimensional control, not an afterthought.
Fit Validation: The Eight Checks Before You Scale
Bolt-pattern compatibility is only the first gate. A working flex plate must also place the converter correctly, mesh with the starter, clear the housing, and maintain the required balance condition under installation torque.
Validation sequence: 1. Confirm OE part number, engine code, transmission code, production year range, and market variant. 2. Verify crank bolt pattern, centre bore, pilot interface, and bolt-head seating surface. 3. Check converter bolt pattern, slot direction, offset, and converter-to-pump engagement depth. 4. Compare starter ring gear tooth count, chamfer direction, tooth pitch, and starter pinion mesh. 5. Confirm axial clearance to bellhousing, rear cover, sensor targets, and nearby brackets. 6. Review mass, neutral balance, external balance, clocking marks, and any added weights or drilled balance holes. 7. Measure sample runout after installation torque, not only on the loose part. 8. Validate with a sample build and record installation torque, noise, and starter engagement results.
The common trap is approving the part on a bench measurement only. A sample can match the bolt pattern and still create starter wear, converter preload, pump damage, or vibration if the offset is wrong by 0.5 mm or the chamfer faces the wrong direction.
For fleet, distributor, and repair-chain buyers, a 5–20 piece validation run is usually more valuable than a larger initial discount. For new or reverse-engineered programmes, use this release path: sample measurement, drawing confirmation, first article inspection, bench fit, vehicle or engine-stand trial, packaging drop/stack check, then pilot order. Driventus supports custom manufacturing for programmes that need drawing-based dimensions, special coatings, controlled packaging, or private-label cartons.
RFQ Scorecard: Compare Suppliers on More Than Unit Price
A useful RFQ makes engineering and commercial risk visible at the same time. If two suppliers quote the same flex plate but one controls runout, hardness, packaging, and traceability while the other lists only an OE reference, the prices are not comparable.
Include in the RFQ pack:
Application name, engine code, transmission code, production years, and OE cross-reference if known
2D drawing, 3D file, or sample part for dimensional review and reverse engineering
Annual volume, first order quantity, release schedule, and forecast by quarter
Target material grade, thickness, hardness, coating, runout, and balance requirements
Inspection report format, PPAP/FAI requirement, traceability level, and sample approval process
Packaging, labelling, barcode, carton strength, pallet height, and mixed-SKU rules
Country of destination, incoterms, HS code expectations, and required shipping method
Target price range or current landed-cost benchmark if available
Commercial terms change by programme type. Existing catalogue items may support lower MOQs, often around 100–300 pieces per SKU depending on stock and packaging. Custom or low-demand SKUs may require 300–1,000 pieces to absorb tooling, fixture, sampling, and setup costs. Reverse engineering, new tooling, or special coating may be charged separately or amortised across early production orders.
Separate lead time by stage. Drawing review and quotation can often be completed in several working days when data is complete. Sample production commonly takes 20–45 days depending on tooling and heat treatment. Mass production is typically 30–60 days after sample approval and deposit, before sea freight, customs, and local distribution.
Price is usually driven by steel grade and thickness, tooth count, forming complexity, ring-gear process, hardness requirement, runout tolerance, inspection level, packaging, order quantity, and exchange-rate or steel-cost movement. If you are still building your source list, review our catalog and the engine component range at /products/engine-components.html. For pricing, MOQ, sample, and lead-time discussion, use request a quote.
A supplier with IATF 16949:2016 and ISO 9001:2015 certification should be able to quote against these points without guesswork. That is the baseline expected by buyers in the EU, UK, US, Canada, Australia, and Brazil.
Frequently asked questions
The critical flex plate specifications are outside diameter, thickness, crank and converter bolt circles, offset, tooth count, runout, balance condition, material grade, hardness, and coating. These determine fit, starter engagement, converter position, vibration, and fatigue life.
No. OE references are useful for identification, but buyers should still verify drawings, measurements, sample fit, tooth count, offset, and runout. Driventus is an independent aftermarket manufacturer; brand names are referenced for fitment only.
Ask for a dimensional drawing, first article or inspection report, material statement, hardness record, traceability information, packaging specification, and commercial terms covering MOQ, sample lead time, production lead time, and incoterms. For regulated coatings, confirm REACH (EC) No 1907/2006 where relevant.
If you need a quote, MOQ check, drawing review, or sample-based confirmation, contact Driventus through /contact.html.
