What are Tier 1, Tier 2 and Tier 3 automotive suppliers?

Tier 1 suppliers sell systems directly to vehicle OEMs, Tier 2 suppliers make components for Tier 1 suppliers, and Tier 3 suppliers provide raw or semi-finished materials to the tiers above.

What are Tier 2 suppliers?

They are component manufacturers, for example machining, casting or stamping specialists, that build parts to Tier 1 drawings and quality requirements.

Who is a Tier 1 automotive supplier?

A company that designs and supplies complete systems or modules directly to the OEM, such as seating, axles or e-drive units.

What is a Tier 3 supplier?

A supplier of raw materials or basic semi-finished products, such as bar stock, ingot or coatings, to Tier 2 and Tier 1 manufacturers.

What documentation does a precision machining supplier provide?

Typically first article inspection (FAI) and dimensional inspection reports, CMM data and material traceability. We supply these on request, and parts are made under an ISO 9001-certified quality system. PPAP-style documentation on request (to validate by DEK).

Home Blog Tier 1 vs Tier 2 Automotive Suppliers: How the Supply Chain Works

Tier 1 vs Tier 2 Automotive Suppliers: How the Supply Chain Works

Last updated: October 2026

A vehicle maker (the OEM) buys few parts directly. Most of a car reaches the assembly line through a pyramid of suppliers: Tier 1 suppliers deliver complete systems to the OEM, Tier 2 suppliers make the components inside those systems, and Tier 3 suppliers provide the materials.

A tier 2 automotive supplier therefore supplies parts or sub-components to Tier 1 suppliers rather than directly to the OEM, although many companies work at both levels depending on the program. Knowing who is responsible for what at each level helps engineers and buyers choose the right supplier for each stage of a program.

OEM, Tier 1, Tier 2, Tier 3: definitions

Level	Supplies to	Typical products	Example
OEM	End customers, through dealers or direct sales	Complete vehicles	A vehicle brand that designs, assembles and sells cars
Tier 1	The OEM	Systems, modules: seats, axles, e-drive units, brakes, battery packs	A system supplier that ships a finished e-drive unit to the OEM plant
Tier 2	Tier 1 suppliers, sometimes the OEM	Machined housings, castings, stampings, fasteners, electronic parts	A machining supplier that makes the housing of the e-drive unit
Tier 3	Tier 2 and Tier 1 suppliers	Raw and semi-finished: bar stock, aluminum ingot, extrusions, coatings	A mill or extruder supplying aluminum bar to the machining supplier

The levels describe a relationship, not a company size. The same company can be a Tier 1 supplier on one program and a Tier 2 supplier on another.

The chain beyond Tier 3 is often called “Tier n”.

What does a tier 2 automotive supplier do?

A Tier 2 supplier manufactures components to the drawings and quality requirements of its customer, usually a Tier 1 supplier and sometimes the OEM. Most Tier 2 suppliers are process specialists: machining, casting, stamping, forging, plastic molding or electronics assembly.

They choose the process route, fixtures and inspection plan that produce the part; they do not design the system the part goes into. Precision CNC machining is a typical Tier 2 process, and it is the core of our automotive machining services.

The Tier 2 supplier is responsible for part quality and delivery: dimensions, material, finish, documentation and on-time shipment.

Its own suppliers (material, heat treatment, coating) are Tier 3, and the Tier 2 supplier manages them through sub-tier management: it passes down the requirements it received and checks that they are met.

Tier 1 vs Tier 2: key differences

Topic	Tier 1 supplier	Tier 2 supplier
Design responsibility	Designs the system or module, often with the OEM	Builds to the customer’s drawing; may suggest DFM changes
Contract	Directly with the OEM	With the Tier 1 supplier, or with the OEM for some parts
Validation scope	Validates the system to OEM spec (durability, function, safety)	Validates the part against the drawing (dimensions, material, finish)
Typical size	Often large, multinational groups	From specialist workshops to large component groups
Documentation flow-down	Receives OEM requirements and passes them down	From Tier 1; passes material and process requirements to Tier 3

What OEMs and Tier 1s expect from component suppliers

These expectations are general market practice; they vary by customer, program and volume.

A documented quality management system. The certification required depends on the customer and the program.
APQP and PPAP on series production programs. Advanced product quality planning leads to a production part approval submission, with a Part Submission Warrant (PSW) at the level the customer requests; PPAP documentation explained.
Process risk analysis and control plan. A PFMEA, often to the AIAG-VDA FMEA handbook, and a control plan that defines how each characteristic is checked.
SPC and MSA. Statistical process control on critical characteristics and measurement system analysis of the gauges used to check them.
IMDS material data. Material composition reported in the International Material Data System.
Traceability. Material certificates, supplied on request, and lot traceability from raw material to shipped part.
Capacity and run-at-rate. Proof that the process produces the agreed rate with the agreed quality.
Customer-specific requirements (CSRs) and cost-down. Each OEM adds its own rules, and annual price reductions are common on long series programs.

Expectations differ between stages. A large-series program asks for the full set.

An engineering, validation, pilot or low-volume project usually asks for inspection reports on request, material traceability and fast engineering response, with the series documentation agreed later if the program goes to production.

When component suppliers work directly with OEM engineering teams

The pyramid is not always followed. Component suppliers often work directly with the OEM or with a technology company in these cases:

EV and ADAS start-ups that design their own systems and buy machined parts directly.
Engineering and validation phases, when OEM engineers need parts to the current drawing revision before a Tier 1 supplier is chosen.
Pilot builds and pre-series vehicles.
Low-volume and specialty programs, where the volume does not justify a full Tier 1 structure.
Specialty vehicle engineering teams that order machined parts in batches to their own drawings.
Test equipment and fixtures bought directly by OEM engineering or purchasing.

Where DekAutomotive fits: precision machining for OEM engineering teams and Tier suppliers

We machine components to drawing for EV components and ADAS programs, battery and thermal parts, automotive electronics housings, and powertrain components and chassis parts.

Our work covers engineering samples, pilot batches, low-volume batches and repeat production, rather than large-series production.

The documents we provide on request are described under quality and inspection: FAI and inspection reports, CMM reports, and material certificates with traceability.

With each quotation we add DFM feedback and process-route suggestions to reduce cost and risk. Company background is under about DekAutomotive.