Design and Material Selection

The creation of a Nashville Performance CNC machined wheel begins long before any metal is cut. Engineers use advanced CAD (Computer-Aided Design) software to model every detail: spoke geometry, barrel thickness, bolt pattern, offset, and backspacing. Finite Element Analysis (FEA) simulations help predict stress points under load, allowing the team to optimize weight distribution without sacrificing strength. The choice of material is equally critical. Nashville Performance primarily sources 6061-T6 and 7075-T6 aluminum alloys—both known for their high strength-to-weight ratios and excellent corrosion resistance. 7075-T6 is often reserved for extreme-performance wheels where maximum durability is required, while 6061-T6 offers a balanced blend of workability and cost efficiency. For specialty applications, they may also use billet aluminum from certified aerospace-grade suppliers. This rigorous upfront planning ensures that every wheel meets both performance and safety targets before production begins.

Casting vs. Forging: Laying the Foundation

Once the digital design is finalized, the raw material must be formed into a cylindrical wheel blank. Nashville Performance employs two primary methods: casting and forging. Each method carries distinct advantages and trade-offs.

Casting

In the casting process, molten aluminum is poured into a permanent mold or sand mold that replicates the wheel's basic shape. After cooling, the cast blank is removed and ready for machining. Casting is generally less expensive and allows for complex internal geometries, such as hollow spokes or integrated brake cooling ducts. However, cast aluminum can have a slightly lower ultimate tensile strength compared to forged material, and the grain structure is not as tightly aligned. Nashville Performance uses cast blanks primarily for their performance-oriented street wheels, where cost and design flexibility are prioritized over absolute strength.

Forging

Forging involves heating a solid billet of aluminum and then applying immense hydraulic pressure—often exceeding 10,000 tons—to reshape the metal. This process creates a dense, continuous grain flow that follows the wheel's contours, resulting in a significantly stronger and more fatigue-resistant product. Forged wheels can be up to 20-30% lighter than their cast counterparts for the same load rating. Nashville Performance reserves forging for their premium track-day and racing wheels, where every gram and every ounce of structural integrity matters. The trade-off is higher raw material and tooling costs, but the end result is a wheel that can withstand extreme lateral loads and repeated thermal cycling without failure.

The CNC Machining Process

The heart of Nashville Performance's manufacturing is CNC (Computer Numerical Control) machining. Whether the blank is cast or forged, it arrives at the machine shop as a rough cylinder approximately the size of a finished wheel plus machining allowance. Multi-axis CNC milling centers—typically 5-axis or 6-axis machines—then systematically carve the wheel into its final shape. The process is divided into several distinct phases:

Rough Machining

Using large-diameter carbide inserts and high-speed spindles (10,000–20,000 RPM), the CNC machine removes the majority of excess material. Toolpaths are optimized to minimize cutting time while maintaining chip evacuation efficiency. Coolant is flooded across the cutting zone to control temperature and extend tool life. This stage removes about 70-80% of the material that will ultimately become chips. The resulting rough shape closely resembles the wheel but lacks detailed features.

Semi-Finishing

With the primary mass removed, the machine switches to smaller, more precise cutters—often with ball-nose or bull-nose geometries—to refine the spoke profiles, contour the barrel, and cut the lug-nut seats. The machine moves in multiple axes simultaneously, achieving the compound curves and undercuts that give each wheel its distinctive look. This stage also cuts the center bore and hub mounting surface to tight tolerances (typically within ±0.05 mm).

Finish Machining

For the final pass, Nashville Performance uses ultra-fine finishing cutters and reduced stepover distances to achieve a surface finish of 32 micro-inches Ra or better. All bolt holes are drilled and reamed to exact dimensions, and any decorative chamfers or bevels are added. The machine also cuts the tire bead seats to SAE specifications, ensuring a proper seal. In some designs, pockets are cut for weight reduction or aesthetic purposes. Finish machining is the most time-consuming stage, but it determines the wheel's final appearance and dimensional accuracy.

Deburring and Surface Preparation

After CNC machining, the wheel is carefully deburred by hand and de-burred using automated brushing tools. All sharp edges are rounded to prevent stress risers and to ensure safe tire mounting. The wheel then undergoes a preliminary cleaning with solvent-based degreasers to remove cutting oils and metal fines.

Quality Control and Testing

Nashville Performance's commitment to quality is evident in their multi-stage inspection regimen. Every wheel that leaves the CNC cell must pass a series of rigorous tests.

Dimensional Inspection

A coordinate measuring machine (CMM) or laser scanner verifies the wheel's critical dimensions: bolt circle diameter, center bore, backspacing, and radial runout. Spoke thickness and barrel wall thickness are measured at multiple points. Any deviation outside the tolerance band (±0.1 mm on most features) results in immediate rejection.

Non-Destructive Testing (NDT)

To detect internal flaws that might not be visible externally, the factory uses X-ray and ultrasonic inspection on a sampling basis (typically 100% of forged wheels; a statistical sample of cast wheels). X-ray systems can reveal porosity, cracks, or inclusions within the aluminum. Ultrasonic probes measure material thickness and identify delaminations. Wheels that pass NDT receive a stamped serial number for traceability.

Mechanical Testing

Representative wheels from each production batch undergo destructive and non-destructive mechanical tests. These include:

  • Radial fatigue testing (ASTM B861) – The wheel is loaded to simulate cornering forces and rotated for 1 million cycles without failure.
  • Dynamic cornering fatigue test (SAE J328) – Applies a load that mimics vehicle cornering at high G-forces. Typically run for 100,000 cycles.
  • Impact test – A striker is dropped onto the wheel rim to simulate pothole impacts. The wheel must not crack or leak air.

Any test failure triggers a root cause analysis and may require a design or process change before production can resume.

Finishing and Coating

The final step is protecting the wheel from the elements while giving it a show-quality appearance. Nashville Performance offers several finishing options, each applied after thorough surface preparation.

Powder Coating

Powder coating is the most common finish. The wheel is sandblasted to create a uniform surface profile, then electrostatically charged powder particles are sprayed on. The wheel is cured in an oven at around 400°F (200°C), melting the powder into a durable, chip-resistant layer. Powder coating is available in a wide range of colors—from matte black to custom gloss finishes—and provides excellent UV and corrosion resistance.

Anodizing

For a more metallic look, anodizing is employed. The wheel is immersion-treated in an acid bath and subjected to an electrical current, creating a thick oxide layer that is both wear-resistant and dye-adherent. Anodized finishes are harder than powder coating but offer less impact resistance. Nashville Performance offers clear anodizing to retain the raw aluminum look, as well as black and gold dyed anodizing for a premium aesthetic.

Clear Coat and Paint

Some wheels receive a liquid paint system that includes a primer, color coat, and clear topcoat. This is typically used for multi-color designs or when a super high-gloss finish is desired. The paint is baked in a controlled environment to ensure hardness and longevity.

Final Assembly and Packaging

After coating, the wheels undergo a final visual inspection under bright, shadowless lighting. Any surface defects—such as orange peel, dust nibs, or minor scratches—are recorded and the wheel may be reworked or scrapped. Approved wheels are fitted with valve stems (if required), balanced on a high-speed balancer, and wrapped in protective foam. They are then packed in individual boxes with dividers to prevent contact damage during shipping. Each box includes a certificate of inspection and weight data.

Why CNC Machined Wheels Matter

The combination of precision CAD design, high-quality alloy selection, and advanced CNC machining allows Nashville Performance to deliver wheels that are both lightweight and extremely strong. The ability to hold tight tolerances ensures perfect hub fitment, reducing the risk of vibration and brake rotor runout. For enthusiasts and racers, a CNC machined wheel represents the pinnacle of engineering—where form meets function without compromise. Whether forged for track use or cast for daily driving, every wheel reflects the company’s dedication to manufacturing excellence.

For further reading on wheel engineering standards, refer to the SAE J328 wheel test standard and the ASTM B861 specification for aluminum alloy forgings. To understand the metallurgy of 6061-T6 vs 7075-T6 aluminum, see the ASM Material Data Sheet.