Forged, cast or flow formed: what you get for the same budget

A cast wheel is made by pouring molten aluminium into a mould; a flow formed wheel keeps a cast centre, but its barrel, the part that carries the tyre, is rolled hot over a mandrel; a forged wheel is shaped in the solid state under a press, then machined. The usual forged alloy is not lighter per cubic centimetre than the cast alloy, but its yield strength is higher (270 against 200 MPa), which allows less material to be used for the same strength. A retailer puts a set of four, all diameters, at €300 to €1,200 cast, €600 to €1,600 flow formed and €1,400 to more than €4,000 forged; our forged 20-inch sets cost €3,300 in monoblock and €4,400 in two-piece, including 20% VAT for delivery to mainland France (in Great Britain, £3,440.40 and £4,586.40 with UK import VAT).

The three processes in one table

The alloy values are typical values from the MakeItFrom database, for A356.0-T6 and 6061-T6. They are material values, not measurements taken on a wheel, nor guaranteed values. The forging defect is described by Wikipedia, “Forgeage”, in French. The price ranges are those published by the retailer 1max2fun for German and Italian brands, excluding tyres and fitting; specific offers are compared further down and on our price page.

The cast wheel

Molten aluminium fills a mould, then solidifies. Low-pressure casting in A356 alloy is one of the ways production wheels are made. An industrial study published in 2020 in the journal Metals describes the process.

The defect this process must control is shrinkage porosity. Shrinkage cavities (Wikipedia, in French) are voids left by the metal shrinking as it solidifies. The same study measured the size and location of this porosity in wheels from production, depending on the temperature of the mould.

What you get: the design and dimensions of the catalogue, in the lowest price range of the three processes.

The flow formed wheel

The starting point is a cast wheel. Mounted on a mandrel, it turns while a burner heats the barrel and a roller presses and stretches the metal to form the barrel. Yamaha describes this process for its SpinForged wheels. Enkei presents its MAT process as the combination of a one-piece cast wheel and a barrel formed by spinning (Enkei).

The centre, that is the spokes and the hub, therefore remains a cast part. Only the barrel is worked. The makers who use this process state that the barrel is stronger. We have not found public values that can be compared from one maker to another, and we do not invent any.

What you get: often a catalogue design, sometimes with an offset or a PCD machined on request. For example, for the Concaver CVR6 in 20×9, an offset from 21 to 51, charged at €20 more per wheel, and a PCD from 108 to 130 mm (BPS Racing).

The forged wheel

Forging shapes the metal in the solid state. It replaces the solidification structure with a fibrous structure, which improves the mechanical properties in the direction of deformation. It does not give shapes as complex as casting: the design of the wheel comes from machining. It also has its own defect to control: after forging, the part must be cooled in a controlled way to avoid surface cracks, known as quench cracks (Wikipedia, “Forgeage”, in French).

For our wheels, a block of 6061-T6 aluminium is forged, then 5-axis CNC machined to your vehicle's measurements. The steps, from agreeing the measurements to delivery, are set out on our lead time page.

Forged wheels come in three constructions:

• the monoblock, from a single block;
• the two-piece, a forged centre and a barrel joined together;
• the three-piece, a centre held between an outer barrel and an inner barrel.

What you get: depending on the seller, a catalogue design in the dimensions chosen, or wheels whose width, offset, PCD and centre bore are made to measure.

What the alloy figures say

• Density is not what makes a wheel light. 6061-T6 (2.7 g/cm³) is not lighter per cubic centimetre than A356-T6 (2.6 g/cm³). A forged wheel weighs less when it contains less material.
• A higher yield strength means less material is needed. 270 MPa against 200 MPa: 6061-T6 withstands 35% more stress before it deforms permanently. For the same load, the sections can be thinner.
• Elongation tells you how the part gives way. 10% against 6%: 6061-T6 deforms more before it breaks.
• In fatigue, the two alloys are close: 96 MPa against 90 MPa. Between two wheels, the difference then comes from the design, the thicknesses and internal defects, such as the shrinkage porosity of casting.

Weight: no single percentage

You often read that a forged wheel weighs a certain percentage less than a cast wheel. We do not publish a single percentage. The difference depends on the diameter, the width and the design of the spokes, and a single figure would be wrong for most wheels.

To compare, ask for the weight of one wheel, at the same diameter and width, for the models you are hesitating between.

For the same budget, which to choose?

The retailer's ranges, then specific 20-inch offers, taken on 3 October 2026:

For Great Britain, our checkout charges in pounds sterling. It converts the euro price at its exchange rate on the day, currency conversion charge included, so the amount in pounds is about 2% more than a straight conversion at the market rate; the amount shown at checkout is the one charged for your order. The amounts in pounds on this page are those of 4 October 2026. Delivery is included in the price, so UK import VAT (20%) applies to the whole amount in pounds. The carrier collects the VAT before delivery, together with its clearance fee (for example, DHL Express charges £11 or 2.5% of the duty and VAT it pays, whichever is higher) and any import duty. Any import duty depends on the UK tariff in force when your wheels arrive: the amount you pay is the one on the carrier's notice, and UK import VAT then applies to it too. The details are on our Delivery to Great Britain page.

These benchmarks overlap. Between €1,400 and €1,600, the flow formed and forged ranges overlap. The flow formed set found in 20-inch (€2,559.96) costs more than the retailer's range for that process, and more than the lower end of forged. The process alone therefore does not set the price: the brand, the diameter, the width, the options and the terms of sale count too. The terms of each offer (measurements, render, lead time, warranty) are compared on our price page.

Our reading:

• If the catalogue design suits you and the wheels are for road use, a cast or flow formed wheel from an established brand meets the need for less. Check that its tyre size is intended for your vehicle: see roadworthiness test and registration.
• Forged makes sense when you want exact measurements (width, offset), a precise design or finish, or less material for the same strength.
• It takes a lead time: 4 to 8 working weeks, shipping included, for our wheels.
• The two-piece costs more than the monoblock at the same diameter. It widens the range of widths and offsets, and its lip depth can be adjusted (two-piece). The three-piece is priced on quotation (three-piece).

Before paying for a forged set, compare sellers on what they write: alloy, process, measurements, lead time, warranty, invoice. That is what the 12 checks before choosing a maker are for. To price a project: the configurator.

Sources

• MakeItFrom, A356.0-T6 and 6061-T6: density, tensile strength, yield strength, elongation, fatigue strength (typical values).
• Metals, 2020, 10(5), 563: low-pressure casting of A356 wheels, shrinkage porosity.
• Wikipedia, “Défaut de moulage”, section on shrinkage cavities, and “Forgeage”, in French: fibrous structure, quench cracks.
• Yamaha Motor, SpinForged Wheels and Enkei, MAT process: flow forming described by those who use it.
• Prices: 1max2fun, BPS Racing, Forza Performance, Autojantes, and our price list.

All these pages were accessed on 3 October 2026.

Written by the Onyx Forged design office. Updated on 24 October 2026.