Cast Aluminium
The simplest type of casting is called Gravity casting and is done by pouring molten aluminum into a mold and letting it spread, harden and set.
Low pressure casting is a slightly better process, whereby the aluminum is forced into the mold and set with vacuum pressure, where helps to eliminate those air pockets and increase structural integrity. While cast wheels can be quite strong, they are also heavy, making them not optimal for performance.
Flow-Forming
“Flow-forming” (also known as “roll-forging” and “spun-rim manufacturing”) starts out similarly to low pressure casting. But instead of letting the allow fully set, it is finished by using high-heat, high-pressure spinning steel rollers to create the finalize the outer hoops and the wheel’s shape. The result is a wheel that is nearly as strong as a forged.
Forging
Forged wheels are the true top-of-the-line when it comes to manufacturing process, thus also used on high performance cars from factory. They start as a solid block of billet aluminum, which then has heat and pressure applied until it forms the shape of a wheel and gets finally CNC machined.
This process makes forged wheels incredibly dense, while still allowing them to be 25-30% lighter than cast wheels, despite three times the strength. The forging process allows for more strength with less materials, which means additional room for things like larger brake components.
Cast wheels can be up to 4.5kg heavier in the same design and dimension compared to a forged wheel. Straight line performance gains, due to the fact, that less energy is needed to accellerate the wheels as these are working like an energy storage absorbing the kinetic energy.
And now?
What do we recommend, from the design point of view already the old latins used to say "De gustibus non est disputandum" which roughly translates into don't argue about taste, but you might spot that we got a flair for not doing things like everyone is used to and even if these are the small differences that have us always set apart. We like to have a very technical approach to everything what we do, so form follows mainly function but with distinct details that have been copied over the years, which makes us happy as it confirms what we are doing is the right thing.
The Delta HF integrale is a Lady which had already seen it's best years going by, compared to current production cars, one of the major downsides can be clearly identified in the somewhat weak chassis, which from our personal expierence isn't a problem when the cars is not driven every day like on a Rally Special Stage and with "Neckbreaker" suspension setups and also with heavy wheels.humps and bumps. The Delta can take advantage of the right wheels and suspension setup.
So lightweight is the way to go, many reproduction wheels which are on the low price side can weigh in as much as 13.5kg and more per wheel in 8x17, so this is something we focalize when we choose wheels for our customers. Having savings up to 4kg per wheel in the same size is not uncommon. Especially forged wheels with the extremly lightweight rim barrel section will have further advantage, as the mass needs to be always as close to the center of rotation as possible. Imagine a wheel to be a mass storage, that before it moves needs to be loaded with energy, the heavier it is the more energy it will be capable to store, this before everything else starts to move and the same the other way around.