Forged vs cast rims

[Chevelle3221]

Forged vs cast wheels. Which is better and why? Thanks

 

[Vercingetorix]

Real forged wheels are always better. Probably 2k a pop though.

 

[DuckRyder]

Forged are generally lighter an stronger... with a corresponding price adjustment.

Better for what and is the cast good enough for the application...

 

[Marcozi]

"Forged" means that the wheel started as a hunk of alloy, likely in the shape of a wheel. The manufacturer then uses a computer numerically controlled (CNC) machine to machine off the unwanted alloy. "Cast" means the manufacturer filled a wheel cast or mold with molten alloy. The surfaces of the resulting "wheel" are machined by a CMC machine.

 

[CleverUserName]

Forged vs cast wheels. Which is better and why? Thanks

Forged wheels can be made with less material because the aluminum is more dense and stronger. They are very light, typically 20%+ lighter than a cast wheel of the same size. An alternative is a rolled or flow formed wheel. The barrel is rolled in a press which hardens it and the spokes are cast aluminum.

"Forged" means that the wheel started as a hunk of alloy, likely in the shape of a wheel. The manufacturer then uses a computer numerically controlled (CNC) machine to machine off the unwanted alloy. "Cast" means the manufacturer filled a wheel cast or mold with molten alloy. The surfaces of the resulting "wheel" are machined by a CMC machine.

A cast wheel can be forged. It would need to be heat treated after casting to be 6061 or 7075 forged aluminum. The shape and design of the wheel can be created by milling the casting prior to heat treatment. All ar15 receiver are made this way.

A billet wheel would be machined from a solid forging of 6061/7075.

 

[Mainia]

The lighter wheels get you less rotating mass and less unsprung weight. This in turn lets the suspension/tires follow the road's surface better because it lets your suspension react faster to movements. And reducing rotating mass aids in increasing engine response and increases what you would "feel" as an increase of HP/TQ, as it takes less of both to move the same distance. You can feel this in your butt dyno.

I can feel a tangible difference when changing my "winter" OEM cast rims/tires for my "summer" aftermarket wider/rotary forged rims/tires. My car is more nimble in the corners and responds better to steering inputs and patched pothole shudder bumps while cornering with the lighter rims. Also I feel the difference on how the car accelerates too. If I had the money to go to the next level of weight reduction, I would love to get lightened two piece brake rotors and aluminum calipers for adding even more of and advantages of unsprung/reduce rotational mass, but that will never happen.

 

[y_p_w]

"Forged" means that the wheel started as a hunk of alloy, likely in the shape of a wheel. The manufacturer then uses a computer numerically controlled (CNC) machine to machine off the unwanted alloy. "Cast" means the manufacturer filled a wheel cast or mold with molten alloy. The surfaces of the resulting "wheel" are machined by a CMC machine.

Removing material isn't forging per se. And most wheels called "forged" would be cold forged at anywhere from room temp to even colder temps. It has to be done in a way that presses/deforms the remaining material at a relatively cold temperature, although I suppose some of these processes do end up removing material. There are CNC machining processes that don't actually deform the original material, but just shave it off. I believe there are ways to forge a material with minimal removal of the underlying materials. There might also be post-forging machining to get the piece into a precise shape. I've had cast wheels that had clear machining marks.

Deforming metal causes strain hardening, which makes it stronger. I remember a demonstration done in my materials science class. The prof would take out an annealed copper rod that was maybe 3/4" diameter. He got a bit of criticism over the years for it, but he would look in the class for a really small student - usually a woman. Then he would ask this student to bend the rod, which was actually quite easy because it was soft and annealed. Then he looked around for a student in the class who had big arms. For my class he found a guy who looked like he spent hours in the gym every day and looked like he could have been a football player. Then he asked this student to straighten it out and he just tried and tried but couldn't do it. Once it was deformed, it resisted any further deformation unless it was annealed. The crystal structure of the copper was changed due to the deformation. It's more or less what happens with a soft metal (aluminum or copper) gasket, although it doesn't rebound like rubber or most plastics.

I found a pretty good explanation here.

https://interplex.com/cold-forging-guide/

 

[y_p_w]

Forged wheels can be made with less material because the aluminum is more dense and stronger. They are very light, typically 20%+ lighter than a cast wheel of the same size. An alternative is a rolled or flow formed wheel. The barrel is rolled in a press which hardens it and the spokes are cast aluminum.

Uh no. Forging doesn't make a metal/alloy more dense. It's not compressing metal. At a microscopic level it's probably less dense because of point defects, but not in any appreciable numbers.

Less overall material can be used because the metal is work hardened and thus stronger.

 

[Chevelle3221]

Thanks