What is the difference between forged aluminum wheels and cast aluminum wheels? Which is better and why?

 

I would like to hear everyone's input on this one. From what I understand, forged is suppose to be better. I should know, I own 4 of them, came on '02 convertible. I just replaced all 4 because they are cracked where the spokes meet the outer rim. NOW lets here it!!!!

 

Forged are stronger and lighter, but more expensive.

Cast are cheaper, but heavier.

Caveat: Normally.

I prefer to keep my wheel/tire combo as light as possible, unsprung weight has a massive effect on suspension performance and acceleration. Though I also have no desire to spend 5k+ on a set of these "uber" wheels that some companies sell.
I've been told by a respectable tuner that HRE wheels were a waste of money because they tend to be heavier then their (most of the time) cheaper, alternatives. When I buy nice wheels, they will be CCWs, as they seem to be the lightest high end wheels.

 

Forged did not come on 02, they were spun cast as far as I know. The 01 Z06 wheels were cast by Alcoa, they are stronger and slightly heavier than the cast version that followed in 02.

 

The RPO# QF5 wheels, that were optional on my 01, were listed as forged aluminum wheels. They will crack too!

 

The difference between forged and cast is that forged wheels are lighter because you can use less metal to construct the wheel because the forging, which is in essence a method of pounding the particles together to make a tighter structure, is stronger. The cast is molten metal poured into a form which cools naturally, therefore the metal is not as dense. The drawback of forging is that with enough force it will crack because of the rigidity of the metal. However, even though cast wheels might be heavier, castings do have a little give. They can actually bend a little before breaking and sometimes can be straightened. Over the years I've seen plenty of bent cast wheels at dealers I've doen work for. You can bend and straighten a wheel lip on a cast wheel. I've got CCW Classics on my car and fortunately they are modular. I had a serious lip bend and I was able to replace the damaged part instead of junking the whole wheel.

 

To the best of my knowledge, this statment is wrong! My '02 vert came with Alcoa 5 spoke polished thinspokes. Maybe someone with more knowledge than I can get in on this subject. I would appreciate hearing it. Thanks!

 

I think the confusion is Z06 wheels versus coupe/convert wheels ....

Z06 wheels

2001 - FORGED aluminum wheels made by ALCOA
2002-2004 - SPUN CAST aluminum wheels made by Speedline

Note that the spun cast wheels, exactly the same size as the forged wheels, are about 1.5 pounds per wheel lighter than the forged wheels.

Coupe/convertible

Several different wheel options have been offered during the life of the C5 .... QD4, QF5, etc. .... as far as I know ALL are FORGED aluminum, some painted, some polished. The ONLY exception was RPO N73 which are magnesium. They were mostly shipped for export .... but could be ordered for a domestic car.

 

Forging is a method of heating and pressing ,with extreme pressure a piece of metal into the desired shape. Metal has grains that run through it sort of like the rings in a tree and when pressed into shape these grains follow the contours of the metal. Think of it this way ,a branch of a tree grows and is obstructed by a fence or whatever it grows into a straight piece with a "c" shaped piece in the middle, now take a piece of lumber put it on a lathe and machine it to the same shape,which one breaks first? Casting has come a long way used to be melted metal was poured into a form and allowed to cool problem was inconsistency of the density of the metal to make up for that they usually added more metal to make up for that shortcoming also impurities were present and the hardness would vary throughout the piece and some pieces were porus.They now use vacuumn cast techniques which addresses most if not all if not all of the casting's shortcomings,basically they apply a vacuum to the mold then introduce the melted metal,it eliminates air pockets and makes for a tighter grain structure,but is still heavier than forged.Which is stronger? forged is generally believed to be stronger (think of crankshaft's forged or cast) but they are so close in all areas I would be comfortable using either for wheels.As for repairability I personally would not use a repaired wheel if it took a hit hard enough to need repair the integrity of the wheel is compromised but many have been repaired with no problems. Then there are billet wheels ,but you better get a wheelbarrow and fill it with $$$$ for a set of them.Just my $.02

 

this is what is involved in forging a wheel, there are a few steps not shown, but you get the idea

http://www.aluminumprecision.com/for...l-process.html

john

 

Funny, why wouldn't you just put a question like this in a search engine directly?

Forging and casting are ancient technolgies, you can't forge every shape, casting allows for complex shapes (like engine blocks) but is susptible to cracking easily since it's brittle. Forgings will typically bend before failing/cracking.

 

I agree, but I'de like add castings generally hold their shape better and don't go away(break)(bend) but when they do the part is usually ruined as said prior casting is more brittle.Forged more elastic will bend before breaking/cracking.I've seen a number of cast cranks crack/break but the forged cranks bend,you always get a warning before a forged part breaks .cast breaks all at once

 

Thanks for the education, guys!!