Cast vs Forged Rims

[JHZR2]

MB back in the day specified forged alloy wheels only. This was for strength and I suppose longevity. Several aftermarket versions of the bunt wheel came out after, German TUV approved, but not forged, rather cast alloy.

Some of these wheels are verging upon 40 years old. At least the OE ones...

Has casting/forging technology of non super-fancy racing wheels changed much in 40 yrs?

Is there a practical difference between cast and forged wheels, especially if carrying a TUV quality Rating and used on a highway driven car?

Aren't most cars' alloys just cast?

Thanks!

 

[Quattro Pete]

From what I understand, most alloys are cast because it's cheaper to make. The problem is that a strong alloy wheel will tend to be fairly heavy. On the street, it may not matter. But in racing, you'll see forged wheels being used more because they can be made strong while still being light. That carries a hefty price tag though.

 

[JosephHarmon]

Forged wheels will be very expensive. They will be very lightweight and usually modular. They are more likely to bend some before cracking while a casting will be very brittle.

 

[JHZR2]

All OE Mb wheels were forged though... Not that MBs in the 70s and 80s weren't very expensive... They've cheapened them since... of course.

 

[jaj]

The modern cast-vs-forged debate is not about strength, it's about whether they bend or fracture under extreme stress. Forged wheels have a higher yield strength than cast, but they aren't more rigid or stronger in any sense in day to day use.

I suspect back in the day when the bundts were modern, cast wheel quality was much more variable. That was when MB put a wear sensor in every brake pad, so cost really wasn't a driving factor in the engineering choice.

 

[rclint]

Applications vary in the need of cast verses forged in any application. I can't imagine why a road car/passenger car would call out a forged wheel instead of a cast wheel, I don't think longevity has to do with either..

Are the forged wheels on MB aluminum or steel ? I assume aluminum, which would mean they purchased wheels in billets and turned/mill work on a CNC (5 axis?) anyway I watched a show on them building race car wheels, the steel wheels they built were nothing exceptional two flat pieces of steel and they used hydraulic pressure to form the wheels, and cleaned up the bolt holes at the end... or maybe they punched them I can't remember on the holes, but I do remember it was a two piece wheel welded together. You may be able to catch it online "How it's made" I'm 99% sure was the show.

 

[JHZR2]

Forged aluminum. The FSM calls them forged light alloy...

 

[gomes512]

I was always under the impression that forging "compacts" the metal meaning less porosity and inclusions.


But anyways here is an interesting document:
http://www.esi-group.com/products/casting/Etips/e-tips/eTip16.pdf

 

[CapriRacer]

There is so much involved in this that it is imposssible to sort out.

Obviously if all things were the same, forged wheels would be better - but who is to say that all things are the same.

 

[JHZR2]

Well I have to assume that a classic MB forged rim is about the pinnacle of quality.

Question is if a similarly aged aftermarket cast rim of identical style gives anything up...

 

[CapriRacer]

Originally Posted By: JHZR2
Well I have to assume that a classic MB forged rim is about the pinnacle of quality.

Question is if a similarly aged aftermarket cast rim of identical style gives anything up...


OK, the theory says that forging does 2 things - work hardening, and grain direction.

So a "all other things being equal" cast wheel will be heavier - and I think that's the only thing you can be sure about.

But like I said,, there is so much involved, I don't think you will find a "all other things being equal" type of situation.

 

[SteveSRT8]

Don't assume anything about MB quality. I broke a rim on a 240d way back when, just hit a curb. I've done worse in a heavy truck and never broke a rim! This was on factory alloys in both vehicles.

Quality varies tremendously by manufacturer. You can't just say "all cast is junk" or "all forged are better". At least if you get OEM wheels they passed a lot of testing.

The aftermarket is a [censored] shoot.

 

[JHZR2]

Originally Posted By: SteveSRT8
Don't assume anything about MB quality. I broke a rim on a 240d way back when, just hit a curb. I've done worse in a heavy truck and never broke a rim! This was on factory alloys in both vehicles.

Quality varies tremendously by manufacturer. You can't just say "all cast is junk" or "all forged are better". At least if you get OEM wheels they passed a lot of testing.

The aftermarket is a [censored] shoot.


Probably a 5.5 x 14" alloy wheel that looks like it takes a hubcap... looks like a steelie?

They are known to be weak...