[WhyUMad1LE]

One of the most important specifications in modern performance cars is torsional stiffness. The Camaro team has been attentive to this by using the already advanced Alpha platform from the ATS along with various bracing packages depending on the model. I haven't seen any hard numbers released though.

It would be nice to know the global static torsion in N-m/deg for the various models. Just from driving mine I am sure they will be impressive figures. Thanks.

[vtirocz]

Good question. I’d like to see both torsional and bending stiffness data compared to prior generations.

[DGthe3]

I'm curious on this one. Getting 'behind the scenes' engineering info is kinda what this section is about afterall.

[Norm Peterson]

I've seen some torsional and bending stiffness-related numbers for the 5th gen, except that they were in Hz instead of lb/in or in*lb/deg.

18 Hz (torsional, dynamic), 21 Hz (bending, dynamic), referenced back to wardsauto.com from a compilation of car body stiffnesses.

If this question gets picked and the answer is also provided in Hz, it'd be nice if a correlation from frequency units to stiffness units could be provided as well.


Norm

[ninetres]

These numbers would mean nothing to me :whoknows:

In all my years as an auto enthusiast, never once have I overheard a discussion around actual chassis stiffness data. I think we already know the Alpha is stiffer....but learning the hertz numbers or whatever must only be interesting to engineers.

If we learned the alpha is 37.42% stiffer would it be some amazing discovery? Not to me.

[Camaro Dude]

Actuuuualy, Hz chassis rigidity talk was taken quite seriously in VW/Audi forums of yesteryear, even BMW forums that I was involved in a few years back.

German car owners (like myself), took their chassis rigidity numbers very seriously lol

If you want some food for thought, and also how old this topic really is in the modern car day world, read about the VW Pheatons Flag Pole Test.

This goes to show how far behind Made_In_USA cars really were, but finally caught up circa 2010.

[ninetres]

Originally Posted by Camaro Dude

Actuuuualy, Hz chassis rigidity talk was taken quite seriously in VW/Audi, even BMW forums that I was involved in a few years back.

German car owners (like myself), took their chassis rigidity numbers very seriously lol

If you want some food for thought, and also how old this topic really is in the modern car day world, read about the VW Pheatons Flag Pole Test.

This goes to show how far behind made_in_USA cars really were, but finally caught up circa 2010.

That’s crazy. Learn something new everyday. I’m just one guy....so not exactly a large sample size. But I would have figured in the 20-odd years I’ve been a gear head drag racing, half mile racing, and time attacking I would have stumbled into a conversation like this if it’s somewhat common in the scene.

[Norm Peterson]

Originally Posted by ninetres

That’s crazy. Learn something new everyday. I’m just one guy....so not exactly a large sample size. But I would have figured in the 20-odd years I’ve been a gear head drag racing, half mile racing, and time attacking I would have stumbled into a conversation like this if it’s somewhat common in the scene.

I doubt that very many drag racers or half-milers pay much attention to chassis stiffness, and if there are any that do they're keeping it quiet as a competitive advantage. As a serious time-attack competitor might do as well.

Yes, it is something that takes at least an engineering outlook for it to be very useful. And it makes more sense when (as an engineer) you're aware that every piece of structure and every mechanical component is some kind of spring when it comes down to following loads and load paths. For a car's chassis, in overview it's just the one big spring connecting the front and rear suspensions as springs. Among other things its stiffness determines in large part how effective any given suspension tweak is at shifting the distribution of lateral load transfer (i.e. how effectively you can shift the handling balance with things like specific bar adjustments and spring changes).

It's also something that's subject to diminishing returns, so there's probably some practical limit (perhaps some multiple of suspension roll stiffnesses or a multiple of the difference between front and rear roll stiffnesses?). And I think that sometimes the 'diminishing returns' aspect goes unrecognized in the chase for still bigger numbers for the sake of having big numbers.

I have a few comparisons that might be of specific interest here. Except as noted, values are in units of Nm/deg (Newton*meters/deg). Divide them by 1.355 for ft*lb/deg numbers. It should be apparent why I'd like to see the relationship between frequency and stiffness.

Chevrolet
Chevrolet Camaro Convertible (2011 – 2015) 18 Hz (torsional, dynamic), 21 Hz (bending, dynamic) Link
Chevrolet Cobalt 19,300
Chevrolet Corvette C5 9,100
Chevrolet Corvette C7 (2014 – ) 14,500
Chevrolet Cruze 17,660
Chevrolet Malibu (8th-gen, 2013 – 2016) 23,000 (w/o moonroof)
Chevrolet Malibu (9th-gen, 2016 -) 23,600 (w moonroof)

Ford
Ford Fiesta 3-door (3rd gen, 1989 – 1997) 6,500
Ford Focus 3-door 19,600
Ford Focus 5-door 17,900
Ford Fusion (2010 – 2012) 17,453 (1,000 kNm/rad) Link
Ford Fusion (2013 – ) 19,286 (1,105 kNm/rad) LinkFull document part 1part 2
Ford GT 27,100
Ford GT40 MkI 17,000
Ford Maverick 4,400
Ford Mustang 2003 16,000
Ford Mustang 2005 21,000 . . . . (15,500 ft*lb/deg approximately)
Ford Mustang Convertible (2003) 4,800
Ford Mustang Convertible (2005) 9,500

Norm

[WhyUMad1LE]

Attached is a slideshow about the structures of ATS and CTS.

Interesting that adding a sunroof to the CTS drops the stiffness by 2100 N-m/deg!

[Norm Peterson]

Thanks for the [downloadable] link.

I'm not at all surprised at the stiffness loss, or its magnitude.


Norm

[WhyUMad1LE]

I knew there would be a loss but didn't think it would be that significant.

Just checked and the CTS sunroof is panoramic so it makes sense now.

[Norm Peterson]

When you cut a fairly wide, fairly long hole out of the roof panel, it loses a lot of stiffness as a shear panel. You still have a little shear stiffness (from the pieces that are left), and the roof's frame is still there, but beams in shear + bending aren't as rigid as short deep panels in shear as long as the panels don't buckle. I imagine that reinforcement gets added, but you can't make that as effective as what you cut out either. Stronger locally so that you don't get fatigue cracking with use, sure. But strength isn't necessarily a direct indication of stiffness either.


Norm

[HyperspaceTurd]

Where can I get an X-brace?