C7

[SVT666]

Probably more a function of chassis rigidity than the type of spring used.  There have been plenty of cars with coil-overs that have been considered twitchy and jittery.

Why hamper yourself by using a transverse leaf spring when it's completely unnecessary?  The leaf spring has the same problem as the live axle (albeit not as severe) with cross-talk.  Here is a good explanation from a racing engineer:

"Cross talk happens whenever the car is in roll, meaning whenever it is in a turn and the body starts to roll over the wheels, compressing the suspension. The symptoms are the spring giving a harsh ride and abrupt transitions from a neutral balance or understeer balance, to an oversteer balance, or vice versa.? Sonnen explains.

Sonnen continues, ?The leaf spring reduces the true independence of the suspension, although it is still technically geometrically independent. Using the see-saw example, you can see that any deflection on one side of the leaf, like when you are in a turn and the car?s body starts to roll and compresses the suspension, will have an adverse effect on the other side of the leaf. Adding to the problem is the rising rate in the transverse leaf spring, meaning more force is required to compress it from, say 2-4 inches of bump, than 0-2 inches of bump. This can contribute to a harsh ride characteristic and tendency for abrupt transitions that Corvettes, and especially C6 Z06s, are known for.?

[Payman]

Okay, but I don't think it's as big a deal as finally getting a good interior, good seats, a good shifter, etc. The leaf spring might be a detriment to hot lap times, but it's not real world noticeable like the live axle on the Mustang.

[MX793]

With the way the Corvette's leaf springs are secured to the chassis, compression of one side of the spring will actually induce compression on the other end, essentially assisting the anti-roll bar (and allowing for a smaller anti-roll bar).  This behavior was intentional.  If they wanted to isolate the sides, they could do so by using independent cantilevered "leafs" for each corner.

[Rich]

With the way the Corvette's leaf springs are secured to the chassis, compression of one side of the spring will actually induce compression on the other end, essentially assisting the anti-roll bar (and allowing for a smaller anti-roll bar).  This behavior was intentional.  If they wanted to isolate the sides, they could do so by using independent cantilevered "leafs" for each corner.

So from an engineering perspective, which is better?  Having the spring act like an anti sway bar, or have two separate entities?

[SVT666]

Okay, but I don't think it's as big a deal as finally getting a good interior, good seats, a good shifter, etc. The leaf spring might be a detriment to hot lap times, but it's not real world noticeable like the live axle on the Mustang.

Speaking as someone who has driven Mustang extensively, including several new ones in varying forms (GT, GT Vert, V6 Vert, etc.) you can't tell it has a live axle, unless you hit a mid corner bump as a high rate of speed.  Ford has done wonders with the live axle.  It handles and performs better than the Camaro SS with full IRS.  I'm just saying, there are better ways of doing things and holding on to this inferior method because "it's good enough" is no excuse.  Same with the Mustang.

[MX793]

So from an engineering perspective, which is better?  Having the spring act like an anti sway bar, or have two separate entities?

Depends on what your design goals are.  There are certainly some packaging advantages offered by the configuration (similar could be said for the torsion beam rear axle).  From an adjustability/tuning standpoint, leafs are far from ideal.  Coil-overs offer better adjustment and that's why the factory Corvette race cars use them in lieu of the road car's leaf springs.

My point was really more that the cross-talk from the Vette's transverse leaf behaves a little differently from that experienced by a live axle design.  And that no car with a sway bar has total independence between left and right sides of the car.

[Payman]

Speaking as someone who has driven Mustang extensively, including several new ones in varying forms (GT, GT Vert, V6 Vert, etc.) you can't tell it has a live axle, unless you hit a mid corner bump as a high rate of speed.  Ford has done wonders with the live axle.  It handles and performs better than the Camaro SS with full IRS.  I'm just saying, there are better ways of doing things and holding on to this inferior method because "it's good enough" is no excuse.  Same with the Mustang.

Drove a '95 Mustang for almost 3 years. The live axle is very apparent, although the latest has been very good apparently.

[2o6]

Drove a '95 Mustang for almost 3 years. The live axle is very apparent, although the latest has been very good apparently.

In some rougher roads, you really are reminded that it is a live axle (axle hop), but for the most part, I too would take a Mustang over a Camaro.

[GoCougs]

With the way the Corvette's leaf springs are secured to the chassis, compression of one side of the spring will actually induce compression on the other end, essentially assisting the anti-roll bar (and allowing for a smaller anti-roll bar).  This behavior was intentional.  If they wanted to isolate the sides, they could do so by using independent cantilevered "leafs" for each corner.

So now you've got two complex independent dynamic suspension elements working in parallel...

[GoCougs]

Chevy uses the transverse leafs for the same reason Ford uses a truck axle in the Mustang and Porsche uses a rear engine in the 911: legacy. No clean sheet design of a competing product will ever have these design elements as they simply under perform and otherwise suck.

[SVT666]

Drove a '95 Mustang for almost 3 years. The live axle is very apparent, although the latest has been very good apparently.

I had a '96 GT for 3 years as well.  It doesn't compare.  Those Mustang were like driving pickups compared the new one.  The new one is so good it makes you question whether it really needs IRS.  That is until you see the ZL1 and 1LE lap times.  I don't know why Chevy didn't get it right on the SS though.

[MX793]

So now you've got two complex independent dynamic suspension elements working in parallel...

How is it appreciably different from a double-wishbone or multilink IRS with an anti-roll bar?  You compress the right side of the suspension and the sway bar pulls the left side up into the car as well.

[GoCougs]

How is it appreciably different from a double-wishbone or multilink IRS with an anti-roll bar?  You compress the right side of the suspension and the sway bar pulls the left side up into the car as well.

The leaf has a (bit of) variable rate. It will also carry a bending load whereas the sway bar will carry a torsional load.

[MX793]

The leaf has a (bit of) variable rate. It will also carry a bending load whereas the sway bar will carry a torsional load.

Variable rate I'll give you.  How does using a torsion spring (sway bar) to link left and right wheels make any appreciable difference in the suspension behavior?  At the end of the day, the wheels aren't truly independent as the movement of one affects the other.

[hotrodalex]

I'll trust GM engineers to know what they're doing and make the right design compromises. Since, you know, the Corvette is one of the best performing cars for the money (and even just in general).

[SVT666]

You trust GM engineers?  Only recently have they shown any intelligence at all.

[Soup DeVille]

You trust GM engineers?  Only recently have they shown any intelligence at all.

GM has always had a lot of top quality engineers- who apparently were completely ignored in all product development meetings and activities, but that doesn't mean they weren't there.

[280Z Turbo]

You trust GM engineers?  Only recently have they shown any intelligence at all.

That's not true.

[SVT666]

That's not true.

Really?  Cause I can list a boat load of cars that backs me up.  I know it wasn't the engineers but the company wouldn't let them do their job.

[MrH]

Where did you get such an intimate knowledge of the operations of GM?! 

[SVT666]

Where did you get such an intimate knowledge of the operations of GM?! 

You're saying I'm wrong?

[GoCougs]

Variable rate I'll give you.  How does using a torsion spring (sway bar) to link left and right wheels make any appreciable difference in the suspension behavior?  At the end of the day, the wheels aren't truly independent as the movement of one affects the other.

True, but a variable rate spring in tandem with a constant rate spring is asking for dynamical issues.

[GoCougs]

I'll trust GM engineers to know what they're doing and make the right design compromises. Since, you know, the Corvette is one of the best performing cars for the money (and even just in general).

And Mustang engineers and 911 engineers know what they're doing too yet...

[MrH]

You're saying I'm wrong?

To put it bluntly, you're just showing how grossly naive you are to what it takes to design a car.

[SVT666]

To put it bluntly, you're just showing how grossly naive you are to what it takes to design a car.

To put it bluntly, GM's problems are well documented about how the beancounters ran the company and wouldn't let the engineers design the cars the way they knew they should be built.  Hell, there was even an editorial about it in one of the magazines two months ago (Motor Trend or Car & Driver or R&T), where the Editor quotes GM engineers about how they were handcuffed.  It's only recently that those handcuffs have been loosened and even removed in some cases (ATS, ZL1, 1LE, Cruze).  Even in the book "American Icon: Alan Mullaly and The Fight to Save Ford", it is talked about how both Ford and GM faced the same problems and how the engineers weren't allowed to design the cars they wanted to design.

EDIT:  November R&T

[sportyaccordy]

Where did you get such an intimate knowledge of the operations of GM?! 

Werent you the dude who claimed GM's problems were solely due to unions

How are you any better informed on how they operated in the past

[sportyaccordy]

True, but a variable rate spring in tandem with a constant rate spring is asking for dynamical issues.

Not if you set it up in MATLAB first

No but seriously like MX said pretty much every car outside of the MP4-12C is a combination of springs. Couple the fact that a coil spring prob has different static preload than a sway bar, its clear the avg car tends to have the very setup you speak of. The best ones don't have any issues. Its all in the setup

[sportyaccordy]

To put it bluntly, GM's problems are well documented about how the beancounters ran the company and wouldn't let the engineers design the cars the way they knew they should be built.  Hell, there was even an editorial about it in one of the magazines two months ago (Motor Trend or Car & Driver or R&T), where the Editor quotes GM engineers about how they were handcuffed.  It's only recently that those handcuffs have been loosened and even removed in some cases (ATS, ZL1, 1LE, Cruze).  Even in the book "American Icon: Alan Mullaly and The Fight to Save Ford", it is talked about how both Ford and GM faced the same problems and how the engineers weren't allowed to design the cars they wanted to design.

Dude spends a year in the automotive supply chain and now he's Bob Lutz

The cocky second coming of that dude w/the ratty Impreza wagon

[MrH]

Werent you the dude who claimed GM's problems were solely due to unions

How are you any better informed on how they operated in the past

You want to show me where I said GM's problems were solely due to unions?

You've got a terrible memory.

[MrH]

Dude spends a year in the automotive supply chain and now he's Bob Lutz

The cocky second coming of that dude w/the ratty Impreza wagon

No, not at all.  I'm just smart enough to know that I don't know everything. Making definitive statements like "GM does nothing smart and their engineers are completely handcuffed" is the pinnacle of arrogance.  GM's engineers certainly have always had a say in the how things are designed, and no company lets the engineers go wild.  It's a fine balance and not nearly as black and white as Craig suggests.