The Ford Fusion is Motor Trend magazine's car of the year

[GoCougs]

Yes, lateral stiffness is a major issue with leaf springs, as is unsprung weight, wheel travel, packaging, and sufficiently wide range of variable rate.

[2o6]

Why don't all cars use independent suspension?

[the Teuton]

Why don't all cars use independent suspension?

A beam axle can act as an anti-roll bar. For cheap cars, it also keeps costs down without hurting maneuverability too much. Why not keep them on cars that don't need anything more advanced?

[280Z Turbo]

Why don't all cars use independent suspension?

Camber change when the suspension is loaded is undesirable.

[280Z Turbo]

Maybe on a Model T; but things did get a bit better afterwards.

What do you mean? Unwanted movement is the number 1 problem with an axle located with leaf springs. That's why drag racers use ladder bars and multilink setups.

[GoCougs]

Why don't all cars use independent suspension?

With a FWD chassis at least, the transmission and differential are one and the same plus we know that the engine bolts to the transmission; so in effect to have a non-independent FWD chassis, the engine, transmission and differential would have to act as a suspension member. This would not be good on all sorts of levels, plus it'd probably cost more.

[MX793]

A beam axle can act as an anti-roll bar. For cheap cars, it also keeps costs down without hurting maneuverability too much. Why not keep them on cars that don't need anything more advanced?

Torsion beam is different from a live/dead beam axle.  A torsion beam rear suspension is not a beam axle (as the beam does not run along the axle) and it is not non-independant.  It's technically classed as an independant suspension since the left and rear wheels can move independantly (although "semi-independant" might be a more appropriate name for it).

[68_427]

With leaf springs the wheels also move for and aft a little bit while spring are being compressed.

[MX793]

With leaf springs the wheels also move for and aft a little bit while spring are being compressed.

Same could be said of a trailing or semi-trailing arm suspension.  Or just about any motorcycle suspension or many airbag suspensions in heavy trucks (possibly some cars as well).

[FoMoJo]

What do you mean? Unwanted movement is the number 1 problem with an axle located with leaf springs. That's why drag racers use ladder bars and multilink setups.

I just meant that their was a bit more to securing a live axle than leaf springs, as per this image of the 2010 Mustang...



Even with leaf springs there is, at least a Panhard rod to keep the axle from shifting.

[Nethead]

There is an engineering term used to describe a phenomenom that is one of the chief reasons racecars replaced leaf springs with coil springs.  A coil spring can return an axle to its original position much, much faster than either longitudinal leaf springs or transverse leaf springs.  Carroll Shelby insisted upon replacing the transverse leaf springs in the Cobra with coil springs when the decision was made to replace the 289 with the 427 for this reason.  If a track irregularity deflects an axle (or half-shaft, if you will) suspended by coil springs, the coil springs will return the axle to its pre-deflected position much faster than leaf springs.  We're talking tiny fractions of a second, but racecars and many street cars can travel a very long distance in a tiny fraction of a second--at 205 MPH, for example, a vehicle covers more than the length of a football field every second.  That's over twenty yards in a fifth of a second, which is a very short period of time but would be a long distance to have a tire out of full contact with the road surface.  The engineering term is not "recovery speed" but that's essentially what it is in practical application--how quickly a spring can return a displaced axle/half-shaft to its original position.  It is one reason why some leaf-springed vehicles get squirrelly as they approach their cornering limits.  Aerodynamics and other factors are involved at high speed, too, but there it is...

[Raza]

That thing uses leaf springs, right?

[Eye of the Tiger]

one sideways

[280Z Turbo]

I just meant that their was a bit more to securing a live axle than leaf springs, as per this image of the 2010 Mustang...



Even with leaf springs there is, at least a Panhard rod to keep the axle from shifting.

Huh?

The Mustang uses a multilink coil spring setup. That is not the leaf spring setup that I'm talking about.

I've never seen a panhard rod on a standard leaf sprung axle. Every truck rear suspension I've seen has used two leaf springs to locate the axle.

[Eye of the Tiger]

Huh?

The Mustang uses a multilink coil spring setup. That is not the leaf spring setup that I'm talking about.

I've never seen a panhard rod on a standard leaf sprung axle. Every truck rear suspension I've seen has used two leaf springs to locate the axle.

Slapper bars!

[GoCougs]

That thing uses leaf springs, right?

Had it not been a legacy dating back to the 1963 C2 it would not exist today.

Betcha the C7 does not use leaf springs...

[280Z Turbo]

Had it not been a legacy dating back to the 1963 C2 it would not exist today.

Betcha the C7 does not use leaf springs...

The C2 uses coil springs in the front. The C6 uses a transverse leaf in the front.

Are you suggesting that GM decided to go backwards just to make the car worse?

[GoCougs]

The C2 uses coil springs in the front. The C6 uses a transverse leaf in the front.

Are you suggesting that GM decided to go backwards just to make the car worse?

There would absolutely be no leaf spring transverse or otherwise in the C6 had it not been in the Corvette since 1963.

[MX793]

There would absolutely be no leaf spring transverse or otherwise in the C6 had it not been in the Corvette since 1963.

Yes, and the Impala would not be RWD had it not been RWD since 195... oh wait, nevermind.

[280Z Turbo]

There would absolutely be no leaf spring transverse or otherwise in the C6 had it not been in the Corvette since 1963.

Shouldn't it just have the leaf spring in the back then? Why doesn't it still use coil springs in the front?

[Eye of the Tiger]

I'm going to put slapper bars on the Swift. 

[GoCougs]

Yes, and the Impala would not be RWD had it not been RWD since 195... oh wait, nevermind.

Yet the Impala's stable mate over the years, the Caprice, has always been RWD no matter where it pops up...

The 911 today would never, ever be rear-engined had it not started that way decades ago. It's an inherently flawed design that no other automaker today would ever attempt - not even Porsche.

[GoCougs]

Shouldn't it just have the leaf spring in the back then? Why doesn't it still use coil springs in the front?

Economies of scale I imagine.

[MX793]

Yet the Impala's stable mate over the years, the Caprice, has always been RWD no matter where it pops up...

The 911 today would never, ever be rear-engined had it not started that way decades ago. It's an inherently flawed design that no other automaker today would ever attempt - not even Porsche.

The RR configuration of the 911 is a bit different from leaf springs on the Vette.  The driveline configuration is a defining trait of the 911.  It's responsible for the way the 911 looks and the unique way it handles.  The Vette isn't going to look or drive appreciably different if they switched to coil springs.

[280Z Turbo]

Economies of scale I imagine.

What?

The springs are the same front and rear? If economies of scale applied here, shouldn't GM just have used coil springs like every other car they make?

[Nethead]

What?

The springs are the same front and rear? If economies of scale applied here, shouldn't GM just have used coil springs like every other car they make?

280Z Turbo:  It's BlowCougs logic .  Straight people wouldn't understand...

[Nethead]

Huh?

The Mustang uses a multilink coil spring setup. That is not the leaf spring setup that I'm talking about.

I've never seen a panhard rod on a standard leaf sprung axle. Every truck rear suspension I've seen has used two leaf springs to locate the axle.

280Z Turbo:  Some really slick ORVs use panhard bars on their rear leaf springs because they use one-directional hinges to connect the axles to the leaf springs--and get improved droop as a result.  There may be ORVs (mostly Jeeps, I expect) that use this same panhard-bar-plus-leaf-springs setup in their front suspensions, although the Nethead here has never seen an example of it.  Without that panhard bar, the pucker factor might rise exponentially on hinged leafs...

The current-year Ram pickups use coil springs in the rear, which improves the ride but cuts the payload considerably.

[GoCougs]

The RR configuration of the 911 is a bit different from leaf springs on the Vette.  The driveline configuration is a defining trait of the 911.  It's responsible for the way the 911 looks and the unique way it handles.  The Vette isn't going to look or drive appreciably different if they switched to coil springs.

Yes, more endemic to the 911 brand than springs, but the point was that both would not exist if but for being a legacy throwback.

[GoCougs]

What?

The springs are the same front and rear? If economies of scale applied here, shouldn't GM just have used coil springs like every other car they make?

Economies of scale also apply to design and assembly $$$.

If it was such a cool/cheap/awesome/whatever technology, lots of other automakers would be doing it. Like the rear-engined 911, no one else does it, and for good reason.

[FoMoJo]

Huh?

The Mustang uses a multilink coil spring setup. That is not the leaf spring setup that I'm talking about.

I've never seen a panhard rod on a standard leaf sprung axle. Every truck rear suspension I've seen has used two leaf springs to locate the axle.

Yeah, I wasn't really sure why the Mustang suspension and leaf springs were being discussed; just wanted to clarify it for those who thought the new Mustang had leaf springs.

As for a Panhard rod, it's been around for a long time; even though it wasn't used on a number of earlier applications.  Even the Muscle cars, generally, only used a sway bar.