2014 C7 Chevrolet Corvette

[vtmike]

Originally Posted by ZDan

Lots of positives, few negatives associated with composite leafs used instead of coils for springs in the Corvette's all double-wishbone suspension.

If they are so great why aren't they used in any other modern performance/supercar?

Sent from my Galaxy Nexus using Tapatalk 2

[ZDan]

Originally Posted by vtmike

If they are so great why aren't they used in any other modern performance/supercar?

That they aren't is not evidence that they are inferior. If you understood how springs work in the context of a proper all double-wishbone suspension setup, you wouldn't be assuming they are a drawback. There are many technical advantages, along with some disadvantages on the practicality/cost side (no real disadvantages from a performance perspective).

http://en.wikipedia.org/wiki/Corvette_leaf_spring

One disadvantage listed:
Perception. Due to its association with spring-located solid axles, the leaf spring has a stigma unrelated to the spring itself.

[SubieNate]

Because every other manufacturer switched to coils forever ago for one reason or another and has just rolled with that.

When properly used, a composite leaf spring can be lighter, it reduces unsprung mass, and positions more of that mass in a more centralized location.

It does impose some unique packaging restraints, which happen to work well with the rear transaxle system in the Vette.

A spring is a spring is a spring. As long as it gives X spring rate over Y amount of travel and stays relatively linear or close to a designed progressive rate, the rest of the suspension doesn't care how that spring rate is generated. The problem with traditional life axle/leaf spring suspensions is the lack of independent rear and the compromised suspension geometry that results from that type of spring mounting. A good transverse setup can be very very nice.

If it were so inferior, no one would be using Corvettes for ALMS or any other racing series.

Nathan

[Mitch]

Originally Posted by vtmike

If they are so great why aren't they used in any other modern performance/supercar?

Sent from my Galaxy Nexus using Tapatalk 2

It's not that they're "so great". They're just not worse. Other manufacturers moved to the McStrut early and have spent their development dollars there. Chevrolet chose to continue refining the leaf design. The result is a six-of-one, half-dozen-of-the-other relationship between the two designs. It would be costly for any other manufacturer to switch to a leaf design (especially without infringing on active patents held by Chevrolet) at this point, and there would be no return for the investment since the performance is comparable. Likewise it would be costly for Chevrolet to switch the Corvette to the coil spring design, and would involve giving up the fruits of their R&D investment in the leaf design. So they're both good, and neither side has an economic incentive at this point to switch to the competing design.

[vtmike]

C6r uses coil springs. Appears to me to be a cost cutting measure in an area that shouldn't be skimped. The fact that no other car manufacturer does it is valid. If there was any worthwhile advantage over coil springs you would see them In other more high end cars.

Sent from my Galaxy Nexus using Tapatalk 2

[ZDan]

Originally Posted by SubieNate

If it were so inferior, no one would be using Corvettes for ALMS or any other racing series.

Er, they actually use coils in the C6R race cars. One reason is that coils are more quickly/easily changed out to get a different rate (and since so many companies make coil springs, it's cheap to get a lot of different rates). I think some series specifically outlaw leaf springs, too.

[ZDan]

Originally Posted by vtmike

C6r uses coil springs. Appears to me to be a cost cutting measure in an area that shouldn't be skimped.

Wrong, the composite leafs are more expensive than coils.

The fact that no other car manufacturer does it is valid. If there was any worthwhile advantage over coil springs you would see them In other more high end cars.

Your logic = flawed.

Learn more about them as they are used in the C5/C6/C7 Corvettes.

[SubieNate]

I stand corrected in the C6R. Makes sense to switch to coils for a race car where you want to change rates frequently.

@vtmike. Give us a valid engineering reason why they are inferior and we can talk about that. Until then, it's no different than someone saying that flat engines are inferior because only Porsche and Subaru use them anymore. "If flat engines are so good, why doesn't Ferrari or Lamborghini or Pagani or insert company name here ___ use them?" Because A., the advantages/disadvantages are totally dependent on the rest of your car's design and their car doesn't call for that design choice, and B., they've invested tons and tons of money developing motors with other arrangements and they have the know how to make those arrangements work well.

Nathan

[fatoni]

Originally Posted by vtmike

C6r uses coil springs. Appears to me to be a cost cutting measure in an area that shouldn't be skimped. The fact that no other car manufacturer does it is valid. If there was any worthwhile advantage over coil springs you would see them In other more high end cars.

Sent from my Galaxy Nexus using Tapatalk 2

boxer motors suck too then i suppose

[vtmike]

Again, their own race car has coils. And you can't tell me that other manufacturers with higher budgets for r&d, higher budgets for total cost of components for more expensive purpose built machines wouldn't have used composite leaf set up if there was a performance advantage to it.

Sent from my Galaxy Nexus using Tapatalk 2

[vtmike]

Originally Posted by SubieNate

I stand corrected in the C6R. Makes sense to switch to coils for a race car where you want to change rates frequently.

@vtmike. Give us a valid engineering reason why they are inferior and we can talk about that. Until then, it's no different than someone saying that flat engines are inferior because only Porsche and Subaru use them anymore. "If flat engines are so good, why doesn't Ferrari or Lamborghini or Pagani or insert company name here ___ use them?" Because A., the advantages/disadvantages are totally dependent on the rest of your car's design and their car doesn't call for that design choice, and B., they've invested tons and tons of money developing motors with other arrangements and they have the know how to make those arrangements work well.

" The last comparison between spring type is how much body coupling do the two spring types have? The body roll coupling of a coil spring on a fully independent rear suspension is nearly zero. That can not be said about a transverse leaf spring since the spring is attached to the frame at the center and both wheels. If the frame rolls, the wheel outside the corner is compressed while the inside wheel is unloaded by whatever the body roll produces. This is in addition to normal weight transfer of cornering. The suspension is not truly independent since the transverse spring makes them dependent on each other, and the motion of the frame / body."



Nathan

" The last comparison between spring type is how much body coupling do the two spring types have? The body roll coupling of a coil spring on a fully independent rear suspension is nearly zero. That can not be said about a transverse leaf spring since the spring is attached to the frame at the center and both wheels. If the frame rolls, the wheel outside the corner is compressed while the inside wheel is unloaded by whatever the body roll produces. This is in addition to normal weight transfer of cornering. The suspension is not truly independent since the transverse spring makes them dependent on each other, and the motion of the frame / body."


Sent from my Galaxy Nexus using Tapatalk 2

[ZDan]

Originally Posted by vtmike

Again, their own race car has coils.

For reasons already presented. It's a lot easier/more practical to have a much bigger variety of different coil springs than leafs. And it's quicker/easier to change out coilovers than leafs.

And you can't tell me that other manufacturers with higher budgets for r&d, higher budgets for total cost of components for more expensive purpose built machines wouldn't have used composite leaf set up if there was a performance advantage to it.

You could say the same about Ducati using desmodromic valve actuation.

There's more than one way to skin a cat.

Meanwhile, if you don't know the actual technical ramifications, you cannot really speak to any advantage or disadvantage, now can you?

[ZDan]

Originally Posted by vtmike

" The last comparison between spring type is how much body coupling do the two spring types have? The body roll coupling of a coil spring on a fully independent rear suspension is nearly zero. That can not be said about a transverse leaf spring since the spring is attached to the frame at the center and both wheels. If the frame rolls, the wheel outside the corner is compressed while the inside wheel is unloaded by whatever the body roll produces. This is in addition to normal weight transfer of cornering. The suspension is not truly independent since the transverse spring makes them dependent on each other, and the motion of the frame / body."
2

In any car that uses sway bars, the left right re not "truly independant".

If they wanted to make the transverse leaf "truly independent", they could by rigidly clamping it in the middle.

BUT,
It is advantageous to mount them at two points such that you get some anti-roll from the leaf, thereby reducing the size/weight of sway bar required.

ADVANTAGE: Leaf springs

[vtmike]

Except you can adjust a sway bar. Not to mention some track set ups run with no sway bar. Also porsches active sway bar disengagement system that takes advantage of the true independent suspension that isn't possible on a transverse leaf spring set up.

A pushrod coil suspension eliminates the packaging advantages of a transverse leaf spring. Ride heigh adjustability. Individual corner spring rate adjustability.

Sent from my Galaxy Nexus using Tapatalk 2