[culver]

My turn to reply:

Thanks, is that the case on road circuits too ?

As for the professional opinions about the Vette’s suspension they are not taken in context of racing, just looking at the suspension of a road going sports car.

because if you want a stiffer anti-roll bar then by definition you end up with a stiffer spring !!
Equally for softer.
usually if you ask a moving component to do more than one job it is a compromise.
it was only to cover that it HAS to do two that I raised it to see how do the race teams and seriosu road users resolve the need to have say soft spring to handle undulations but stiff anti-roll to hadle camber ?
Surely it HAS to be a compromise ? UNLESS there is some magic in the composite that I dont' grasp which makes a difference - hence why I wondered if fitting a mini-damper on the centre sectino of the spring was used.

At some point in the C4 design program the engineers were hoping to use just the leaf spring and skip the anti-roll bar. As you have pointed out this makes it difficult to adjust roll rate independently from spring rate. My understanding is with out changing the spring, you can adjust roll rate by changing the location of the spring mounts. Of course this isn’t very practical and in the end they added an anti-roll bar to supplement the leaf spring. Basically the leaf spring provides 100% of the bump spring rate but only some portion of the roll spring rate (say 50%, I don’t know the actual numbers). I then use the roll bar to provide the rest of the anti-roll. Essentially the leaf provides a base roll rate. The anti-roll provides the additional rate and is used to tune the roll rate. But, for a given roll rate I can use a smaller, lighter anti-roll bar because the leaf spring is helping out. I’m sure this makes tuning the suspension different than with normal hardware but I’m equally certain that people have defined the differences. I many not have the knowledge but I’m sure companies like Lingenfelter Performance Engineering do know how to tune things.


That looks to be for open wheel race cars where it is ULTRA stiff and…
The link is definitely for racecars. The data would hold true for something like a Formula Ford that has very little effective down force. However, you are correct that’s a long way from road car suspension travel rates. On the other hand it’s not way out of line when people are taking a high performance street car to a road course (presumable with a reasonably smooth surface). I have never driven on a tarmac (minus in an airplane) so I’m not familiar with the types of bumps/pavement transitions you would encounter.

"metalistic" bushes, yep they're standard to reduce the vibration…
As I said, I’m just not familiar with the bushing used on the Corvettes. The images were of the new Z06 (505hp, looks to be quite a monster). I would expect that with this version of the Vette ride was back seat to control.
From what I’ve read about Vette’s since the C4 was released the leaf springs have never been a source of any handling issues. The C4 suffered because the suspension wasn’t well mounted. Like a Jag E-Type, the Vette used the drive shafts as one of the suspension links. In addition to limiting the geometry options the car now had some of it’s suspension arms mounted to the chassis and others effectively mounted to the dif housing. When they introduced the C5 they dumped all that and put a lot of effort into making sure the suspension arms were mounted to stiff chassis points. Since the C5 came out I can’t think of anything I’ve read that’s critical of the suspension. The biggest issues have always been visibility (you have that long hood); numb, though precise, electric power steering on the C6 (I can attest to that); shift feel. It would be interesting to talk to some of GM’s suspension gurus about the Vette suspension. I always love it when someone illustrates why conventional wisdom doesn’t always hold true*

*Speaking of defying conventional wisdom, years back Racecar Engineering Magazine had a great article looking at the Panoz front engines LMP cars.
http://www.bevenyoung.com.au/prdt880.htm
The Panoz car was a very unique LMP design. Rather than go with a traditional rear/mid engine LMP design, the car used a front mounted pushrod motor. Basically the guy who was paying the bills said make it this way. Until the dominating Audi’s came out, the Panoz cars were very competitive.
The article said while on the surface this car seams like a bad idea, the designers studied the rules and realized it could be competitive.

Motor: Normally the pushrod motor would be outclassed but in this case the cars use a supersonic air intake. Basically high reving peak hp, isn’t as desirable as a very broad power band. The large displacement pushrod seemed well suited to the restriction rules and the car was never lacking for power (I wish I remembered the details).

Weight distribution and Tires: The Panoz car was more nose heavy than the standard LMP cars (say 45% nose vs say 35% again I don’t know the exact numbers). Well the rules of the class limit the size of the rear wheels to something less that optimal for a rear engined car. At the same time the front tires could be larger than needed. By shifting weight forward, the Panoz car could take advantage of the extra front tire allowed by the rules. I can’t remember why they said it was ok to loose the weight from the back ties. Again, I read this article the better part of ten years ago.

Aero: This was where the car really shown. Because the air intake was in the nose of the car there was no need for the large air scoop behind the driver. This made the rear wing more effective because you didn’t have dirty air coming off the air scoop.

In all it was a fascinating look at how, given a unique set of rules and good understanding of the fundamentals, what seems like a bad idea may actually be a very good idea.
I really need to find that article again.