Argonaut

Not as stiff as I thought. As many of you guys know in addition to my 2007GT I have a C5 Vette. The Vette is a track car and as such I change the wheels and brakes on it alot. I do one side at a time, in other words, instead of jacking the front of the car and then the rear...I jack the passenger side and then the drivers. I can litterally put the jack point just behind the front wheel or just in front of the rear wheel and jack the whole side up...both tires off the ground...with little flex of the chassis. Its incredibly stiff. Today I tried to do the same on the S197 and couldn't. I was really surprised. I mean you could if you were to jack in the middle but I put the jack where the lower arm of the front suspension attaches and it was a no go, three wheels stayed on the ground.

This is no slam on the Stang, I love the car but I was quite shocked with the difference between the two cars and thought it something interesting to share.

jahudso2

The FRC is the stiffest c5 though. a c5 vert vs an s197 might be a closer comparo. but thanks for the info!

Philostang

Hmmm, that's interesting.

When I jack up my rear just forward of the wheel well (at the pinch weld) I typically get the front to raise as well if I'm jacking up more than 10". I do have an MM 4-point roll bar, so that may be helping...? Maybe it's just an indication of where our chassis is really strong and where it is weak...

At any rate, despite all the glory being laden on the current C6 car, the C5 chassis is very nicely done, so I wouldn't be surprised if it is a stiffer chassis.

Best,
-j

pascal

I jack up the S197 from the side all the time with a piece of 2x4, not a problem.

But you're comparing a separating frame car with a unibody car...
Anything with a frame will be stiffer.
Also, among all generation Mustangs, the S197 is the stronger body shell to date.

I have been lazy but I plan to make a jack anchor point under the rocker like the FR500C has, shown in that picture.

908ssp

Sorry Argonaut your description doesn't indicate that the chassis is bending. Wheel travel, sway bar strength and balance point all influence your description.

And uni-body cars are much stiffer than frame cars or space frame cars for the weight. Stiffer and lighter. A formula one car is uni-body. Passenger cars for the street aren't built to be just stiff. They are built to crash well and this requires some flexibility in certain areas so stiffness is not the overriding goal. Old frame cars were much worse. Even truck frames are worse. Jack up a corner of a truck made a few years ago and watch the bed to cab gap close up. A space frame like a NASCAR is stiff but it is built for what it does and there are no doors. I could give a 100 more examples....

pascal

I don't think so.
Jack up a convertible from the rocker and see how well the door open and close as opposed to a full framed car (although, frames flex a little still)...
The main reasons car manufacturers went with unibodies is to save weight and to speed up assembly lines. And also save costs (less parts to produce).

908ssp

Convertible is a special case and doesn't really count since it is designed as coupe with the roof cut off.

The fact is car designs are compromises and if chassis stiffness and weight are the two criteria you're going for a uni-body beats everything else hands down.

jahudso2

Yeah, and the stiffer and lighter you make the chassis, the softer you can make the suspension. Then you can have a decently comfortable ride with excellent handling.

Norm Peterson

If nothing else, the Corvette's rear suspension is going to be relatively stiffer in roll than the Mustang's. The IRS's lower RCH means that to balance the distribution of lateral load transfer you have to make up what the lower RCH gives away by making the springs and bars do more. When you jack up one corner of the car, the suspension at the other end is essentially seeing "roll" (plus some linear vertical "heave"). But since there is little or no lateral force involved, the roll center height effect toward reducing roll vanishes.


Norm

CliffyDeuce

I scared myself the first time I was putting the Mustang on jackstands. Instead of jacking under the K-member, I jacked like I had all my old cars - the normal jack points. Once I had the two on one side done, I went and jacked the other side. As I was getting the jackstand, I saw the car moving out of the corner of my eye. Talk about getting my attention! What really happened is that when I jacked the third point (just behind the left front wheel well), the entire car tipped and brought the rear tire off the ground as well. So I count it as the stiffest car I've ever had (although I don't own a vette...at least not yet).

Cliffy