<VV> early suspension changes question

[Ken Pepke]

I am sure you would find the GM produced movie 'Car on Trial' most interesting.  Seems like everyone looked at the book 'Unsafe At Any Speed' and saw the 'tuck under' pictures then accepted his explanation as gospel.  The GM film includes segments of an early model suspension working on a skid pad and generating something over .7G, as much as the engine was able to produce.  It established Mr. Nader's 'tuck under' theory as fallacy.  

While you are correct in saying the transverse spring does not locate the wheel you have assumed I said something that I did not.  The mechanical roll center remains as designed but as that spring acts as a quasi roll bar it lowers the apparent roll center.  It reduces the amount of body roll.  The average driver will read the reduced body lean as 'improved' handling.

As Mr. Nader's 'jacking' does not exist in the first place there can be no assumption of performance modification, either positive or negative.

Ken P
Wyandotte, MI
Worry looks around; Sorry looks back, Faith looks up.

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On Sep 19, 2011, at 1:28 PM, Joel McGregor wrote:

> I don't know about the Corvettes but jacking on a swing axle car is talking about the outside wheel dropping and tucking under during hard cornering.  The straps were supposed to prevent that and that is what the rear leaf was supposed to do also.  The rear leaf didn't locate the wheels so it couldn't change the roll center.  When the rear leaf was doing it's job I suppose you could say that it didn't increase lateral acceleration - only preserved it.  I would say it would increase lateral acceleration by allowing more without jacking.
> Joel McGregor
> ________________________________________
> From: virtualvairs-bounces at corvair.org [virtualvairs-bounces at corvair.org] On Behalf Of Ken Pepke [kenpepke at juno.com]
> Sent: Monday, September 19, 2011 8:54 AM
> To: Vair Views
> Subject: <VV>  early suspension changes question
> 
> Straps used to reduce axle drop were used on mid 50s and later solid axle Corvettes more to limit the axle drop while jacking the car than for performance purposes.  Excess drop required lifting the chassis higher to change a tire and that put too much strain on the 'fiberglass' body, inducing cracks.
> 
> Some Corvairs may have got the straps more as a 'monkey see, monkey do' addition.  Remember, under high performance cornering conditions the axle does not drop, it goes up into the body away from the strap [jounce] and the unloaded wheel on the inside of the turn drops down from the body [rebound] which is desirable because if that wheel / tire leaves the road surface, drive power to the outside / loaded wheel is lost.  That strap would hinder performance.  Most of us have seen that happen in the vans when they run out of shock travel ... a known lateral acceleration inhibiter :-)
> 
> Even before the start of production Corvairs were tested to destruction by Chevrolet.  Chevrolet was good at that.  They knew they already had a design capable of generating higher lateral acceleration than their competition.  Why would anyone think they had to make basic changes / corrections to the design during production?  For the 1964 production they did add a 'camber compensator' which was not a 'compensator' but was a cross mounded half elliptical leaf spring which artificially modified the rear axle roll center and the vehicle roll axis.  This change altered the 'feel' of the vehicle but made very little, if any, improvement in lateral acceleration.
> 
> The 65 and later model suspension did improve lateral acceleration ability a small amount by virtue of keeping the tire surface more parallel to the road surface.
> 
> Ken P
> Wyandotte, MI
> Worry looks around; Sorry looks back, Faith looks up.
> 
> **********************