<VV> Axle Jacking & Limiting droop

[Ken Pepke]

No flame coming your way from me.  You are correct, the outer wheel does push up into the wheel well ... and the high mechanical roll center of the rear axle does roll the tire onto its sidewall.  Remember that the rolling over down force is what is causing the spring to be compressed.  So, the coming back down does not occur until the traction is at its limit or beyond and the down force is decreasing.  It is the loosing of some degree of traction that reduces the downloading thus allows the spring to regain some of its length.  Rolling the tire off the bead or the wheel digging into the road surface may well be sufficient to upset / trip the vehicle into a roll over ... but more than likely it will trigger a spin out.  Either way, control is lost.

Now I ask you to consider the direction in which the 'rebound' straps work.  These straps limit the maximum axle droop.  If the vehicle were somehow airborne [not generally considered to be desireable] the rebound straps will be limiting the droop of the wheel to something less than the shock absorber limits droop when fully extended.  Under maximum cornering conditions the 'rebound' strap will most likely be LIFTING the inside wheel off the road surface!  The outside 'rebound' will not come into play until the wheel has come out of the wheelhouse and gone well past the axle neutral position and into maximum droop.  The vehicle will be well into a roll over situation and at this point control is far beyond the initial point of having been lost.

Are we now in agreement?

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

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> From: "Smitty" <vairologist at cox.net>
> Date: September 19, 2011 5:00:11 PM EDT
> To: <virtualvairs at corvair.org>
> Subject: <VV> Axle Jacking
> 
> Smitty Says;  I have to jump in here because I think most of you don't understand axle jacking.  Yes the loaded "outer" wheel does push up into the wheel well initially but as the lateral Gs increase it starts coming back out again .  The axle wheel assy is working as a lever on a line from the U joint to the tire tread.  If the tread has enough bite the loaded wheel will fold up under the car lifting it, (Jacking the car) until the tire is on it's sidewall "and in a soft tire condition" the rim will dig into the pavement.  At that point you can kiss it goodby.  Rebound straps are to prevent that situation by keeping the tread on the pavement even though it may be sliding.  Fire up your flame throwers but I am sure I am on solid ground with this.