Date:         Tue, 25 Aug 2015 15:15:12 -0400
Reply-To:     David Beierl <dbeierl@ATTGLOBAL.NET>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         David Beierl <dbeierl@ATTGLOBAL.NET>
Subject:      Re: shocks how to know if it really failed?
Comments: To: Eric Caron <ecaron1@COMCAST.NET>
In-Reply-To:  <DD1FBAD4-AB6E-41FB-91E3-D7127431605E@comcast.net>
Content-Type: text/plain; charset="us-ascii"; format=flowed

At 12:07 AM 8/25/2015, Eric Caron wrote:
>so does this sound like my front shocks were bad?  is there a way to
>test the old shock to know?

The easiest test is on the vehicle.  Stand on the bumper.  When you
quickly take your weight off, the vehicle should rebound but stop
before it descends below its rest position.  If it keeps on bouncing
for several cycles they are dead dead dead.  When I drove it the
shocks were certainly not in that state or anywhere close.

In system terms that degree of damping (one rebound but not crossing
the zero line on the way back down) is called critically damped.  Not
rebounding past the zero would be overdamped and crossing zero more
than once would be underdamped.  Someone else will have to tell you
how that relates directly to suspensions.

Main function of a shock absorber is to turn mechanical motion into
heat, thus leaching energy from the oscillating system of
wheel/suspension and spring so that it doesn't oscillate.  Ideally
the wheels will track the road surface with constant pressure and the
vehicle will not move in response to road irregularities.  That's
only likely to be achieved with an active suspension using
electronics and pumps.

Some shocks are filled with pressurized gas that also exerts a spring
action -- you can't really compare the feel of those directly against
ones that don't, since the others don't have any preferred position,
they just don't like to move away from any position.

Yours,
David