Date:         Sat, 14 Mar 2009 17:25:17 -0400
Reply-To:     Mike <mbucchino@CHARTER.NET>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Mike <mbucchino@CHARTER.NET>
Subject:      Re: Tires - Why oh why NOT?
Comments: To: pdooley <psdooley@verizon.net>
Content-Type: text/plain; charset="iso-8859-1"

  "I seem to remember"...."other list members said"......."I made that assumption"......

Never assume anything.

This has nothing to do with the Vanagon's body/ chassis ' torsional rigidity".

Here's some facts;

Weight = mass 

Length = arm

Mass X arm = moment

'Polar' refers to rotation about a given axis.

'Inertia' refers to " an object in motion tends to remain in motion", and also "an object at rest tends to remain at rest".

The way I'm referring to it is;
"polar moment of inertia" is referring to an object rotating about an axis, with a center of mass located a distance away from the axis, and having inertia due to motion, which causes a tendency to want to have more rotational effect, the more the mass and/or the longer the distance from the axis.

Therefore, a rear-weight biased vehicle in motion, will have a stronger tendency towards over-steering (or over-rotation about the vertical axis) and resultant difficulty of control.

This will cause such a vehicle to put heavy stresses upon the tires, possibly popping the tire bead off of the rim on under-rated/ under-inflated tires during such an incident.

Hope this helps you to understand what I meant, and what I was getting at.

Mike B.

  ----- Original Message ----- 
  From: pdooley 
  To: 'Mike' ; vanagon@GERRY.VANAGON.COM 
  Sent: Saturday, March 14, 2009 4:53 PM
  Subject: RE: Tires - Why oh why NOT?


  I seem to remember the old bay window buses handle the snow and ice better
  due to more weight on the rear as compared to the Vanagon.  Add that to
  other list members saying the Vanagon is balanced if not heavier on the
  front axles, and I made that assumption.
  So, has anybody actually weighed a Vanagon with typical fuel and passenger
  load and determined the weight per axle in a real world situation? 

  Regarding the polar moment of inertia, I didn't bother to bring up the axes
  of orientation since the terminology is incorrect in the first place.
  For your argument I think the term "center of mass" fits better, since we
  are still talking about weight distribution and not rigidity.