Date:         Fri, 26 Nov 1999 06:15:10 GMT
Reply-To:     Mike Finkbiner <mike_l_f@HOTMAIL.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Mike Finkbiner <mike_l_f@HOTMAIL.COM>
Subject:      Re: Agilis 61 - Ply Rating
Content-Type: text/plain; format=flowed

Volks -

I know people get tired of tires, but I have seen several comments on ply
ratings that indicate there is a lot of confusion.  I certainly don't have
all my facts right, but based on having a father who sold tires and selling
them myself for awhile, I know a bit about the history, and hope this might
clear up some confusion.

Ply rating on a tire doesn't mean what it used to.  When tires first came
out, the cord adding strength to the rubber was cotton or other natural
fibers.  That's one reasong many old cars you see had two spare tires.

At that time, AFAIK, a four ply tire had four layers of fibre all the way
around.  There were no belts under the tread, and the plys of fiber were at
an angle to one another, (bias-ply).  As artificial fibers, like rayon,
replaced natural ones tires became more durable.

When Michelin came out with radial tires, the fibers making up the plys on
the body of their tires did not cross each other. All of the fibers were on
a line from the center of the wheel, like you would measure the radius of
the circle, hence Radial Tires.

Fold your hands in your lap.  If your fingers are parallel to each other,
the are aligned like the fibers in radial tires.

Belts around the outside of the tire, under the tread, are made of kevlar or
steel.  They increase the stability of the contact patch, and the lighter
radial plys allow the sidewall to move more easily without lifting the edge
of the tread off the road.  That's one of the reasons why radial tires give
better traction.

So - belted tires generally have one or two plys on the sidewall.  The belt
often has two plys, so under the tread there are three or four plys.  BUT -
the tire will be called a "six-ply" or "eight-ply" if it has a higher
carrying capacity than a standard "four-ply" passenger tire.

What's important isn't the number of physical plys of fiber, it's the
carrying capacity of the tire.  Look at the load rating, and whether it's
designed for light truck use or not.  Todays artificial fibers are a lot
stronger than the original cotton.

I suspect that "Reinforced Sidewall" tires don't have more physical plys,
just different construction, but I don't know.

- Mike Finkbiner
'87 Westy
Moscow, Idaho

>Subject: Agilis 61
>
>Some of the listees asked me to provide a report on the Agilis 61 tire by
>Michelin.
>
>I recently purchased a set and put them on my 86 GL.  They are C rated with
>6ply sidewalls,
----------------------
6-ply sidewalls????
Really??, or do you mean 6-ply in total (tread plus sidewall)

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