Re: tyre pressure

[Andrew Duane USG/PE <duane@zk3.dec.com>]

Hairy green toads from Mars made Osman Parvez say:

> paul:
> > I have heard that for driving on sand, you should reduce tyre pressures
> > to get more of the tyre in contact with the sand.  Does the same thing
> > apply to snow driving?
>
> >NO!
> >when driving in sand, the object is to float on the sand.
> >otherwise, your belly be dragging and your wheels be hanging.
> >hence, low tyre pressures, so they don't cut in and sink.
> >when driving in snow, the object is to get the tires on the pavement.
> >in this case, low pressure = no traction
> >frank
>
>
> Right... that is why, for winter time many people switch their performance
> rubber for snows of a smaller width. 205s to 195s say. Except, It's often
> suggested that running on a lower inflation pressure will aid traction in the
> snow as well. I believe the logic is that decreased inflation pressure
> will increase the length  of the contact patch, while keeping
> the width of the contact patch the same.
>
> I'mnot sure if I agree with you on this point. You definately don't want float
> in the sand... but I don't think decreased tire pressure in the snow will
> inhibit the tire's ability to "cut in and sink". Hmm... food for thought I
> guess. ;) If I had to wadger, which I will this winter... I would probably run
> at normal tire pressure if I had snows, or if I had all seasons, I would run
> a few Psi less than during the summer. Any tire experts?

Done both.

My brother (who lives on Cape Cod) spends a lot of time driving
the beaches in his Cherokee. The rule is generally that you must
drop your tires to 12 pounds to go out on the sand.

This is so you baloon out and float on the sand, since you can't
sink all the way through it to pavement. I've done this (once) in
my 100Q. Boy, it looked and rode wierd with 12 pounds in the tires.
Made it all the way out, though.

In snow, you generally want to cut through the snow to pavement.
However, sometimes the snow is just too deep for this. If this is
the case, and you have good knobby snow tires on, the same principle
can apply: spread out the load and bite a lot of traction surfaces
into the snow.

Note that body roll is greatly exxagerated, which can make turns
more fun than should be allowed by law. Be careful.

--

Andrew L. Duane (JOT-7)			duane@zk3.dec.com
Digital Equipment Corporation		(603)-881-1294
110 Spit Brook Road
M/S ZKO3-3/U14
Nashua, NH    03062-2698

Only my cat shares my opinions, and she's too heavy to care.