🚀 go-pugleaf

joelga@pebble.org (Joel Garry) wrote:
>On Mon, 13 Jul 1998 08:52:13 -0400, Mike Sweeney <msweeney@nospam.lr.net> wrote:
>>Marc wrote:
>>> Mike Sweeney <msweeney@nospam.lr.net> wrote:
>>> >Marc wrote:
>>> >> joelga@pebble.org (Joel Garry) wrote:
>>> >> >On Mon, 06 Jul 1998 00:12:25 GMT, E. Faubion <in@the.sig> wrote:
>>> >> >>"Mark B." <spam_*this*_@see.my.sig> wrote:

>Hey, watch those attribs, people.

>>Yes.  I thought it would have been obvious to anyone who could read English.
>>Guess not.

>>CoF is the ratio of the force necessary to slide an object at uniform speed on
>>a surface to the pressure of the object against that surface.

>>The manner in which it is variable is that the surfaces change.  A material
>>made of sharp-edged stones would have a higher resistance, glare ice would have
>>a very low resistance.

And smooth asphalt is more grippy than rough stones.

>>Here is a list of things that influence DRAG FACTOR:
>>
>>1. Road surface material (see above)
>>2. Length of slide (longer slides decrease the friction because the tire melts
>>and smears more easily.)
>
>Are you sure the longer slide doesn't increase the friction because the tire
>heats up?  

A long slide will melt the rubber.  Long use of proper threshold
braking can increase the temp from cold to proper operating temp.
With the wheel locked, though, there isn't enough area to spread it
out so it will really increase the stopping distance. 

>>3. Material of tires (makes much less difference than road surface)
>
>How about temperature of tire?

On normal street tires, there isn't much difference with temp.  It
only matters with the higher performance tires.

>>4. Chains (help on ice, hurt on dry surfaces)
>>5. Tread (on dirt and mud and other "loose" surfaces)

Tread matters on all surfaces.  Look at the difference in treads out
there.  There is a lot of R&D being put into tread design.

>>6. Temp. of road surface and air (hot weather, longer stops)

Warm stickey tires grip better than when cold.

>>7. Air pressure (only slight variances)

Actually, for threshold braking, low pressure can really hurt
distance.  The tires deform so much that the contact patch changes.

>>8. Weight of vehicle (only before lockup)

If it matters before, why not after?

>>9. Direction of slide (slight variances)

Yup.

Marc
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