Say it ain't so....For the first time in about eighteen months I find myself at
odds
with something stated by Joe.
Joe Curry wrote:
> It's really not rocket science. If you raise the pressure to the extent
> that the tires round the tread, you lose traction because the amount of
> rubber on the ground is decreases.
Yes, the amount of rubber on the road and friction would decrease. The weight
of
the vehicle must now be distributed over a smaller surface area (that portion
of the
tire in contact with the road). Hence, the unit bearing pressure (traction)
increases. Think of it as the refrigerator in your kitchen. Try to push that
puppy
around on its four "legs". Small surface area, high unit bearing pressures and
traction. In order for it to slide, you have to exceed its traction
coefficient.
Now, set the fridge on a piece of plywood (increasing the surface area and
reducing
the unit bearing pressures) and push the plywood around. Much easier to break
the
traction and move the beast around.
Best regards,
Ed Hamilton
>
>
> On the other hand, if you decrease the pressure so much that you cause
> the sidewalls to flex, you increase the lateral movement of the car and
> that is not helpful for handling. You also risk rolling the tread and
> lose traction that way.
>
> So the trick is to find that happy point where the pressure is right in
> between those tow points.
>
> Joe Curry
>
> P.S. You never (as was pointed out) want to exceed the manufacturer's
> recommended inflation pressure. They obviously know more about their
> tires than we do.
>
> DANMAS@aol.com wrote:
> >
> > In a message dated 98-08-15 14:52:02 EDT, gernot.vonhoegen@stir.ac.uk
>writes:
> >
> > > while I agree with the thread on pressures, I disagree with the
> > > improvement in handling due to higher tyre pressure. Typically the
> > > improvement is a lower pressure. Higher pressure will give you a better
> > > fuel economy when you drive on motorways where you don't expect much
> > > cornering etc. If you want better handling, you will find that dropping
> > > the pressure by about 5 psi below the recommendet setting will improve
> > > matters. However, that depends on the individual tyre make due to
> > > different grip and wear qualities.
> >
> > Gernot,
> >
> > I'm no expert (not even close), but according to Fred Puhn, author of the
>book
> > "How to Make Your Car Handle," higher pressure will improve handling. I
>quote
> > from the caption to figure 4, page 19:
> >
> > "Notice that you lose more by a small amount of underinflation than a small
> > amount of overinflation. When in doubt, increase the pressure before you try
> > decreasing it."
> >
> > Figure 4 is a diagram plotting grip vs pressure. Grip drops off much more
> > sharply on the low pressure side of the curve than on the high pressure
>side,
> > using optimum pressure as a reference.
> >
> > In the few years I hung out with the SCCA showroom stock racers (as a
> > photographer for a local TV station), I was amazed at the high pressures
>they
> > used - often in excess of 45 psi, all on street tires.
> >
> > Dan Masters,
> > Alcoa, TN
> >
> > '71 TR6---------3000mile/year driver, fully restored
> > '71 TR6---------undergoing full restoration and Ford 5.0 V8 insertion - see:
> > http://www.sky.net/~boballen/mg/Masters/
> > '74 MGBGT---3000mile/year driver, original condition - slated for a V8 soon
> > '68 MGBGT---organ donor for the '74
>
> --
> "If you can't excel with talent, triumph with effort."
>
> -- Dave Weinbaum in National Enquirer
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