[DeTomaso] Firestone recomendation
JDeRyke at aol.com
JDeRyke at aol.com
Thu Apr 1 14:26:27 EDT 2010
This is the most ludicrous collection of 'speed secrets' I've yet seen for
street cars. First, the air inside a tire isn't "dirty". It may have some
water vapor in it, which can lead to deterioration of the rubber and possibly
the metal wheel- over decades of time. Water vapor also expands under heat
and contracts when cool which is important if you're a sensitive enough
driver to feel the traction changes from 2-lb variations in tire pressures. The
odor of old air from inside a tire comes from rubber plasticizers- important
to keep the rubber supple and non-hardening.
To get rid of the water vapor and resulting small pressure variations,
real-racers use nitrogen which is dry. Air from a compressor that is run thru a
commercial refrigeration-drier also works. Helium is a 'leaky' gas and won't
last long. It also costs far more than nitrogen.
No one removes the schrader valves from tire stems "for lightness"; a
schrader valve weighs less than 1 gram (1/454th of a pound!) Instead, one uses
angled valve stems that point the stem at an severe angle to the rim so
centrifugal force cannot pull the valve stem open above 250 mph. This is important
at Bonneville but not at other places. There is no 'torque value' on a
valve-stem cap. Most have no hex for a wrench- a definite clue that
'finger-tight' is fine. All thats necessary is to seat the soft rubber gasket inside a
metal cap- with fingers. A metal hex-cap if overtightened will strip the
soft brass threads of a valve stem. We snug the shiny chromed-brass logo-caps
up to keep children from stealing them for their bicycles.
I also recommend metal valve stems- not as a 'speed secret' but to prevent
ozone & sulfur from attacking the rubber and cracking it. A cracked rubber
valve stem can catastrophically fail from such atmospheric damage- as well as
being easily knocked off by road debris. This has happened to Panteras on
road trips at near-legal speeds. FWIW- J DeRyke
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