[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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