<VV> Bias vs Radials - zzzzz - speedos & tires

Chris & Bill Strickland lechevrier at earthlink.net
Tue Apr 22 17:03:40 EDT 2008


>Bob Helt's answer should have been the end of this ... question.
>

I sorta agree -- the only GM  speedometers of the Corvair era that were 
actually accurate were those that were calibrated at the factory AND 
used a "certified" speedometer head, identified by the word "Certified" 
on the face of the dial -- generally found in law enforcement vehicles.  
Never heard of a Corvair with one.  Speedometers from the 60's were like 
The Pirate's Code -- they served as "guidelines".  We didn't have GPS, 
or radial tires, either

Think about it -- when the engineers designed the speedo and tranny (for 
EM's), they took a good guess at what tires were going to go on the car, 
but by the time they got around to actually putting tires on production 
automobiles several years later, it was the tires from whichever 
supplier was cheapest, not necessarily the exact tires the engineers had 
designed for.  Since engineers normally design in a "margin of safety", 
they probably tried to guess so the speedo ran high -- not only 
psychological, but lawyer friendly, even then.

 Just one of the reasons I think this fanaticism with tire diameters is 
historically interesting, but completely ridiculous.

Other speedometers can be "calibrated" to read accurately, but GM never 
provided this service to the public, only available privately at most 
instrument repair facilities.  And, if you wanted an accurate speedo, 
say taxis and tow trucks and other services that charge by the mile, 
this is what you did, and that is why I have several calibration gear 
sets somewhere.

There was nothing wrong with knob and tube that modern wire insulation 
wouldn't have fixed (disregarding installation costs), not counting 
rodents, who chew on Romex, too.

some generic comments at --
http://answers.yahoo.com/question/index?qid=20080313170603AAnOr6x

Now Michelin patented the radial tire in 1946, and they were in common 
use outside the US during the sixties, but do to Detroit's resistance to 
redesigning their suspensions for radials, they didn't become commonly 
available in the US until the economic pressures of the 1973 "gas 
crisis".  Anyone remember Goodyear's Custom Superwide Polyglass from 
1967,  the first of the belted bias ply tires?  We drove on what we 
could buy, perhaps because we didn't know any better.  It was the late 
sixties when I got sold on radials when I became aware that Hyster met a 
fuel mileage standard for a government contract for lumber carriers by 
switching to radial tires.

WHAT WE SHOULD KNOW ABOUT TIRES:  A HISTORICAL BACKGROUND, by John Thomson
http://www.jags.org/TechInfo/2001/05May01/tires/historyoftires.htm

Bill Strickland




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