<VV> Tires & Speedometers

[Chris & Bill Strickland]

All the tire size for "correct" speedometer readings chat is a bit 
bogus, imo.  If you want "correct" tires, get some bias-ply 6.00 x 13's 
from Coker or somebody -- anything else is something less than 
"correct". It may meet some rules at some goat show somewhere, but it is 
not "correct".  Many people went with 6.50 x 13's the first time they 
replaced the factory tires anyway -- they were cheaper and in stock.

Nor did Corvairs did come originally with calibrated or "Certified" 
speedometers  -- they were just generic, mass produced speedos that 
sorta gave you a rough idea of the road speed -- some worked rather 
well, and some didn't. Calculated figures here are not real life, unless 
you had one of those speedos that didn't come with the car.  And because 
they were such good winter cars, you put on a new set of sawdust 
retreads (when new, they were almost always a much taller tire) at the 
start of each winter season, and took them off when they went bald, 
generally about August 1st, just in time for that summer trip to 
California on the highway tires. Using someone else's tire data for your 
speedo head, well, not everyone likes chocolate ice cream ...

*IF* it is important to you, you could probably do better by figuring 
out what tire circumference gives your particular speedometer head the 
greatest accuracy, and/or by sending your speedo head out to a shop and 
get it "Certified" (used to need the whole car to do this - $$$) or at 
least calibrated, and/or by having a speedo shop build you up a  "ratio 
adapter" to give you a correct speed  for your speedo and the tires and 
gearing that you choose, rather than making tire size choices based on 
someone else's idea of how your speedo should read and what your car 
should look like.  Then when you put on your "winter tires" (for those 
that drive year round), you just change the ratio adapter, too.

There are many shops that provide these services -- just one example is 
http://www.speedometerservice.com/services.php

OR, you could just figure out that your speedo with those tires reads 
about 8.6% fast, and then do the math, which was the "authentic" Sixties 
way, for you Pure Stock types.

A college roomie bought a brand new Camaro in '67 and it would just get 
us back to our hometown in no time flat, about an hour less than what we 
had been driving it, until, smart college students that we were, we did 
the math, and figured out the speedo was about 20 mph slow (and we were 
driving it a little fast anyway) -- last I knew, he still had the car 
with that same uncorrected speedo -- he just drives it accordingly, and 
it is still oem as-delivered "stock", except maybe for the tires. 

also see 
http://www.rodandcustommagazine.com/techarticles/0801rc_mechanica_speedometer_calibration/index.html

Bill Strickland