[Vwdiesel] Speedometer question

[dieseltdi at verizon.net]

I am mulling over various tire sizes  for my Westy AAZ TD conversion   
to bring down the rpms in relation to the trans (1.14 3rd and .7 4th)  
and I got to thinking about the speedometer.  As I recall, the number  
on the face of the speedometer is the number of revolutions per  
mile.  Am I right on this?  The speedo in my Westy is marked with an  
820, since it gets its revs directly from the hub, on revolution of  
the tire, should equal one revolution of the cable and one revolution  
of the speedo gear, right?  Why all of this?  Well a 185/75/14 tire  
has 834 revolutions per mile but a 195/75/14 has 815 revolutions per  
mile and a 205/70/14 gets 822 revolutions per mile.  Any thoughts on  
any of this and which tire size may be best?  Of course all three  
sizes are LT or C rated tires.  Hayden

" Those who are willing to sacrifice Liberty for Security, deserve  
neither Liberty nor Security."  Ben Franklin
"Dictatorships all have common factors:  a government controlled by  
one party, a leader who claims to have special powers outside the law  
to keep the country "safe", secret prisons where people are locked up  
without charges or trial and government opponents are branded as  
unpatriotic and charged with aiding the enemy."

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