[alfa] Tyres Again

["The Baylys" <dabaylys@xxxxxxxxxxxxxx>]

Measured my 195/65-14s at a circumference of 1915mm or 75.4 inches.

Miata Calculator gives a 155/80-15 at a circumference of 77.8 inches, a
difference of 3.2%.

If my speedo is correct for a 155 tyre, I am really going slower than
indicated, racking up more miles than actual, and changing my oil more than
necessary.  My fuel usage also seems better than it is.

I believe modern vehicles have an acceptable speedo error of <5%.

Beatle
'67 Duetto
Oz
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