Bill Kasper wrote:

> i assume the speedo was calibrated for the 185/80-14 size?  if so, then it
> means when i see 65 mph on my speedo i am actually doing 8% faster, or 70.2
> mph?
>
> that's good to know, especially when i am in speedtrapland.
>
> thanks.
>
> bill
> '87 syncro westfalia
> http://www.scruznet.com/~kasper/pics/westy/

You can check with a time-speed-distance calculation.
  Next time you're on an expressway or toll road with marker signs 1
mile apart,
hold the speed steady and measure how many seconds to go a mile.

At 60 mph it should take 60 seconds
At 72 mph it should take 50 seconds.
etc.

Divide the seconds into 3600 to get the mph or vise-versa.
Basic physics.

Larry A.
Chicago