I plugged the Vanagon gear ratios into a ratio computer to see what RPM we
are supposed to be turning on the highway. The gear ratios can be found
here: http://volksweb.relitech.com/helmut/GEARBOX.HTM and the calculator can
be found here: http://www.xse.com/leres/ss/calculator.html. It appears that
the rear end ratio is either 4.83 or 4.86 so I used 4.83 for the
calculations. My old 185R14 tires have a circumference of 25.7 inches
(tirerack.com figure for Yokohama Y356D tires). According to the figures
with the smaller tires the engine was turning 3798 RPM at 70 MPH and 4340
RPM at 80 MPH. The LT27x8.5R14 tires have a circumference of 26.5 inches,
giving me an engine speed of 3669 RPM at 70 MPH (130 RPM less) and 4193 RPM
at 80 MPH (147 RPM less). Theoretical top speed goes up to 103 MPH from 99
MPH.

Aren't you glad I can now go 4 MPH faster with the larger tires? Ha ha...

Chris,

'85 Westy.