Jeff sez:

> I posted this question a week ago and didn't receive any responses so I
> thought I would try again.  Any input is appreciated.

Jeff, here's a previous email I sent to a friend of mine about the subject
of engine RPM at highway speeds.  I hope you find it helpful:

"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. The 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 we were turning 3798 RPM at 70 MPH and 4340 RPM at 80

MPH. The LT27x8.5R14 tires have a circumference of 26.5 inches, giving you

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 you can now go 4 MPH faster with the larger tires? Ha ha..."

Chris S.

www.knology.net/~vw/