> Bradley,
>
> Time yourself cruising at a steady speed for 2 to three miles on the
> interstate based on the mile markers..  Based on your average time
calculate
> your actual speed and compare to your indicated speed.
>
> you should take your average time in 1 mile (say 51 seconds), divide 60 by
> that time in seconds (60/51sec = 1.175 rounded) and multiply the result by
> 60 (1.175 x 60 = 70.5).  That result, 70.5, is you speed in MPH.
>
> 60 divided by seconds in a mile multiplied by 60 = average speed in MPH in
> that mile.
>
> At an idicated 60 MPH my Westy covers one mile in a little less that 58
> seconds, thus 60/58x60=62 MPH.  At an indicated 70 MPH I am actually doing
> 72.5 MPH and at indicated 75 MPH I am doing 77.6 MPH.  These figures are
for
> my 27.5x8.5 14 tires inflated at 50 PSI.
>
> Chris,
>
> '85 Westy.
>
> ----- Original Message -----
> From: "Bradley Flubacher" <flub@ADELPHIA.NET>
> To: <vanagon@GERRY.VANAGON.COM>
> Sent: Monday, February 18, 2002 9:22 PM
> Subject: right sized tires, wrong speed indication
>
>
> > My '84 westy cruises nicely at 75-80 MPH, according to the speedometer.
> > It's got to be wrong. I suspect by about 10-15 MPH.  Any suggestions? My
> > tires are the correct size..
> >
> >
> > Bradley Flubacher
> > State College, PA
> > '81 diesel rabbit
> > '82 diesel westy
> > '82 diesel van
> > '84 GL wasserboxer
> >
>