There are 2 accuracy issues with speedometers. One is a percentage of
your given speed. This is controlled by the spring rate on the
speedometer. The other is a constant value off. I.E. Always reading 5
or 10 mph high (or low), regardless of actual speed. This latter
scenario is controlled by the position of the needle on your
speedometer.

A GPS will help determine which scenario you fall in. E.G. if the
speedo seems nearly accurate at 25 mph, but consistently off at 60
mph, you probably are dealing with a precentage problem (5% at 25mphn
is around 1mph, and well within your error of checking range, but 5%
at 60 mph is 3 mph and will be discernible.

Many cars intentionally have the speedo read 3-5% high.

On May 19, 2008, at 4:35 PM, Dennis Haynes wrote:

> Most '84s had speedometers that are down right silly. Your tire size
> is
> really the same as the original 185/82-R14 the van came with. The
> odometer
> is probably also off by 4-5%.
>
> The Speedometer can be re-calibrated by removing the and resetting the
> needle. A speedometer shop can also adjust the spring. The odometer is
> direct geard so just live with the error. VW and many Hondas have
> those over
> enthusiastic speedo's. A cheap GPS is also a good option to see how
> fast you
> are really going.
>
> Dennis
>
>> From: Jamie Fitterer <fittdog8848@HOTMAIL.COM>
>> Reply-To: Jamie Fitterer <fittdog8848@HOTMAIL.COM>
>> To: vanagon@GERRY.VANAGON.COM
>> Subject: Tire Size for 84 Westy
>> Date: Mon, 19 May 2008 17:31:12 +0000
>>
>> I am currently driving on LT 195 75 R14 tires.  My speedometer is
>> off by A
>> long shot.  I am cruising along thinking I am doing around 70 and
>> really I
>> am traveling 50 MPH.  ANy suggestions on a good size 14 inch to run
>> or any
>> suggestions on how to adjust speedometer?  I like the LT tires
>> because they
>> last longer with the extra weight on them.
>>