Good advice always. My tire is the stock size to match the stock speedo,
but the speedo is known to run about 12% low so we know we got errors anyhoo.

My goal is to check the accuracy of the tach. If ground speed is known
with a GPS and the ratios of the engine bone connection to the
transmission bone connection to the differential bone connection to the
tire bone connection to the road bone are known then engine rpms should be
derivable, with windage for torque converter bone slippage tossed in.

Will a defective forward clutch in the AT upset any of the bone-to-bone
ratios?

--
Mike "Rocket J Squirrel" Elliott
71 Type 2: the Wonderbus
84 Westfalia: Mellow Yellow ("The Electrical Banana")
74 Utility Trailer. Ladybug Trailer, Inc., San Juan Capistrano
KG6RCR

On 11/17/2007 12:18 PM John Bange wrote:

> On 11/17/07, Michael Elliott <camping.elliott@gmail.com> wrote:
>> Bitchin'. Thanks, John!
>
>
> one other noteworthy bit: since the speedo is calibrated for 805 revs/mile,
> if you have a left front tire that is anything but 25" in diameter
> (5280/805*12/pi=25.0535582), your speedo indicated speed will be off a bit.
> Personally, I hardly even look at my speedo, insted just using my GPS.
>
> --
> John Bange
> '90 Vanagon - "Geldsauger"