Another calculator that, when your sized tire is entered, indicates that
when your speedosays 67.2, you are traveling 65mph. So, you are going slower
than your speedo indicates.
http://www.net-comber.com/tirecalc.html

bob

On Mon, Oct 12, 2009 at 5:40 PM, Melissa Mourkas <westywoman@mac.com> wrote:

> I have come to the conclusion that I am not driving as fast as my
> speedometer indicates as people are racing around me and my speedo
> says I am doing 70 mph (and I thought this 1.9L was just really
> peppy!).  I have 15/65/205 tires/wheels.  I have been unable to
> conduct a test using mile markers as they are nearly non-existent
> around here and, no, I do not own a GPS.  (I like maps). My shift
> points seem about 5 mph off the marks on the speedometer as well. I
> followed a thread on the Samba regarding this disparity:
>
> http://www.thesamba.com/vw/forum/viewtopic.php?t=345224
>
> They were claiming as much as 10 mph under at 70 mph (actually
> traveling at 60 mph).  Has anyone on this list experienced this and
> have you tried this ratio-adjusted speedo cable shown in that thread?
>
> The vendor for the adjusted cable is:
>
> http://www.tacomaspeedometer.com/index/index.php?
> option=com_content&task=view&id=15&Itemid=28
>
> I apologize if this has been covered ad nauseum in the past.  I will
> try to come up with something more original next time.  In the
> meantime, thanks to all who choose to reply.
>
>
> Melissa Mourkas
> '84 Westy Honey Bee
> Sacramento, CA
>