Divide your seconds per mile into 3600 and you will get mph.

Example:  If you go one mile in 50 sec,  3600/50 = 72 mph

Larry A.

On Tue, Oct 13, 2009 at 1:20 PM, Chris S <szpejankowski@gmail.com> wrote:
> I use the mile markers while traveling a sufficiently open stretch of road.
> I like to do several 1-mile sections for an estimated average.
>
> To figure out how many seconds per mile you SHOULD be moving at a given
> speed: �60 * ( 60 /Indicated speed) = seconds per mile.
>
> To figure out how fast you're ACTUALLY moving given a certain number of
> seconds per mile: �60 / (Seconds in a mile / 60).
>
> So, if you're traveling at 51 seconds per mile, 51/60=.85, and 60/.85=70.6
> mph.
>
> Hope that helps to put you in the ballpark.
>
> I've said this dozens of time, but I'll say again that both my '85 Westy and
> '84 Westy have fairly accurate speedometers with stock tires, which I
> understand is a bit unusual.
>
> 2009/10/12 Melissa Mourkas <westywoman@mac.com>
>
>> 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
>>
>
>
>
> --
> Chris S.
> Disclaimer: "Death and serious injury may occur"
>