Speedometer off by 5 MPH

[SuffolkD at aol.com]

Mike:
make sure both cars have the same tire size and tread depth.
I also have a radar gun if you want the final answer.
-SCott by BOSTON

> > From: "Mike Del Tergo" <mdeltergo at hotmail.com>
> > 
> > Interesting, One 200 avant spot on, the other -5MPH above 55 MPH as noted 
> by
> > GPS.
> > Now, if MPH off, is odometer off by same amount?  No measured miles close 
> by
> > to calculate.
> > Mike
> My previous response to this thread was:
> 
> A more considered method might be to check the odometer over a 5 mile
> roadside measured course.  You may well find that the stock tire size does
> not give the correct odometer reading, hence you can adjust your new tire
> size to correct this error.  Once you get this right, you can then measure
> the speedo time error over the same course at an indicated 60 MPH and
> calculate the % error.
> 
> Most hiways have mileage markers at regular intervals and to mark specific
> road assets, such as bridges.   Go shopping!
> 
>