[rescue] SLACKERS

[Dave McGuire]

On January 22, Dan Sikorski wrote:
> Do larger tires affect the accuracy of the speedometer?  If not, how
> does the speedometer on most cars determine speed?  It would make most
> sense to me to have it judge the RPM of the axle, and determine speed
> from that, but, if the circumference of the wheel changed, the
> speedometer would be inaccurate.  So, do you have to adjust the
> speedometer if you put on larger tires, does the speedometer gague speed
> a different way, or is the change in circumference of the tire not
> usually big enough to make a difference?

  Most speedometers are driven by a take-off in the vehicle's
transmission.  Changing the size of the tires does indeed affect their
accuracy, by enough of a percentage to make one want to get it
recalibrated.

       -Dave

-- 
Dave McGuire
St. Petersburg, FL         "Less talk.  More synthohol." --Lt. Worf