[rescue] SLACKERS

[Julius Sridhar]

On Tue, 22 Jan 2002, Dave McGuire 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.

What I usually do is that I get a tire which won't have a different outer
diameter from the original, but I get shorter sidewalls and bigger wheels.

Peace...  Sridhar