You guys are doing this the hard way! Just put a GPS in the car and drive,
it will tell you how fast, how far, average speed, and where you have been.
Now that the "SA" is turned off accuracy will be +/- a couple of percent no
matter what size tires you have. Mine has a detailed map on it so I won't
get lost, plus it sends my position back home and to the Internet. A few AA
batteries will run it for a long time and Lord Lucas won't even know it's
there.
Mark
70 Midget
Nashville
> Here's How I calculated my speed.
>
> 1) check the tire circumference using my wife's sewing tape measure,
calculate
> how many rotations would be required per mile.
> >fourth. Divide by the number of inches in a mile(63360) and you should
get
> >miles per hour.
> >
> >{(rpm/rear end ratio)x 60 x C }/ 63360
> >
> >So for a 4.2 rear end, 69.625 inches per turn of tire, fourth gear:
> >(6000/4.2) x 60 x 69.625 / 63360 = 94.18 mph, at 5k rpm = 78.49mph
> >
> >
> >I'm sure someone with a better memory of math will correct me, but
luckily I
> >play with DNA for a living and don't do gobs of math.
> >
> >
> >
> >> I havn't seen anybody talk about tire size which can have a very
> difinite
> >>effect on speedo error and correct top speed. Look at any tire chart
and
> >>you will see a big difference in tire circumference with the tires sizes
> >>very close together if not the same size. Don't forget to take this
into
> >>consideration. Does anyone one out there have the formula for
determining
> >>top speed using tire circumference, axel ratios, and rpm's?
> >>
> >>
> >>BOB
> >>65 Midget vintage racer
> >>________________________________________________________________________
> >>
> >>
> >Regards,
> >Glen Byrns
> >'59 Bugeye
> >
>
>
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