The odometer is connected to the tires through a series of mechanical
connections (gears, shafts), so it must correspond exactly to the rotation
of the tires. When adjusted for the effective circumference of the tires,
it should yield an exact distance travelled. The Speedometer, on the other
hand, is driven through that same sequence of mechanical devices, but the
last stage is a magnet rotating past a disk which is attached to the
spring-loaded needle. That is NOT a solid or certain way of connecting
devices together. If the magnet and disk are slightly too close, the speed
will read high (a weak spring will have that same effect); too far apart
yields a slow speed indication.
HTH,
Ken H.
On Sun, Nov 8, 2020 at 10:54 AM 78gmcroyale via Gmclist <
> I'm very confused by this statement.... "I don't think the mph reading is
> the first thing to correct. The first thing to get right is the
> odometer. That's a direct geared readout ofdistance traveled. It needs to
> be correct before the speedometer reading can be addressed if
needed."The
> speedometer cable feeds the speedometer and it's rate of spinning
> determines miles and mph. It can't differentiate between the two. If mph
> is correct then mileage should be correct and if mileage is correct then
> mph should be correct. I don't understand how you can first fix one and
> then fix the
other.What am I missing?Sent from my U.S.Cellular© Smartphone
> -------- Original message --------From: Emery Stora via Gmclist <
> gmclist> Date: 11/5/20 5:47 PM (GMT-06:00) To:
> gmclist Cc: Emery Stora Subject:
> Re: [GMCnet] Speedometer Gear Reducer Adapter You are correct. Set things
> by the odometer. I used my gps rather than a mile marker. I have found that
> mile marked often are off by .2 miles. After setting it I checked it by
> mile markers 100 miles apart. It was within 0.1 miles. Once you have the
> gps for ten miles record the odometer reading at that point. I had an
> adapter from Jim Kanometer and I just sent it back to him and gave him my
> odometer reading for 10 miles on the gps. He changed gears in it and it was
> right on Emery Stora> On Nov 5, 2020, at 2:52 PM, Todd Snyder via Gmclist <
> gmclist> wrote:> > I don't think the mph reading is the
> first thing to correct. The first thing to get right is the odometer.
> That's a direct geared readout of> distance traveled. It needs to be
> correct before the speedometer reading can be addressed if needed. > > You
> could get on the highway, take note of the odometer as you pass a mile
> marker. Drive 10 miles and note the odometer reading. Subtract one>
> reading from the other, figure out the % difference and get a driven gear
> with that % more or less teeth, depending on which way you need it to go.
> > > Then pull your current driven gear out and count the teeth. > > If the
> odometer is reading low, you need fewer teeth on the driven gear. If the
> odometer reads high, you need more teeth. You may or may not be> able to
> get it corrected with the driven gear though, the drive gear only works for
> a certain range of tooth numbers. Looking online there are> transmission
> parts stores that offer assistance with this. They'll know what range of
> teeth numbers will fit with what you have and sell you the> gear> > There
> are also online calculators that can determine the correct driven gear to
> use but you need to know the number of teeth on the drive gear so they>
> won't be much help unless you use them to figure out what's in there by
> trial and error, which you can do. > > > > -- > Todd Snyder, Buffalo NY >
> 1976 Eleganza II> > _______________________________________________> GMCnet
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