speedometer increments

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Old 07 May 2012, 06:28 am   #1 (permalink)
badgolferman
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Default speedometer increments

This is a picture of my speedometer.
http://img192.imageshack.us/img192/7775/photonut.jpg

If the needle was pointing at the first tick mark after 60 MPH how fast
would I be going?

How about if it was between the 70 MPH and the tick mark prior to that?
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Old 07 May 2012, 07:37 am   #2 (permalink)
NM5K
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Default Re: speedometer increments

On 5/7/2012 6:28 AM, badgolferman wrote:
> This is a picture of my speedometer.
> http://img192.imageshack.us/img192/7775/photonut.jpg
>
> If the needle was pointing at the first tick mark after 60 MPH how fast
> would I be going?


62.5 mph according to that scale..
>
> How about if it was between the 70 MPH and the tick mark prior to that?


68.75 mph according to that scale..

My 05 Corolla does not have marks between the numbers..
But I use my GPS readout for the exact mph..

http://home.comcast.net/~disk100/dash1.jpg
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Old 07 May 2012, 07:48 am   #3 (permalink)
Tom
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Default Re: speedometer increments

On 5/7/12 7:28 AM, badgolferman wrote:
> This is a picture of my speedometer.
> http://img192.imageshack.us/img192/7775/photonut.jpg
>
> If the needle was pointing at the first tick mark after 60 MPH how fast
> would I be going?
>
> How about if it was between the 70 MPH and the tick mark prior to that?


62 68



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Old 07 May 2012, 09:14 am   #4 (permalink)
C. E. White
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Default Re: speedometer increments


"badgolferman" <REMOVETHISbadgolferman@gmail.com> wrote in message
news:xn0hxsx3k22c3a000@reader.albasani.net...
> This is a picture of my speedometer.
> http://img192.imageshack.us/img192/7775/photonut.jpg
>
> If the needle was pointing at the first tick mark after 60 MPH how fast
> would I be going?
>
> How about if it was between the 70 MPH and the tick mark prior to that?


For the first mark, in theory, 62.5 mph. However, speedometers are not
accurate enough that the 0.5 is significant. I'd treat the first mark like
63 but assume it is not particularly accurate. Most cars have speedometers
that deliberately don't read low (i.e., the speed shown by the speedometer
is -0 / + 5% of the actual speed), so in reality, I'd assume the first mark
past 60 would represent an actual speed somewhere between 59 and 63 mph
(assuming OE tires). The first mark before 70 (the 67.5 mph mark) would be a
speed somewhere between 65 and 68 mph (again assuming OE tires). So if you
are halfway between the "67.5 mark" and the "70 mark" I'd guess your speed
would be somewhere between 65 and 69 mph (again, assuming OE tires).

If you want a better answer, get a good GPS. I've checked all my recent cars
with several different GPSs and all the speedometers read slightly low to
dead on, with some variation depending on the speed (i.e., might be dead on
at 60, but read slightly low at 70, etc.). Once you change tires, the
accuracy will change as well. If you stick with the OE size, the change will
be very small. If you change to a different size the change can be very
significant.

I don't really think you can cut things as fine as your post indicates you
want to. There are many variable affecting the speedometer readout. And
remember the speedometer damps out small fast changes in speed (in other
words, it averages the speed over small time periods). Say you set the
cruise at 60 on flat level ground - the speedometer might seem to stay
steady on 60, but in reality, your speed is probably constantly shifting by
small amounts around 60 (say 59.5 to 60.5). So, I'd never trust a
speedometer reading (or even a GPS) to be more accurate than +/- 1 mph (and
that is likely optimistic).

Ed
Ed


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Old 07 May 2012, 11:08 am   #5 (permalink)
Jeff Strickland
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Default Re: speedometer increments


"badgolferman" <REMOVETHISbadgolferman@gmail.com> wrote in message
news:xn0hxsx3k22c3a000@reader.albasani.net...
> This is a picture of my speedometer.
> http://img192.imageshack.us/img192/7775/photonut.jpg
>
> If the needle was pointing at the first tick mark after 60 MPH how fast
> would I be going?
>
> How about if it was between the 70 MPH and the tick mark prior to that?



By my calculations, each tick mark is 2.5mph. So, there are 8 marks between
60 and 80, 62.5, 65.0, 67.5, 70 (unmarked but larger than the other ticks)
72.5, 75.0, 77.5, and 80 (marked and larger than the other ticks).

I'm confused by your confusion.


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Old 07 May 2012, 11:53 am   #6 (permalink)
badgolferman
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Default Re: speedometer increments

Jeff Strickland wrote:

>
>"badgolferman" <REMOVETHISbadgolferman@gmail.com> wrote in message
>news:xn0hxsx3k22c3a000@reader.albasani.net...
>>This is a picture of my speedometer.
>>http://img192.imageshack.us/img192/7775/photonut.jpg
>>
>>If the needle was pointing at the first tick mark after 60 MPH how
>>fast would I be going?
>>
>>How about if it was between the 70 MPH and the tick mark prior to
>>that?

>
>
>By my calculations, each tick mark is 2.5mph. So, there are 8 marks
>between 60 and 80, 62.5, 65.0, 67.5, 70 (unmarked but larger than the
>other ticks) 72.5, 75.0, 77.5, and 80 (marked and larger than the
>other ticks).
>
>I'm confused by your confusion.


I have never seen a speedometer with three tick marks between major
divisions. There are always either 4 (2 mph increments) or 1 (5 mph
increments). I think this is silly to have it like that. Who wants to
know if they are going 62.5 mph or 67.5 mph?
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Old 07 May 2012, 11:58 am   #7 (permalink)
Asbjørn
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Default Re: speedometer increments


"badgolferman" <REMOVETHISbadgolferman@gmail.com> wrote in message
news:xn0hxsx3k22c3a000@reader.albasani.net...
> This is a picture of my speedometer.
> http://img192.imageshack.us/img192/7775/photonut.jpg
>
> If the needle was pointing at the first tick mark after 60 MPH how fast
> would I be going?
>
> How about if it was between the 70 MPH and the tick mark prior to that?


In theory, going straight with the right tire dimension, inflation pressure
and load, that should be 62.5 and 68.75 mph,
but in practice probably about 8 - 10 % less like in mine, that is about 57
and 63 mph.
The best way to find out is by using a GPS, may be your phone has one?
The speedometer is not a precision instrument. The bias is dependent of make
of car and make and dimensions of tires.

Asbjørn


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Old 07 May 2012, 12:17 pm   #8 (permalink)
C. E. White
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Default Re: speedometer increments


"badgolferman" <REMOVETHISbadgolferman@gmail.com> wrote in message
news:xn0hxt5m249wi4000@reader.albasani.net...
> Jeff Strickland wrote:
>
>>
>>"badgolferman" <REMOVETHISbadgolferman@gmail.com> wrote in message
>>news:xn0hxsx3k22c3a000@reader.albasani.net...
>>>This is a picture of my speedometer.
>>>http://img192.imageshack.us/img192/7775/photonut.jpg
>>>
>>>If the needle was pointing at the first tick mark after 60 MPH how
>>>fast would I be going?
>>>
>>>How about if it was between the 70 MPH and the tick mark prior to
>>>that?

>>
>>
>>By my calculations, each tick mark is 2.5mph. So, there are 8 marks
>>between 60 and 80, 62.5, 65.0, 67.5, 70 (unmarked but larger than the
>>other ticks) 72.5, 75.0, 77.5, and 80 (marked and larger than the
>>other ticks).
>>
>>I'm confused by your confusion.

>
> I have never seen a speedometer with three tick marks between major
> divisions. There are always either 4 (2 mph increments) or 1 (5 mph
> increments). I think this is silly to have it like that. Who wants to
> know if they are going 62.5 mph or 67.5 mph?


It will be easier to swallow if you don't think of the speedometer as a
precision speed measuring device. I suspect the location of the tick marks
was decreed by the industrial designer and not an engineer. Since most speed
limits are in 5 mph increments, learn to ignore the intermediate marks (the
10x + "2.5" and "7.5" marks) and focus on the ones that matter 20, 25, 30,
35, 40, 45, 50, 55, etc.....

Most car speedomters are not precise or accurate, so treat the reading as a
good estimate and go from there.

Ed


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Old 07 May 2012, 12:44 pm   #9 (permalink)
badgolferman
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Default Re: speedometer increments

C. E. White wrote:

>
>"badgolferman" <REMOVETHISbadgolferman@gmail.com> wrote in message
>news:xn0hxt5m249wi4000@reader.albasani.net...
>>Jeff Strickland wrote:
>>
>>>
>>>"badgolferman" <REMOVETHISbadgolferman@gmail.com> wrote in message
>>>news:xn0hxsx3k22c3a000@reader.albasani.net...
>>>>This is a picture of my speedometer.
>>>>http://img192.imageshack.us/img192/7775/photonut.jpg
>>>>
>>>>If the needle was pointing at the first tick mark after 60 MPH
>>>>how fast would I be going?
>>>>
>>>>How about if it was between the 70 MPH and the tick mark prior
>>>>to that?
>>>
>>>
>>>By my calculations, each tick mark is 2.5mph. So, there are 8
>>>marks between 60 and 80, 62.5, 65.0, 67.5, 70 (unmarked but
>>>larger than the other ticks) 72.5, 75.0, 77.5, and 80 (marked and
>>>larger than the other ticks).
>>>
>>>I'm confused by your confusion.

>>
>>I have never seen a speedometer with three tick marks between major
>>divisions. There are always either 4 (2 mph increments) or 1 (5 mph
>>increments). I think this is silly to have it like that. Who
>>wants to know if they are going 62.5 mph or 67.5 mph?

>
>It will be easier to swallow if you don't think of the speedometer as
>a precision speed measuring device. I suspect the location of the
>tick marks was decreed by the industrial designer and not an
>engineer. Since most speed limits are in 5 mph increments, learn to
>ignore the intermediate marks (the 10x + "2.5" and "7.5" marks) and
>focus on the ones that matter 20, 25, 30, 35, 40, 45, 50, 55, etc.....
>
>Most car speedomters are not precise or accurate, so treat the
>reading as a good estimate and go from there.
>
>Ed


There's no doubt speedometers are not exact, but that doesn't take away
from the sheer idiocy of that particular design. It still baffles me
what they were thinking when someone signed off on that.
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Old 07 May 2012, 01:11 pm   #10 (permalink)
Michael
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Default Re: speedometer increments

On May 7, 10:44*am, "badgolferman" <REMOVETHISbadgolfer...@gmail.com>
wrote:
> C. E. White wrote:
>
> >"badgolferman" <REMOVETHISbadgolfer...@gmail.com> wrote in message
> >news:xn0hxt5m249wi4000@reader.albasani.net...
> >>Jeff Strickland wrote:

>
> >>>"badgolferman" <REMOVETHISbadgolfer...@gmail.com> wrote in message
> >>>news:xn0hxsx3k22c3a000@reader.albasani.net...
> >>>>This is a picture of my speedometer.
> >>>>http://img192.imageshack.us/img192/7775/photonut.jpg

>
> >>>>If the needle was pointing at the first tick mark after 60 MPH
> >>>>how fast would I be going?

>
> >>>>How about if it was between the 70 MPH and the tick mark prior
> >>>>to that?

>
> >>>By my calculations, each tick mark is 2.5mph. So, there are 8
> >>>marks between 60 and 80, 62.5, 65.0, 67.5, 70 (unmarked but
> >>>larger than the other ticks) 72.5, 75.0, 77.5, and 80 (marked and
> >>>larger than the other ticks).

>
> >>>I'm confused by your confusion.

>
> >>I have never seen a speedometer with three tick marks between major
> >>divisions. *There are always either 4 (2 mph increments) or 1 (5 mph
> >>increments). *I think this is silly to have it like that. *Who
> >>wants to know if they are going 62.5 mph or 67.5 mph?

>
> >It will be easier to swallow if you don't think of the speedometer as
> >a precision speed measuring device. I suspect the location of the
> >tick marks was decreed by the industrial designer and not an
> >engineer. Since most speed limits are in 5 mph increments, learn to
> >ignore the intermediate marks (the 10x + "2.5" and "7.5" marks) and
> >focus on the ones that matter 20, 25, 30, 35, 40, 45, 50, 55, etc.....

>
> >Most car speedomters are not precise or accurate, so treat the
> >reading as a good estimate and go from there.

>
> >Ed

>
> There's no doubt speedometers are not exact, but that doesn't take away
> from the sheer idiocy of that particular design. *It still baffles me
> what they were thinking when someone signed off on that.



Saves a few pennies per car on ink? =)
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