speedometer increments

This is a picture of my speedometer.

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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?

Reply to
badgolferman
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62.5 mph according to that scale..
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..

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Reply to
NM5K

62 68
Reply to
Tom

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

Reply to
C. E. White

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.

Reply to
Jeff Strickland

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?

Reply to
badgolferman

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

Reply to
Asbjørn

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

Reply to
C. E. White

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.

Reply to
badgolferman

Saves a few pennies per car on ink? =3D)

Reply to
Michael

I think most of my cars, GM and Chrysler products before this one, have had tcks between the numbers, but I'm not sure anymore. Next time I'm in a junk yard, maybe I'll checik.

I agree it's silly to have 10 dividied into 4 parts. Would it have cost so much more to put an extra mark in each section?

BTW, you can calibrate your speedometer using the mile posts on most major highways. Well, I don't remember if interstates have them -- I think they do --, but state highways often do, sometimes a short green and white sign maybe even every tenth of a mile. Sometimes a short cement post with the numbers formed into the cement. This goes faster with a passenger helping, because when I'm alone, I keep getting distracted by the need to steer the car, etc. First I'd check the odometer. I did this 2 or 3 decades ago and it was accurate to within 20 or 40 feet over 5280 feet. That is, when odometer number changed or was the same height as the other numbers, I saw the mile post maybe 30 feet in front of me. Hard to tell at 60 mph, but clearly, pretty good. Once the odometer is calibrated, you won't need the posts to calibrate t he speedometer. I think that was accurate to less than one mph. After that, I sort of lost interest, and I haven't checked my new car or one or two of the preiious cars..

Reply to
micky

I assume the thinking was it looked a heck of a lot better than have a big open space between tick marks every 5 mph or having it really busy with tick marks every 1 mph. To me it seems very reasonable. You have tick marks every five mph where you really need them. I look at the 2.5 and 7.5 tick marks as half way between important points and things aren't messy with a bunch of tick marks that are meaningless. Think like this - if you are alittle over the 10x tick mark, you are doing 10x+1 mph. If you are a little under the

10x+2.5 tick mark you are doing 10x+3 mph. A little under the 10X+5 tick mark and you are doing 10x+4mph, etc...... You can probably come close to the figuring out actual 1 mph increment without having a dial with so many marks it it unreadable. If the speedometer dial was smaller, then they probably would only have 5 mph increments. I can't imagine one big enough that 1 mph increments would be useful.

What would you like - just 5 mph increments or 1 mph increments? Which looks better:

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To my eye the original looks best and is the most useful.

Ed

Reply to
C. E. White

Neither. I would want 2mph.

This last one has 8 sections! No good either.

Reply to
micky

I take this back. Measuring speed off the odometer would compound any odometer error you have, and because it's hard to see from the passenget seat, and because most are electronic rather than mechanical now, it would require a lot of attention to know just when it changed.

OTOH, with rotaiting wheels in the odometer, one can tell how close it is to the new value.

Better to use mileposts for both tests,. and cruise control, and better to use a friend to watch the time and the distance. Or the driver can call out when the milepost passes by.

Reply to
micky

So you woult want the ticks to be at 62, 64, 66 and 68 mph instead of 62.5,

65, and 67.5 mph. Big deal.
Reply to
Asbjørn

I don't know about you but I don't like to do calculations while glancing at the speedometer. I just want to look at it and see what the speed is.

Having said that, picture 2 looks best to me. If the needle is between the 60-65 then I know I'm somewhere between 60 and 65. Picture 1 is misleading with the extra ticks.

Nothing I can do about it now. This is my fifth Toyota and none others have ever looked like this. Toyota has always been known for sticking to what works well unless there is a significant upside to changing. I see no usefulness in this change.

Reply to
badgolferman

You can always take the cover off the speedometer and paint out the 2.5 and

7.5 marks:)

If having a few extra marks on the speedometer is the biggest problem with your Toyota, you should be one happy camper. In my world it wouldn't even make 20th place in my list of concerns with the RAV4s I find myself driving on a semi-regularl basis (we have three of them in the family), I worry about - poor seating position, wind noise, weird cruise control switch location, ridiculous heater controls, poor cruise control operation, oil consumption, cargo area rear seat latches that don't work, mediocre gas mileage, harsh/noisy engine (4 cyl), rusty steel wheels, excessive brake pad wear, spare tires that set off the low tire pressure light, difficult to replace spare tire cover....all before I even started to care about the graphics on the speedometer. I have to admit, I don't even remember what the RAV4 speedometer looks like except it is round with numbers and I that have to contort my hand through the steering wheel to reset the oil change reminder button.

Ed

Reply to
C. E. White

Since the error is greater than the increments, does it really matter what the display says? You want to know generally what your speed is -- you are going greater than 60 but less than 70, but the speed limit is only 35, so does it really matter that the pencil is sharp or dull? If the speed limit is X, and your indicated speed is X + 2 or X + 3, does it really matter since the built in error is greater than that? You need to be going X +

10-ish to break the speed limit enough that anybody will care. Well, anybody with a notepad and a radar gun will care. Your car is already designed to tell you that you are doing 60 when the fact is you are only doing about 56. The problems come when the car tells you that you are doing 60 when the fact is that you are doing 65.
Reply to
Jeff Strickland

By the way, here's a picture of the whole set of dials.

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Notice how the tachometer has the normal +2 increments whereas the speedometer has +2.75 increments. That's just inconsistent and misleading altogether regardless if one design looks better than the other.

Reply to
badgolferman

The speedo increments are 2.5, not 2.75. There is nothing strange going on here. Well, maybe it's strange to you, but there is a marketing strategy going on that the design engineers selected a face design that makes some sort of sense to somebody that actually gets paid to decide such things.

Among the many considerations are the issues we have already discussed -- the error rate of the speedo does not necessitate the precision of the extra tick marks -- and the space available to present the information that is intended to be presented. If the speedo error is already 4mph, does it really make sense to add a tick mark for 2mph increments when the same information can be shown with 2.5mph increments? Why does the speedo go to

120 when the car can only do 90 going downhill?

Another consideration is that they (design engineers) know that people want to see the needle point to a certain area when the car is doing 70. The speedo has to start somewhere, and be someplace else at 70, this means there is a given amount of space to indicate all of the information inbetween, and the remaining space has to be divided to fill the space with information that will never ever happen. All of this goes into making a decision on how many tick marks to put on the face of the dial.

Reply to
Jeff Strickland

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