oneor11

Hi all,

I took my phone GPS and checked the speed and it was consistently 2 miles below what my car speedometer showed (i.e. 63 mph when the needle was at 65). The phone GPS seems to match the speed in my 2004 Honda Accord and 2008 Chrysler Town and Country spot on. Have any of you tested the speedometer? I wonder if there is a way to better calibrate it. I have the 18" wheel package, but didn't think that made a difference.

Interestingly, when I had a 2013 Toyota Avalon rental a couple of months ago I played with the digital speed display in the car (the digital speed is a display option in that car). I observed then that the analog speedometer and digital speedometer didn't quite match. I recognized I had to put the needle on the analog a bit over the number to get the desired speed on the digital display. Now I'm thinking that the "a bit over" amount was 2 mph, the discrepency I'm seeing between my ES and the phone GPS.

Any thoughts?

Jacob

Joeb427

iTrader: (1)

The actual speed at 65 on the speedo is about 2-3 MPH less on many vehicles.

oneor11

Ahh okay. Thanks for the education Joe.

Dave Mac

That +2 mph is exactly what I have found on every Lexus I have ever owned so I've always assumed that is what was intended.

Dave Mac

gfr1

Checking via the typical GPS isn't a precise value, but probably the best available, with a couple of considerations. One is, if your GPS readout is in full MPH and not in fractions, the decimal value will be dropped and not rounded. Such as, 59.99 mph will read out as 59. Then, hill variations, though typically small, will always indicate more on the speedometer than on a GPS. GPS measures over the surface of the earth, whereas the odometer shows the surface of the road. If you took an odometer up and down a theoretical equilateral triangle mountain that has 1 mile per side, the odometer would cover two miles, but the GPS would only show the distance covered over the earth, or one mile. Or, if you could take an aircraft straight up over the surface of the earth (no wind), The air speed indicator would show your velocity through the air, but the ground speed (& GPS velocity/distance) would show "0", because no distance would be covered. (Been there & done that,)

My ES300h has standard 17" Michelin tires. And, I have a professional quality Race Logic "Performance Box" GPS that is used as test gear. It updates at rate of 10 times per second and reads out to two decimal places. Tires set at 36 PSI (cold), I drove over 700 miles, at 60 to 80 mph, in the gently rolling roads of west Texas. On a couple of shorter checks, it gave the same relative results. First, my odometer actually read less than the GPS distance value (which reads in feet, by the way, or 5,280 per mi.), which is unusual. In fact, it reads 2.5% low. So, that would affect the speedometer reading, as a relative value. With that known error, my speedometer reads right on from 65 mph to 80 mph. At 40 to 60 mph, it reads about one-quarter mph high and about one mph high at 30, for some reason. Your results, as the saying goes, will vary.

txes

Some variances are acceptable under federal guidelines.

Start changing the diameter of the tire/wheel combinations and
The results can be much more.
http://www.foxnews.com/leisure/2012/...-speedometers/

John

ElliotB

I have a Scan Gauge which is very accurate (radar checked). The difference in true speed to reported speed varies from 1-3 mph depending on the speed. For example, at 28mph the difference is 1 mph (speedometer shows 28, actual speed is 27) while at 65mph the difference is 3 mph (speedometer shows 65 while the actual speed is 62).

A couple of interesting notes about the speedometer. If you are driving at a constant speed with the cruise control on while on a level road and reset the average speed display, the true vehicle speed will be shown. I have the Radar Cruise Control and the digital display speed is off slightly compared to both the speedometer and Scan Gauge. The car's computer knows exactly how fast the car is going. The average speed reported is typically identical to the Scan Gauge speed.

For some reason, Toyota consistently has their speedometers showing slightly higher than true speed.

gfr1

What you say may be true, but the Scan Gauge has no inherent ability to display accurate speed. It uses internal programmed electronic data. It has no way of knowing the size of tires that you might have installed, for instance. It has no sensor input to determine velocity over the road, other than what has been programed. Jack up the rear wheels, rev the tires to 20 mph and the scan gauge will show a speed, but not the actual speed. Therefore, with the scan gauge, you have the same unknowns as those without it, other that when you compare your readings with some other assumed speed value. GPS, Doppler radar and the like, at least have a measured output, as long as they have been properly calibrated.

CurryPot

Lean forward so you are looking 90 degrees at the speedometer. It will then match your GPS.

Mine looks like it is 1 to 2 mph over until I lean forward. Just the angle of the speedometer that is causing the off reading. I know this because when my radar cruise control set at 60 mph, my speedometer looks like 61/62 mph until I lean forward and then it is magically 60 mph.

mrBillFL

there are a few radar signs that show your speed (and blink if you are speeding). the speed shown was always a little lower then my speedo.

SW17LS

Every Toyota/Lexus product I have owned (6) has had a speedometer that reads 2MPH fast.

gemigniani

Since the 1970's Toyota speedometers have been calibrated to read 2 MPH faster than actual vehicle speed. One obvious unintended consequence is that you'll get a few less speeding tickets over the life of the vehicle.

SW17LS

Yep, I have to remember when I'm driving the Jeep that the speedometer is dead on accurate LOL. Cruise set to 80 on the highway in the Lexus is 13 over. In the Jeep its 15 over...15 over is apparently a bigger deal...trust me

ElliotB

"but the Scan Gauge has no inherent ability to display accurate speed"

While this may be true, I have owned this scan gauge for several years, have used it 4 Toyota products (2 Lexus), and have had the opportunity to check it numerous times over the years against local radar, it has consistently been accurate. And it corresponds precisely to the built-in "Average Speed" menu item as per my description above. And as also noted above, Toyota speedometers are 'know' to be inaccurate by about 2 mph.

The bottom line is the car knows how fast it is going and is quite accurate in determining its speed (on a stock vehicle).

gfr1

Fair enough! No argument from me. I actually only commented because, if taken at face value by others, they might feel that the Scan Gauge display accuracy applies to their vehicle. And, it wouldn't, unless compared to a known value. And, that same qualifying comparison would then equally apply to that vehicle's odometer/speedometer display.