Speedometer Accuracy?

[YarisPete]

I have an 09' Yaris LB with an automatic transmission. I drive a lot and when going 55 mph (according to the speedometer) I get passed a lot. When I drive my Durango 55 mph, I pass a lot.

So I tracked it with my GPS and when the speedometer says 55 mph, the GPS says about 52/53. I wonder which is correct? My guess is that the GPS is correct or else I've suddenly begun driving like I was 90 years old!

[Zaphod]

Were you the 1st person to own the car? It could be that the previous owner had put on larger diameter tires, changed the speedo gear and then switched back to the smaller tires for the sale without the changing the speedo gear back.

[YarisPete]

I'm the original owner and the car is stock.

[bst82551]

I have a Yaris with stock wheels as well. I believe the problem may lie in the fact that the bare-bones stock Yaris comes with 14" wheels and every other Yaris comes with 15" wheels (or bigger). The speedometer may be calibrated for the 14" wheels.... or it could just be that Toyota set it to show higher than it is actually going to keep you from getting tickets.

I realized this anomaly a month or two after I bought my Yaris and have since corrected my speed by going approximately 5% faster than what the speed limit is (68 in a 65, 37 in a 35, etc.).

[eTiMaGo]

It seems to be a problem with most yaris (and I heard the Fit did that too). One might think it's a safety feature to get people driving slower, who knows...

[YarisPete]

I guess I was a little surprised by it. The difference is even more on my motorcycle and I suppose I'll get out and measure the Durango.

[Yaris Hilton]

It's already been posted on here that there are different speedometer drive gears for the 14" and 15" wheels. Your tires are either smaller in diameter than the ones it was calibrated for, or underinflated.

May be an issue with reading the speedometer, too. Due to the speedometer being in the center, there's parallax viewing it from normal driving position. It's meant to be viewed from straight on, meaning your head in the center between the seats. From my normal position, if I put the left edge of the speedometer on the right edge of the 55 mark, it's centered over it if I do move my head over to the center.

[Zaphod]

That's weird, mine is a 2009 LB MT with stock 15" wheels and it's always matched my GPS.

I that were mine, I'd definitely verify it with another car and if it was still off, I'd be taking it to the dealership. Who knows, the car may even have been built with the wrong speedo gear.

EDIT: what YH said, you should definitely check your tire pressure.

[bkrownd]

Originally Posted by YarisPete

So I tracked it with my GPS and when the speedometer says 55 mph, the GPS says about 52/53. I wonder which is correct?

This is the way speedometers are designed. They typically read 3% or more faster than the true speed.

[GrimlockGT]

The problem is that other drivers assume you and your Yaris are slow, so they want to pass. I get passed more often in the Yaris than our other cars.

[nemelek]

Mine is very accurate. Within .5%. Assuming that the speed odometer and the odometer are in sync, the best way to to test them is using the highway mile markers on a road trip. Press the milage reset button as you pass a marker and drive 10 miles. Then compare the difference. Do this 3 times to get an average. You can also drive exactly 60 mph and time how long it takes to drive 10 miles. Do the math and know exactly how accurate your speed odometer is.

[RETRO]

mine is 1.5 mph faster than the GPS

[Stove]

Originally Posted by bkrownd

This is the way speedometers are designed. They typically read 3% or more faster than the true speed.

And there is an allowable tolerance of error during manufacture. Federal law is +/- 10% for Speedometers I believe. Most car makers keep it a lot closer to nominal. Some will read spot on and other will read a little high. It's really rare to find a stock car that has a speedo that reads slow. The requirements were set up around the old cable driven speedometers and have never been updated to line up with today's more accurate systems.

On a side note, there was some speculation a few years ago that car makers were manufacturing the speedometers and the related hardware so that it always read faster than what the car was going. This runs the warranty out quicker and before the car hits high enough actual miles to end the warranty. For example, if your speedo reads 5% higher than actual speed then your Odometer is also reading the miles 5% faster. On a car with a 36,000 mile warranty, at 5%, the car has only actually traveled 34,200 miles when the Odometer reads 36,000 (OP's post indicates around a 4.5% variance so he has approximately a 34,400 mile warranty). Obviously, the higher the mileage limit on a warranty, and the bigger the variation form true speed, the more beneficial it is to the manufacturer to have the speedo read higher than actual speeds and register miles faster than it should.

[STC]

Mine is a 2010 with 15" steel wheels...
GPS is dead on!

I'll have to try the mile marker to mile marker for ten miles @ 60MPH to see how it matches up! Thanks

[Buddy Fan]

I find my speedometer to be accurate within 1 mph. As a side note, my old Entourage was off by 3 mph at 65 and my wife's Sonata is off by 2 at 65. I had the misfortune of renting a Dodge Caliber and it was spot on accurate for what it's worth!

[bkrownd]

Originally Posted by Stove

For example, if your speedo reads 5% higher than actual speed then your Odometer is also reading the miles 5% faster.

That isn't necessarily true. The speedometer needle could easily have an offset that makes it different from both the odometer and reality. (It's possible the offset is smaller and/or more linear than in the old days, though.)

[Bella]

Originally Posted by YarisPete

I have an 09' Yaris LB with an automatic transmission. I drive a lot and when going 55 mph (according to the speedometer) I get passed a lot. When I drive my Durango 55 mph, I pass a lot.

So I tracked it with my GPS and when the speedometer says 55 mph, the GPS says about 52/53. I wonder which is correct? My guess is that the GPS is correct or else I've suddenly begun driving like I was 90 years old!

Nah it's a pretty common issue - Toyota confirmed to me that the YR is out by about 6% .. But mine is out between 6.5-8% depending on the GPS I use.

Originally Posted by eTiMaGo

It seems to be a problem with most yaris (and I heard the Fit did that too). One might think it's a safety feature to get people driving slower, who knows...

Odd safety feature, considering if you sit on the speed limit per the speedo you're more inclined to be tailgated, which increases instances of road rage! I think there is something in the new design rules for Australia re: speedo errors. Though so many people use GPS these days it's easy to pick up where there is a discrepancy.

[IllusionX]

i had lightly smaller tires... 195/55R15. i'd say my GPS is dead on with the speedo.

now that i have 195/60R15's (tires for cheap), i'm a tiny bit faster than i should be. but who cares really?