speedometer accuracy

FWIW it may be cheaper to buy new tires that will "fool" your speedometer than pay for lots of excess mileage charges on your lease. Just get out the calculator and start crunching numbers. Good Luck

 

The vehicle is wrong but the dealer won't do anything because it's not defective. Many vehicles are set up with up to 10% error like yours as ticket avoidance, especially vehicles that commonly get modded with bigger tires.

Put oversize tires on to remove error if it's important to you. Not that I cared about speedo accuracy but with 265/75's my speedo is pretty much dead accurate. Curious, though, is the odometer under-reports distance by about 3% now. The odometer would have been very close to dead on accurate before so check your odometer against GPS before assuming it's off.

Are you certain the odometer was inaccurate before the tire swap? I think it's by design: when stock, the speedo is set to be 'fast' for ticket avoidance and the odo is accurate so warranty expires at the right mileage driven. It's all about (legal) risk avoidance for Toyota.

 

This is what mine does. My gps always reads 2-3 mph more then my speedo.

 

This.

 

But it does, it's been demonstrated and you said so yourself. Are you contradicting yourself?

In many countries the legislated error in speedometer readings is ultimately governed by the United Nations Economic Commission for Europe Regulation 39.

The UNECE regulation specifies that:

• The indicated speed must never be less than the actual speed, i.e. it should not be possible to inadvertently speed because of an incorrect speedometer reading.
• The indicated speed must not be more than 110 percent of the true speed plus 4 km/h at specified test speeds. For example, at 80 km/h, the indicated speed must be no more than 92 km/h.

VW's, in particular, can have their speedo accuracy changed by adjusting the programming of the on-board controller. It's commonly done by owners using a VAG-Com when they change tire sizes.

I cannot agree: it's not just error; Toyota won't leave it to chance. They are dialing-in speedo error (setting it to read fast) quite intentionally by programming the computer which additionally compensates for any cumulative D-A error. By the same means, it COULD be made to read slower than you actually are traveling; it MAY not if Toyota wanted to comply with the UNECE regulations (which I believe to be embodied in US federal regulation too, but can't find a citation right now...)

 

It is error, but it is managed error. Any manufacturing process of any significant size will result in a distribution of error centered around some point, probably closely approximating a bell curve. The manufacturers must choose where that bell curve will be centered; if it is right on the actual speed, then some speedometers will read fast, and some will read slow. Speedometers reading slow is a bad idea (perhaps illegal or against governmental regulations) so the manufacturers will set the target center of the error range to be some value that is in compliance with the law.

From my limited experience, that value seems to be a reading of about 5% over actual speed, with a very narrow error range.

 

That is exactly what Chris said.

 

He said the speedo's aren't set to be fast: they quite precisely ARE set to be fast. And they CAN read slower than speed actually traveled, but you'd need either big tires, funky gears or fiddle the computer programming like VW owners can with VAGcom. That's where my disagreement is.

 

He said the speedo cannot display a slower speed than you are actually traveling. We are all saying the same exact thing.

 

That's more like it... when you say can't it sounds like you're meaning to say it's impossible, which it is not.

As to whether the factory would assume liability... I suppose a lawyer would have to pitch in, but back in the day if you got a ticket you could bring a speedo error report in to court and get the speeding offense dismissed. Of course, you might also be written an equipment offense on the spot. Happened to my brother. No one contacted GM to complain about it though... maybe they should have?

 

I personally have stock tires from Toyota, 265/65/17's that are supposedly 31' but when I actually measure them they are closer to 29', which would make for roughly a 5-7 difference at the upper end of the mph/kph scale... When my speedo is at 70 I'm probably more in the 64-65 area. I usually drive about 10 over the limit and people fly by me constantly.

 

Mines out too! Just to note, I have a GPS and the Scanguage II hooked up and they both match each other while the speedo is higher. At 120kph on the speedo the gps and Scanguage read 114kph. I guess it's better this way cause if I drive just over the posted speed limit I'll never get a ticket...

 

just did a 700+ mile trip. my 2wd 215/70/15 tires are about 1/2 worn but since day one with local radar and GPS, at 60 im actually doing 56. im putting new tires and upping to 215/75 or 225/70 for a SLIGHT 2-3% increase and bring me accurate. As far as the actual MILES, yes its off too....you are getting cheated. my 710 mile trip turned 732 +/- a mile or so. Even Map quested the route, and was about 715 miles. In NJ we have mile markers, after 10 miles, im off about 1/2 mile and these signs are installed by surveyors. now that my tires are worn down, its even more evident. just going to up in tire size by figuring out the percentage difference and using this: to figure out the different tire size options.

 

I didn't read this whole thread so if this has been said, disregard. First I have 33's GPS and Truck show a discrepancy of about 3 mph. Also I have read that Toyota has calibrated the speedo to show an Average of the most popular tire sizes which are used on toyotas from stock, up to 32's I believe. I have no idea if this information is correct but it certainly sounds right based on the minor discrepancies we see.

Again, not my info, just relaying what I read want to throw that in before the my dad can beat up your dad posters chime in.

 

ok, so say the speedo is showing about 3mph faster than gps (which is also about what I've noticed), but the odo is right on as several of you guys have mentioned. Then if a taller tire makes the speedo correct, what happens to the odo? Won't it read less miles than accurate? -- just sayin