Speedometer calibration available yet?

I thought manufacture do this on purpose maybe to keep the real speed down? Get larger tires to compensate for the discrepancy. It is also a known fact that the mpg display on Prius (without any EV mode in case of PP) is off by ~7%.

Edit: Oh, wait... you are saying your speedometer is already reading slower than actual speed. That is unusual, isn't it? I thought they always read faster than the actual speed. Hmm, then you have to put smaller tires to compensate for the discrepancy. That may also increase the actual mpg to compensate for the mpg discrepancy. lol

 

yep, no updates coming, ever

been going on forever

not gonna happen

 

in fact it's happening right now

 

as we type

 

Don't you mean the speedometer is reading high, not low?

Sorry, but this is standard industry practice here and nearly worldwide, driven in part by laws in some areas that forbid under reading, in a world where the old mechanical speedometers had a significant error spread. Back then, the meters had to be biased high in order to meet the laws. Now it is a very long-standing standard practice.

And this is explained in many other forum threads.

So, no, Toyota is not going to fix it. You can address it by changing tire diameter, or by installing an OBDII-port engine monitor (ScanGauge-II, or smartphone Torque app, or many other products) that will read and display the internal speed being used by the computers, which has far less error.

 

it wasn't so long ago

 

The OP is confusing.

 

First sentence by OP currently says his speedo is reading high. Which is as it should be, and really: if this sorta thing keeps you awake at night, you've got bigger issues.

Switching to bigger tires to "remedy" is a fool's mission.

 

You're not supposed to type and drive, while high . . .

 

while we're singing

 

expectorating covid

 

that is so not in the song

 

I use my GPS for correct speed!

Posted via the PriusChat mobile app.

 

I doubt Toyota will ever fix this problem. With the speedometer programmed the way it is currently, Toyota avoids any possible litigation involving the speedometer from ever reading higher than your actual speed. SO... The best solution I see is changing your tire sizing. I have tire size 195/55R16. I notice the difference in actual vs. speedometer reading the most at 70 mpg, with my gps reading 72 mph. That is roughly a 3.1% difference between the two. Don't quote me on this, but I read somewhere that North American speedometers have to be within 3-4% of actual. Now if you use this handy website I found for calculations: tacomaworld com / tirecalc. sorry about the spacing, but I couldn't post the link.


This will give you a good idea how different tire sizes will help negate the difference between actual vs. speedometer readings. The calculator gives you several different value comparisons between two different tire sizes, most importantly the speedometer difference.
For example with my tire size: 195/55R16 3.1% difference roughly

Tire size 195/60R16 would reduce the difference by ~ 3.14%
Tire size 195/65R15 would reduce the difference by ~ 2.2%

Looks like the 195/60R16 would roughly negate the difference from the actual vs speedometer reading.
Keep in mind these are ROUGH estimates and I don't know how sensitive the speedometer is when changing between each mph or any gps for that matter. I am also not sure if this ratio holds true for all speeds. I think it would be wise to come as close as possible to reducing the differences, but avoid going over the difference.

 

How is it a problem, if speedo reads slightly high?

Changing tire OD’s introduces much more significant “problems”: throws odo off, and a larger OD will (obviously) raise the car, reducing mpg, reduce cornering stability. If you’re ever selling the car most buyers will not be impressed. A lot of tire places (Costco for one) will refuse to install non-stock tire sizes.

FWIW, this “problem” is mandated by various levels of government, in an attempt to slow people down a bit.

 

The factory display reads high by at least 3.17% based on the ecu values with factory tires. The worse thing is you end up driving slower than the speedometer indicates, which often upsets Ram trucks behind you.

I use a $30 obd2 display primarily for coolant temp but secondarily to read actual speed.

A feature I like is the coolant temp alarm which can be set lower than factory. I also have a “not to exceed” highway speed alarm to avoid tickets with no remediation options.

 

Speedometer only or also odometer? Having a 3.3% error in odometer means the battery warranty terminates over 5000 km too soon.

 

Just the dash speedo

 

Yeah the only outlier is the speedo, by design. Too, if speed limit is for example 50 mph, and you absolutely must not fall below that, go 52~53 mph? A lot less involved.