Is there a size limit to the "Tire change calibration"

because it is cheaper to have 1 tpms antenna and use wheel speed and steering angle to localize the sensors

 

Location doesn't work with one point of reference. Do you have factory nav?

 

the tpms has nothing to do with the nav, the tpms system uses the wheel speed sensor at each wheel and the steering angle to tell the system where the tire is located on the vehicle because the inside tires turn slower when making a turn

 

You and I are talking two different things, my fault, sorry.

I thought you were talking about the underdash tpms button. But you're talking about a menu option in Nav.

That option only calibrates Nav. (The nav computer does use wheel speed for some things, like calculating mileage and whatnot). It does not calibrate the speedo. Admittedly this next part is speculation, but allowing and encouraging the speedometer to be tampered with by the end user would make open season for massive lawsuits. I can't imagine the Toyota legal team being that dumb.

 

I thought about ‘how could this work’ and I suppose it’s possible there is some witchcraft black-magic in the Nav head unit that checks wheel speed against gps after selecting that option, and makes adjustments. Otherwise, how would it know what size or adjustment to make? But I’m still going with ‘it’s in the rounding error’.

 

SAE specs give a "range" of error on speedometers of +- 2% or so.
The reality is your speedometer is never really accurate. Your tires have different diameters based on temperature and air pressure. Your tires have a different diameter based on wear. And your tires, technically are never really rolling at the exact same rpm because of the variables listed above plus the inside or outside turning radius.
So, the only true way to get an actual accurate speed the only way is thru gps comparing relative speed.
Don't know what you guys are adjusting but it is not the speedometer and odometer. That is illegal.

 

This has been common amongst most MFG's for ever. It has been documented in many magazine car test articles. Is it because of MPG reporting?

 

If the odometer were off too, then one could argue it would clock more miles than reality and burn through mileage warranty faster. Speculation only.

 

Let me rephrase the question and request people only respond if they actually have done this.

Has anyone WITH larger tires, ideally 33'+ AND factory navigation seen the tire change setting in the navigation correct the digital speedometer readout in the dash?

 

It wouldn't be black magic. If speed is registered at the wheels then the sensor counts the rotations and when the rotation hits a set number, let's say 60,000 then it knows the truck has done one mile. If Toyota programmed the navigation to have the nav report the time it took to drive one mile and recount the number of rotations then the original count of 60,000 could be reduced to 50,000 with larger tires. Now the truck is just counting the number of wheel rotations to determine if it hit one mile.

 

Pretty straight forward, ‘witchcraft’ is my lingo for all things blackbox. Lol.

 

It does nothing. I tried the calibrate from nav settings with 33s. After a couple weeks it is still off. In the owners manual it states that the calibration in the nav is to fine tune exact location on the map.
It has nothing to do with the instrument cluster.

 

I still have stock tires so I haven't tried. But assuming it does affect the digital speedometer while not affecting the analog dial, do you see a difference in the reported speed between the two? I think that would answer your question.

 

It doen't fix the speedometer!