Tesla speedometer calibration

[Sirfun]

Since Tesla's are almost a laptop on 4 wheels, I'm wondering if there could be a mode/setting that re-calibrates Speedometer and Odometer?
With all the different wheel and tire combinations available, it seems like this would be something Tesla should do. I would think it would be easy. The vehicle could be driven in a straight line, and with GPS it could know the exact distance it traveled and calibrate the odometer. That would also make it easy to calibrate the speedometer also.
Thoughts?

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[Crissa]

Yes, there are settings for when you change tire size.

-Crissa

 

[Sirfun]

Yes, there are settings for when you change tire size.

-Crissa

Thanks for the reply. After I saw your post I decided to get off my lazy butt and do some searches for info. There are videos, but from what I've seen, the settings are only for changing between Tesla wheel & tire combinations. It changes range estimates on the computer and also changes the visual of what your car image looks like.
Also I found this to be a very complicated subject to change outside tire diameter with aftermarket wheels.
With an off-road vehicle like the Cybertruck, there will be a huge demand for changing wheels and tires with aftermarket choices. I thought with Tesla tech this could be simplified, but actually it seems with all the tech, it actually gets way more complicated.
Actually what started me thinking about this was my son asking about putting smaller street tires on the CT to lower it and improve road handling. That would be a huge difference in outside tire diameter.

 

[Crissa]

Yeah. I found out that the number of tire settings my Mazda can handle don't even deal with small differences so I'm stuck with my speed being exactly 2% wrong which is so annoying ^-^. And my winter tires are 13% wrong!

But the advantage to over the air updates is that if some setup becomes popular they can add it later.

-Crissa

 

[Sirfun]

Yeah. I found out that the number of tire settings my Mazda can handle don't even deal with small differences so I'm stuck with my speed being exactly 2% wrong which is so annoying ^-^. And my winter tires are 13% wrong!

But the advantage to over the air updates is that if some setup becomes popular they can add it later.

-Crissa

Wow, 13% that's a bunch. So at 70mph on your speedo you're actually driving 79mph? That's the kind of thing I was thinking could be avoided.
I would think the computer could calculate how many rotations the tires did to travel 5 miles on GPS and know the exact outside dimension of the tire. Also it could compare odometer distance with actual distance traveled by GPS and re-calibrate odometer. For that matter, the computer could take time and distance to cover 5 miles and re-calibrate the speedo also.
Now estimating range seems way more complicated. But after 1000 miles or more, I would think the computer could come up with averages of difference and refine it's estimates.

 

[Crissa]

Wow, 13% that's a bunch. So at 70mph on your speedo you're actually driving 79mph? That's the kind of thing I was thinking could be avoided.

It's the other way around, but yeah.

-Crissa

 

[Sirfun]

It's the other way around, but yeah.

-Crissa

Haha, oh wow so to stay with the flow of traffic you gotta drive 80-85.

 

[Crissa]

Luckiily I have built-in GPS speed in my car, but yeah.

-Crissa

 

[TheLastStarfighter]

Thanks for the reply. After I saw your post I decided to get off my lazy butt and do some searches for info. There are videos, but from what I've seen, the settings are only for changing between Tesla wheel & tire combinations. It changes range estimates on the computer and also changes the visual of what your car image looks like.
Also I found this to be a very complicated subject to change outside tire diameter with aftermarket wheels.
With an off-road vehicle like the Cybertruck, there will be a huge demand for changing wheels and tires with aftermarket choices. I thought with Tesla tech this could be simplified, but actually it seems with all the tech, it actually gets way more complicated.
Actually what started me thinking about this was my son asking about putting smaller street tires on the CT to lower it and improve road handling. That would be a huge difference in outside tire diameter.

I'm with your boy, I think the CT would look sweet with more street-focused wheels and tires. I expect Tesla to offer these in-house, and that would probably address the issue.

 

[TI4Dan]

Most modern vehicles read a speed sensor locate in the drive unit, usually a output shaft. So many pluses will indicate a wheel rotation. Now days you can program tire size and it's done.
Some aftermarket speedometers require a one mile distance driven and it's programed. I have one computer controller that has a digital speedometer that requires one wheel rotation measured in mm then number is loaded, it does not make a difference what size the wheel is and that speedometer is very accurate. I have a one bike with a digital speedometer that is off and I can't stand it. Since its a pulse type I bought a speedometer calibrator it's programmed in a percentage from 1-100% or -1-100%. The unit has a footprint of a quarter.
Small enough to fit anywhere. Some GPS speedometer are adjustable by percentage, so mile markers or known good unit to compare it to. We really should not have this problem in this day and age.

 

[ajdelange]

These modern vehicles measure the speed of each wheel separately. These speeds are compared to motor speeds in order to provide necessary input to the inverter/rectifier clocking circuits and to detect wheel slip. How these are combined to produce the displayed speed and odometer readings I don't know.

 

[Cybertruckfamily]

Why don’t modern vehicles (& the CT) just go to gps only? There must be a reason. Aftermarket hot rod & offroad speedos have gps only as a choice.

 

[ajdelange]

Because it isn't accurate enough nor reliable enough. Though this is much less of a problem today (when the "GPS" receivers also receive Glonass) there are still times when enough satellites in the right places aren't there and a velocity measurement isn't that good.

I also suspect that consumer protection laws may require that the odometer be connected to the wheels.

 

[FutureBoy]

Because it isn't accurate enough nor reliable enough. Though this is much less of a problem today (when the "GPS" receivers also receive Glonass) there are still times when enough satellites in the right places aren't there and a velocity measurement isn't that good.

I also suspect that consumer protection laws may require that the odometer be connected to the wheels.

Hmmm...... I may be vastly mistaken here but I was thinking that odometer readings were particularly used to measure the usage history of an engine. For instance, I have a family friend who exports low mileage engines out of Japan and they have to have odometer readings for each engine.

So what do odometer readings help for in an EV? Especially in cases where some EV's have separate motors that may or may not even be engaged all the time. Like in a 2 motor scenario for a vehicle that only uses the front motor if it needs to engage AWD.

I get that an odometer reading can be somewhat telling of a vehicle as a whole but if the measurement is really just a reading of how much use the engine has on it, what is the use for a vehicle that does not have an engine?

Maybe the odometer laws need to get updated...

 

[Crissa]

These modern vehicles measure the speed of each wheel separately.

The ABS computers do this separately so that they can do it quickly and without interruption. They may report this back to the central traction control but I don't know if it does. The important piece is knowing the speed between the rest of the wheels, since the speed at the motor is a straight up ratio.

-Crissa

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