Does TPMS tire selection calibrate speedometer?

[Marius A]

Will changing the tire type in the "reset tpms" screen also recalibrate the speedometer?
If yes, then would it also be true that as long as the wheel diameter is the same then the speedometer accuracy will stay the same?

If both of those are yes, then selecting the Track Pack 20" from the TPMS sensor would mean there's only a 0.75% diameter difference if you want to put 255/45/18 tires on your car, but if it doesn't reset then there's a 1.86% difference instead.

 

[dfwatt]

Will changing the tire type in the "reset tpms" screen also recalibrate the speedometer?
If yes, then would it also be true that as long as the wheel diameter is the same then the speedometer accuracy will stay the same?

If both of those are yes, then selecting the Track Pack 20" from the TPMS sensor would mean there's only a 0.75% diameter difference if you want to put 255/45/18 tires on your car, but if it doesn't reset then there's a 1.86% difference instead.

No it does not reset the speedometer. The speedometer at least by radar calibration is about a mile an hour optimistic at highway speeds so a slightly larger Tire actually puts its spot on

 

[SSedan]

Don't reference wheel diameter and speed unless you are driving around without tires.
Why would TPMS recalibrate speedo? Telling the car it has a different tire/wheel package will just have it reset to that tire diameter.

 

[Marius A]

No it does not reset the speedometer. The speedometer at least by radar calibration is about a mile an hour optimistic at highway speeds so a slightly larger Tire actually puts its spot on

Talked to a Tesla SC worker, he said that selecting a different rim in the TPMS reset screen would adjust the speedometer accordingly. The 19" is smaller than the 20", and the 18" even smaller, so it's not unreasonable to think that selecting rim type would not only reset tpms but also make a minor speedometer adjustment.
He was going to escalate the request for me to see if he got a definite answer.

 

[dfwatt]

Talked to a Tesla SC worker, he said that selecting a different rim in the TPMS reset screen would adjust the speedometer accordingly. The 19" is smaller than the 20", and the 18" even smaller, so it's not unreasonable to think that selecting rim type would not only reset tpms but also make a minor speedometer adjustment.
He was going to escalate the request for me to see if he got a definite answer.

It's possible but given that the differences between the stock wheels and tires ( 235/ 45 - 18, vs 235/40 - 19, vs 235 / 35- 20) is less than 1% in terms of rolling diameter, I'm not clear there's much margin in that. 1% is generally considered the lower end of speedometer error anyway. Lots of cars are 1% to even 3% optimistic

 

[Sophias_dad]

I'd think it would be trivial to test this yourself, without changing tires.

 

[Marius A]

It's possible but given that the differences between the stock wheels and tires ( 235/ 45 - 18, vs 235/40 - 19, vs 235 / 35- 20) is less than 1% in terms of rolling diameter, I'm not clear there's much margin in that. 1% is generally considered the lower end of speedometer error anyway. Lots of cars are 1% to even 3% optimistic

Sure, but you can select he track pack tires from the screen which are just shy of 2% bigger than the stock 18"

I'd think it would be trivial to test this yourself, without changing tires.

How?

 

[Sophias_dad]

How?

Find a section of highway with mile markers, around here most highways are marked every 0.2 or 0.1 miles.

Set the wheel selector to 18" aero, you don't need to wait for them to the TPMS sensors to connect. As you drive by a convenient mile marker, reset one of your trip odometers to 0. Drive N miles(the longer the better, but a few miles should be plenty), staying in the same lane, although speed shouldn't matter. When your trip odometer flips to N miles, you should be pretty close to a mile marker. Make note of how far away(before or after, but you'll likely be just before the N mile marker.)

Reset the wheel selector to 20" or 19" and repeat the above, using the same lane. Chances are good you'll be a different distance from the N mile marker.

This would be far easier with Dragy or something else with GPS speed display with a tenth or hundredth of a mph display(with accuracy). Maybe there's a phone app around that does it, but I'm not so sure about their accuracy.

 

[KenC]

Just noticed ABRP today, has a line where it tells you the difference between your speed displayed and actual speed. Good to know after you put on snow tires.

 

[Marius A]

Find a section of highway with mile markers, around here most highways are marked every 0.2 or 0.1 miles.

Set the wheel selector to 18" aero, you don't need to wait for them to the TPMS sensors to connect. As you drive by a convenient mile marker, reset one of your trip odometers to 0. Drive N miles(the longer the better, but a few miles should be plenty), staying in the same lane, although speed shouldn't matter. When your trip odometer flips to N miles, you should be pretty close to a mile marker. Make note of how far away(before or after, but you'll likely be just before the N mile marker.)

Reset the wheel selector to 20" or 19" and repeat the above, using the same lane. Chances are good you'll be a different distance from the N mile marker.

This would be far easier with Dragy or something else with GPS speed display with a tenth or hundredth of a mph display(with accuracy). Maybe there's a phone app around that does it, but I'm not so sure about their accuracy.

Now I feel dumb, didn't even consider the odometer