TPMS question

Patrick W · Apr 22, 2015

My model S won't arrive for another few weeks (just started building it yesterday) so I don't have a tire to look at. So I'm hoping someone here can confirm or correct what I'm thinking.

From the pictures I've seen it looks like one has to remove the tire from the wheel if one wants to move the sensor to another wheel. Correct?

Thank you!

ErstD · Apr 22, 2015

Correct. The TPMS sensor is the packaged as the air valve. So you'll have to remove the tire to get to the TPMS sensor/air valve.

You can order new ones from the service center for $50 each -- very reasonable. They come in silver or black color.

HankLloydRight · Apr 22, 2015

Isn't that the case for every/any TPMS sensor?

beeeerock · Apr 22, 2015

Let me ask a related follow-up question...

If you have a second set of wheels with TPMS sensors, will the car accept them, or require a reprogramming whenever the wheels/tires are swapped?

Reason I ask is, I had a Highlander Hybrid that used TPMS and each sensor had a distinct ID code. The vehicle had 4 memory locations for these codes. When the tires were changed seasonally (second set of tires on rims), I'd have to go to Toyota and pay them to change the sensor ID codes. More cost, not to mention more hassle twice a year going to Toyota. It would have been much better if Toyota had left space for a second set of ID's and the ability to toggle between them (like telling the clock whether it should assume daylight savings time).

Patrick W · Apr 22, 2015

ErstD said:
Correct. The TPMS sensor is the packaged as the air valve. So you'll have to remove the tire to get to the TPMS sensor/air valve.

You can order new ones from the service center for $50 each -- very reasonable. They come in silver or black color.

Thanks for the confirmation. I just purchased a set of 4 wheels I plan to use with snow tires so it sounds like installing the sensors in the wheels means the regular tires and snow tires will never have to be removed from the wheels when it comes time to change types of tires.

BTW, I've never owned tires with such sensors in them. It'll be fun (at least a first

) to be cursing down the highway and to check how much pressure is in each tire.

cwave1 · Apr 22, 2015

beeeerock said:
Let me ask a related follow-up question...

If you have a second set of wheels with TPMS sensors, will the car accept them, or require a reprogramming whenever the wheels/tires are swapped?

Reason I ask is, I had a Highlander Hybrid that used TPMS and each sensor had a distinct ID code. The vehicle had 4 memory locations for these codes. When the tires were changed seasonally (second set of tires on rims), I'd have to go to Toyota and pay them to change the sensor ID codes. More cost, not to mention more hassle twice a year going to Toyota. It would have been much better if Toyota had left space for a second set of ID's and the ability to toggle between them (like telling the clock whether it should assume daylight savings time).

The console has a button to let you sync a new set of wheels. I have used separate wheels/tires for summer and winter for a couple of seasons now with no issue.

To clarify, while the car does monitor the pressure through the TPMS sensors, there is currently no display of the pressure for any of the wheels. You will just receive a warning if any wheel is outside the safe range.

beeeerock · Apr 22, 2015

cwave1 said:
The console has a button to let you sync a new set of wheels. I have used separate wheels/tires for summer and winter for a couple of seasons now with no issue.

Nice! That's the way it should have worked on the Highlander!!! Thanks!

Patrick W · Apr 22, 2015

cwave1 said:
To clarify, while the car does monitor the pressure through the TPMS sensors, there is currently no display of the pressure for any of the wheels. You will just receive a warning if any wheel is outside the safe range.

That's kind of a surprise. Seems like it should at least be able to specify which tire has the problem. And it seems like a readout of pressure in each tire should be pretty straightforward.

ErstD · Apr 22, 2015

Patrick W said:
That's kind of a surprise. Seems like it should at least be able to specify which tire has the problem. And it seems like a readout of pressure in each tire should be pretty straightforward.

The readout does say which tire (e.g., front passenger tire) has the problem (low on pressure). Unfortunately, there is no screen that shows the current pressure of each tire. This feature is commonly talked about and asked for when people talk about feature requests. Seemingly, the data is available. It's a matter of programming and UI re-design to show tire pressure data. Perhaps Tesla will include it in the upcoming version 7.0 of the firmware.

Patrick W · Apr 22, 2015

ErstD said:
The readout does say which tire (e.g., front passenger tire) has the problem (low on pressure). Unfortunately, there is no screen that shows the current pressure of each tire. This feature is commonly talked about and asked for when people talk about feature requests.

Kind of off topic for this thread but is Tesla very responsive to feature requests?

ErstD · Apr 22, 2015

Tesla introduces new features all the time. Though, I'm not sure if anyone outside of Tesla understand how feature requests are prioritized.

For example, it seems to have taken years for the valet mode to be released. And seemingly, creep mode was introduced relatively quickly after people started asking for it.

That said, it wouldn't hurt if you send your feature requests directly to Tesla via their contact page:

Contact | Tesla Motors

mknox · Apr 23, 2015

Patrick W said:
Kind of off topic for this thread but is Tesla very responsive to feature requests?

Well, I'm still waiting for iPod music controls, individual tire sensor readings, navigation map waypoints etc. etc.

I think the answer is largely "no". Tesla seems to have their own agenda on what to prioritize.

HankLloydRight · Apr 23, 2015

Patrick W said:
From the pictures I've seen it looks like one has to remove the tire from the wheel if one wants to move the sensor to another wheel. Correct?

I'll ask again -- are there *any* TMPS systems that *don't* require the tire to be removed to move sensors around? Aren't they all internal to the tire in order to read temperature and pressure?

beeeerock · Apr 23, 2015

HankLloydRight said:
I'll ask again -- are there *any* TMPS systems that *don't* require the tire to be removed to move sensors around? Aren't they all internal to the tire in order to read temperature and pressure?

Mercedes has or had a system in use that looks at tire speeds and doesn't use any sensors beyond what is likely part of the ABS system. No pressures read, obviously, but it was pretty good at noticing if a tire was low on pressure, and notifying the driver. Even to the point that I would have to reset the system after swapping winter/summer wheels... it somehow knew they were different in spite of my best efforts to put appropriate pressure in each tire. I think it saw that the relative pressures were different from the last set of tires and acted accordingly.

Having had the typical TPMS system as well, I much prefer the Benz way of doing it... especially if absolute tire pressures aren't displayed.

HankLloydRight · Apr 23, 2015

beeeerock said:
Mercedes has or had a system in use that looks at tire speeds and doesn't use any sensors beyond what is likely part of the ABS system. No pressures read, obviously, but it was pretty good at noticing if a tire was low on pressure, and notifying the driver. Even to the point that I would have to reset the system after swapping winter/summer wheels... it somehow knew they were different in spite of my best efforts to put appropriate pressure in each tire. I think it saw that the relative pressures were different from the last set of tires and acted accordingly.

Yeah, my 2002 BMW M5 has the same differential ("Indirect") system that relies on tire rotation speed (yes, part of the Traction Control system to detect slight differences due to lower tire pressure), but as the OP posted, that's not what I was asking about. It seems like he was asserting that there are real TMPS systems that don't require the tire to be removed to service/swap the TPMS sensors. It just seemed like a strange question to ask, given that all direct TMPS sensors (as far as I know) are all mounted inside the tire.

mnx · Apr 24, 2015

Yes, I much prefer the german way of doing TPMS especially since I don't need to buy a second set of TPMS sensors for winter tires.

mknox · Apr 24, 2015

HankLloydRight said:
Yeah, my 2002 BMW M5 has the same differential ("Indirect") system that relies on tire rotation speed (yes, part of the Traction Control system to detect slight differences due to lower tire pressure),

My 2007 Pontiac Vibe works this exact way. It does work, because it picked up a low pressure situation I wasn't aware of. I had thought it would be less precise than it is and it would already be obvious just by looking at the tire partially deflated.

beeeerock · Apr 24, 2015

mknox said:
My 2007 Pontiac Vibe works this exact way. It does work, because it picked up a low pressure situation I wasn't aware of. I had thought it would be less precise than it is and it would already be obvious just by looking at the tire partially deflated.

Yeah, it is a surprisingly good system. As I noted previously, it even detects when I do winter/summer swaps. If the actual pressures aren't going to be displayed and the TMPS is going to provide, essentially, 'idiot-light' functionality, Tesla might as well go with the indirect system. Cheaper and probably more reliable in the long run.

HankLloydRight · Apr 24, 2015

beeeerock said:
Tesla might as well go with the indirect system. Cheaper and probably more reliable in the long run.

It was not my intention to imply that the indirect systems do not work, just that they really don't measure actual pressure... They measure changes in tire rotation and relative differences between each tire. If all four tires were to loose pressure at the same rate, these indirect TPMS systems will not detect or report a fault (except in the case of a few specific Audi/VW vehicles).

From: http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=44

What's the Difference?

DIRECT VS. INDIRECT

Direct Systems
attach a pressure sensor/transmitter to the vehicle's wheels. An in-vehicle receiver warns the driver if the pressure in any tire falls below a predetermined level. Direct systems are typically more accurate and reliable and most are able to indicate which tire is under-inflated.

Indirect Systems
use the vehicle's anti-lock braking system's wheel speed sensors to compare the rotational speed of one tire versus the others. If a tire is low on pressure, it will roll at a different number of revolutions per mile than the other three and alert the vehicle's on-board computer. Indirect systems (except for the TPMS on several 2009+ Audi models and 2010+ Volkswagen models) are unable to generate accurate readings in cases where all four tires are losing pressure at the same rate, such as the effects of time and temperature.

mknox · Apr 24, 2015

HankLloydRight said:
It was not my intention to imply that the indirect systems do not work, just that they really don't measure actual pressure...

The fact that certain higher end Geman cars work this way aside, I always assumed this method (the ABS hack) was a poor man's version used on lower end cars and that the sensors were generally seen on higher end cars.

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