Can someone explain why individual TPMS reporting would've been so much more work?

Can someone explain why individual TPMS reporting would've been so much more work?

I'm not a car tech guy but figure by logic that the Model S has to have individual tire pressure sensors in order to trigger the TPMS warning. So why not simply step it up a notch and tell you which tire is low? I'd love to know what the massive undertaking would've been, or if this is just one of those things they didn't get to...

Captain_Zap | 19 novembre 2013

What makes you think that your car will not be getting that in the future? They are prioritizing their roll out.

john | 19 novembre 2013

I never mentioned that, would be great to get in a roll out. Just looking to understand the "technology time" difference, if you will, between installing a TPMS system and installing it with individual reporting...for my own education. :)

jat | 19 novembre 2013

My guess is the car doesn't keep track of which tire is mounted on which wheel, as that would require updating when you rotate the tires.

For example, when I had the TPMS switched over to my track tires at the service center, it was reading the TPMS on the tires that were inside the car just fine, and never complained about them not being mounted. If it can't tell tires mounted from tires inside the car, it can't tell which tire is mounted where.

So, just giving you 4 tire pressure numbers and not being able to tell you where they were is only marginally more useful than just saying a tire is low. However, even that would be useful in deciding whether it is just slightly low due to cold or if there is a real problem before driving a couple of miles or getting out and looking at them, so maybe they could make the message give the lowest read pressure and not say what tire it is on.

chrisdl | 19 novembre 2013

Each TPMS sensor transmits a unique ID over RF. Therefore, it only requires a software update where you can indicate which sensor is installed for each wheel. (Currently you can only specify a "set of four" sensors for all wheels at once.) Once each sensor and the wheel it belongs to are identified, the car can then show individual tire pressure for each wheel.

I expect Tesla to implement this is in the future. In the meantime, you can vote for this feature on Teslatap or in the prioritized software list on this forum.

Wayne3 | 19 novembre 2013

Couldn't they do something more automatic? I would guess that the pressure in a tire varies as you drive. I'm not sure how sensitive the measurement is, but if it's accurate enough, this could be used to tell which reporting tire is which as you drive. A right turn, for example would tend to put additional pressure on the left tires. A stop would tend to put additional pressure on the front tires. Since the car knows when it is turning and stopping, it could use the tire pressure fluctuations over a few minutes of driving to calibrate which tire sensor is which.

jat | 19 novembre 2013

@chrisdl - yes, but I suspect the center console computers have very limited access to the CAN bus for the car, so you are talking about firmware changes to safety-critical portions of the car to allow access to writing to the TPMS controller. Those changes are going to be more conservative and take longer, and there are lots of things I suspect are considered higher priority, particularly considering they just added the Reset TPMS button which addressed the #1 TPMS-related need (and saved them money of having owners bring their cars by the shop to swap tires).

Also, the UI for such a feature is awkward -- assuming that owners didn't write down the TPMS sensor ID while the tire was unmounted, how do they tell which tire is mounted where if the radio receiver can't distinguish the mounting locations? The way you do this now is to have a reader which triggers the sensor and reads the ID (and the range is great enough when the service center switched to my track tires, we had to take them out of the car so only one would trigger at a time), and then you feed those IDs to the TPMS controller via the ODB2-like connector behind the cubby.

I do suspect that it will happen, I just wouldn't expect it to happen anytime soon.

elguapo | 19 novembre 2013

FWIW, I asked this question at my local service center a month ago and was told the car does have the ability to read pressure on all wheels separately and a future software update will provide the info. They are just prioritizing and working on the graphics for it, etc is less important than other updates (like nave).

chrisdl | 19 novembre 2013

@jat: You bring up valid points.
Adding a wheel by wheel TPMS configuration and view would mainly comprise building a nice UI and some control logic to support a manual procedure to identify each wheel (deflate tire or use a magnet to identify sensor). We know that Tesla can make nice UIs, so I'm not too worried about the software complexity. I'm not sure if they want to add such a procedure to an otherwise minimalistic car, but I personally would like to have it.

jat | 19 novembre 2013

@elguapo - each sensor reports its own ID, pressure, and temperature, so that isn't the problem -- the problem is telling which sensor goes with which location on the car. | 19 novembre 2013

My Lexus LS460 would show the tire pressures, including the spare tire, but did not tell you which tire was in what position. You just got 5 numbers. Better than nothing, but also somewhat annoying.

GM came up with a clever system (if I remember correctly) to identify a sensor with a specific tire. You went around the vehicle letting some air out of each tire in sequence, and it beeped when it recognized the pressure change and identified that sensor. Of course you had to add back in air to complete the process, but it wasn't too bad. You had to redo the process when you rotated the tires or changed them. I suspect the dealers hated the extra time/effort required (or they just passed the cost onto the consumer at a nice markup).

Some manufacturers have a sensor pickup by each tire, so they know which tire is associated with the sensor, but this is more expensive, and is rarely done. Not something that could be retrofitted.

carlk | 19 novembre 2013

My Porsche reports individual tire pressures. It has a reset function to identify the tires when tire positions got messed up. It takes a few minutes to finish the resetting. I don't know how that's done though.

Alex K | 19 novembre 2013

@carlk | NOVEMBER 19, 2013: My Porsche reports individual tire pressures. It has a reset function to identify the tires when tire positions got messed up. It takes a few minutes to finish the resetting. I don't know how that's done though.

Porsches have TPMS receivers near each wheel well and can tell which tire's pressure they are reading. It's a real handy feature:

Captain_Zap | 19 novembre 2013

What happens when you rotate the tires? How does that work?

I got a screw in my tire on Sunday. The car warned me that my tire pressure was very low and it told me to pull over. (I was already parked at a Supercharger when the alarm went off.) I used a $2 tire guage and found that one of my tires did have low pressure and then I noticed the screw in between the tread.

I used the Tesla inflator with the goop option turned off and it got the pressure up over 40 pounds. It wasn't losing pressure rapidly and so I went to a tire shop that was half a mile away.

The tire shop was impressed with the Tesla air pump because it was strong enough to take the tire over 40 pounds. I got the tire fixed and I was on my way.

Out4aDuck | 19 novembre 2013

I'm sure that Tesla will have this feature soon. Still, it's surprising that they launched without it. My 7 year old car displays individual pressures. And yes, you have to deflate in sequence if you want to re-learn the tire position.

MandL | 19 novembre 2013

Funny. A guy at the service center told me they haven't yet because in the system it's recorded in millibars instead of PSI. I didn't push, but I think that change is just a simple multiplication factor.

jat | 19 novembre 2013

Personally, I would rather not have individual tire pressures than to have to let air out and pump it back up - I can check the pressures myself with a gauge if it isn't noticeable visually.

Captain_Zap | 19 novembre 2013

When my tire was "very low" I couldn't tell by looking at it.
I have the 21" wheels on it now so I wouldn't have suspected anything without the alarm. Honestly, I thought that the alarm was a bug because it was my first drive after the update. I had a false TPMS warning after an update a long time ago.

Yes, it would have been nice if I knew right away with an indicator. It would have meant a few less minutes in the rain trying to find out which tire was low. I'm happy that the car gave me a message to pull off the road safely before I had a bigger problem.

RanjitC | 19 novembre 2013

Wow I didn't realize how much stuff goes into a simple TPMS display in the Porsche. I did get annoyed that when the TPMS went off in my model S I had to check all the tires. Well I hope the fix does come along eventually.

riceuguy | 19 novembre 2013

There may also be some issues around the multiple vs. single antennas. I believe the service center said that I had one central antenna but when I had major TPMS issues the final fix was to put an antenna by each wheel, which implies that at least by VIN 83XX they were still using one antenna, not four.

carlk | 19 novembre 2013

Yes you don't know how nice it is until you got used to the individual pressure display. No you don't need to let out the pressure to reset TPM in the Porsche system. For other systems it's probably only when you do tire rotation which shouldn't be a big deal.

chrisdl | 20 novembre 2013

You don't actually need to let air out of each tire to match the sensors. It's sufficient to hold magnet next to the valve. (If you have a magnet handy.) That'll also trigger the sensor.

Dramsey | 20 novembre 2013

Are you guys sure that the Mod S even has individual sensors on each wheel?

I've seen three different TPMS systems:

1. Rather large, individual sensors strapped around the wheel. The sensors are about the size of a deck of cards and held in place by metal straps that go around the entire circumference of the wheel.

2. Smaller, individual sensors built into the valve stems.

These sensors can report tire pressures rather accurately-- I think within 1 PSI or so-- for each wheel. Then there's the last system, which these days is the most common:

3. Using the anti-lock breaking sensors to measure the RPM of each wheel, and sound an alert when one differs significantly from the others.

System #3 is much less expensive than the others (incremental cost zero in most cases), but is also much less accurate, since you have to lose a fair amount of pressure for the system to notice. My Audi A6 uses this system. If your car has a feature whereby you can "tell" it somehow that all the tires are at the correct pressure (since it can't tell there's a problem if all tires are equally low), then this is what you have for sure.

So, how sure are we that the Mod S uses individual sensors in each wheel?

chrisdl | 20 novembre 2013

AFAIK the Model S uses system 2 with a single receiver.

In believe system 3 is currently forbidden in the USA (correct me if I'm wrong).

CarlE_P439 | 20 novembre 2013

I have been ignoring the "Tire Pressure is Low" warning when it is below freezing outside. It would be great (and too much to ask for I'm sure) if the TPMS could account for the contraction of air when it is cold!

Theresa | 20 novembre 2013

CarlE, So you want your Tesla to ignore the fact that your tires are actually low on pressure just because it is cold out? The system is reporting a low pressure because -wait for it- ta da- It really is low on pressure.

carlk | 20 novembre 2013

@CarlE_P439 That's why individual tire pressure display is useful. You could never be able to tell if the "dummy waring" is because of a few psi loss due to temperature or from real air leak.

Any Roadster owners here? I seem to remember people mention Roadsters have the real pressure display. I wonder what's the reason Tesla decided to go backwards.

Pungoteague_Dave | 20 novembre 2013

A Prius can tell you which tire is low. My F-150 pickup and BMW motorcycles can tell me the specific pressure in each tire on a real time basis. This should be doable on a hi-tech car like the S.

jat | 20 novembre 2013

@Dramsey - the Model S uses Bao Long 433mhz sensors built into the valve stem. To switch TPMS (before 5.8), you had to scan all the sensors (activating them individual with the reader) and then upload the sensor IDs to the TPMS processor via the OBD2 connector behind the cubby.

@carlk - I was talking about other systems, for cars that can't tell which sensor is mounted where, not Porsche which includes individual sensors.

@Theresa - it could calculate what the pressure would be once it is up to temperature (the TPMS sensors report the temperature inside the tire as well), and if the adjusted pressure is within the expected range then don't alert for it.

CarlE_P439 | 21 novembre 2013

Thank you At least one person understood what I was trying to say!!

Brian H | 21 novembre 2013

Air needs to be added in winter, released in hot weather. Measure after parking a few hours.

elguapo | 21 novembre 2013 I was just saying the Tesla service team told me the car has the individual sensors, there's just no UI right now to give us the info. That could be wrong, and this conversation has gone was over my head, but that's what I was told.

mvannah | 11 août 2014

At the last tire rotation at the service center, the tech noted as follows:

Concern: Tire rotation to be performed.
Corrections: Tire Rotation
-Rotated all four tires.
-Re learned tire pressure sensor locations.

I was surprised that he noted relearning the tire pressure locations and assume that it is in preparation for a software update, unless I have missed something in a prior update. Does anyone have more information on this feature? Unfortunately, I only got the note in an e-mail attachment later and didn't get the chance to ask the service center directly about the notes. | 11 août 2014

Likely the "relearn" wasn't needed, but perhaps they now do it on every rotation or the tech didn't know it's not needed?

It's mainly required if you have two sets of tires/rims/sensors - typically for winter and summer tires. When switching tires the car needs to learn the new sensors.

Checking my last rotation in February, there was no indication on the paperwork of a relearn action.

johncrab | 11 août 2014

TPMS sensors work on a passive principle developed by Leon Theremin (yes the music device Theremin). It is therefore possible to harvest a little or a lot of data in this manner by exciting the sensor in the wheel. The sensor itself has to be built around a strain gage which is built on a silicon wafer. As it deforms due to pressure, it changes its mv/v output accordingly. Matching these for uniform performance is something akin to witchcraft as the output contains some bizarre non-linearities, but using the sweet spot of its range will produce accurate readings.

Now think of a delicate piece of silicon spinning in a wheel, having centrifugal force exerted upon it in ever changing patters. Add heat, cold, vibration and stray RFI/EMI and you've got a nasty environment. Frankly, I'm surprised these things work at all and I have never seen any which were dead on. The magic comes in where the signals are processed. A car can clearly differentiate among the sensor positions since the receiver/exciters are hardwired. BUT, in order to avoid crosstalk in the RFI sigma; from one to another, they have to be "paired" with their receivers. Some makers got this phenomenally wrong (Toyota) so that each time tires are rotated, a reader must scan each sensor, then be plugged into the OBD port to upload the new sensor positions and pairing information. That's just nuts.

Proper methodology would be to start the car rolling and lock out three of the four receivers, then look for the strongest signal, pair each and affect the reset. I believe this is what Tesla does. The unique sensor signatures allow the system to ignore crosstalk, so displaying tire pressure on a MS should be a matter of writing the software to put it on the screen as Porsche has done.

I'll never trust TPMS as far as I could chuck a wheel. I've never seen an implementation that didn't constantly false or have such a deadband around the set point that it warned only when the tire was already cooked due to low pressure. It's a nice idea that someone may get right one of these days but that day has yet to arrive.

carlk | 11 août 2014

There was an old post either here or on the TMC forum mentioning the technician's screen does show individual tire pressures when the poster took the car to service the TPM. Anyone remembers this? | 11 août 2014

@johncrab - Tesla's approach only has a single receiver. This means the car does not know which tire is in what position. With more software, it can be learned, but the processes to date are somewhat cumbersome and Tesla has not implemented such a feature yet. For example, on some GM vehicles, you go through a process of letting some air out of each tire in sequence, so it knows which tire is in a specific location. When done, you have to fill all the tires again.

Some manufacturers have individual receivers near each tire, and can then identify automatically the tire's position. Some cars also display the tire pressures, but don't specify where the tire is located.

Haeze | 11 août 2014

No need to let air out of each tire to learn their positions... All Tesla needs to do is use the air suspension to lift one tire off the ground. The one sensor that loses pressure is the one it lifted ;)

Of course, this all assumes the TPMS Sensors are sensitive enough to detect a PSI change in the hundredths of one PSI, which I doubt. I just thought it would be funny.

sbeggs | 11 août 2014

and that you are among the 78% of buyers who chose air suspension. We did not, and are considering conducting an experiment to let out some of the pressure in all four tires and see what effect it has on noise, etc.

Brian H | 12 août 2014

You may get weird wear patterns; over-inflation causes "crowning", e.g.

tga | 12 août 2014 - The GM system actually works pretty well in practice. In reality, you don't need to re-learn TPMS sensors unless you are rotating tires or changing between winter and summer tires, and you probably need to adjust pressures at that point, anyway.

When I rotate the tires on my truck, I have to adjust the pressures (50 front/80 rear), so I just incorporate the re-learning into adjusting them (the system looks for a change, up or down, so bleed 2, inflate the other 2).

logicalthinker | 14 août 2014

The Volt display shows the individual tire pressures similar to that Porsche display. Volt TPMS is accurate to within a pound or so, and dynamically updates (as I drive and the tires warm up, the PSI rises. Or as I wait in the car with one side to the hot Florida sun, the psi rises.)

Individual tire pressure monitoring is extremely nice. Yes, Tesla should get around to it.... But I'm confident they will, because they will leave no roadblock that might dissuade people from going EV. <<-THAT is the reason Tesla will continually become better and better: to permanently ignore a weakness goes against their core goal: to create compelling EVs that will accelerate the world's transition to sustainable mobility.

AmpedRealtor | 14 août 2014

How about a system that automatically keeps my tires inflated to the proper pressure without me even thinking about it. Now that is something I would pay for.

Captain_Zap | 14 août 2014


That sounds like a feature that would have multiple points of potential failure or leaks. It sounds heavy too.

SeattleSid | 14 août 2014

The image of Tesla lifting one wheel off the ground, as suggested above, brings this to mind:

Which, when I think about it, might be a nice feature under certain circumstances unrelated to tire pressure.

Liam Ott | 14 août 2014

Is there an aftermarket receiver that could: (1) receive signals from the four TPMS sensors and (2) display the information similarly to logicalthinker's description of the Volt and Porsche displays?

Would it be difficult to design and manufacture such a device? | 14 août 2014

@Haeze - Very clever suggesting the air-suspension system could be used to identify tire positions. I think it might work.

@Liam Ott - I was about to say no way, but checked first. Yep, there are aftermarket systems. Here's just one:

Although it doesn't seem to identify which wheel has which pressure, you could manually figure it out.

The downside is it might require replacing the Tesla TPMS, which would show an error on screen all the time. If you were real lucky, perhaps the Tesla TPMS sensors would be picked up by the monitoring unit.

bish | 14 août 2014

Recently I was talking to the service manager in Springfield NJ about individual tire pressures being displayed on the touch screen. He told me that his computer has software that lets him see individual tire pressures. So if you get a low tire pressure warning, and you do not feel like checking all 4 tires, you can call your local SC and they can tell you which one is low. So it is just a matter of time before it is displayed on the touch screen for us.