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Tire Rotation Question. . .
- Thread starter jkdman123
- Start date
Dolemite
is my name
linux-works
Active Member
I'm guessing - but I doubt its signal strength based. the tool that assigns them to locations makes much more sense to me.
each one would have a unique id; but rssi is not going to be enough to discrim between them (again, just an educated guess).
if that is true, there is no way for them to 'auto configure' themselves, in terms of locations. they all should show up and report values, but they will be at the wrong phys locations on the 'car body map'
each one would have a unique id; but rssi is not going to be enough to discrim between them (again, just an educated guess).
if that is true, there is no way for them to 'auto configure' themselves, in terms of locations. they all should show up and report values, but they will be at the wrong phys locations on the 'car body map'
destructure00
Active Member
I've rotated several times and never had to reset positions. Never tried right after rotating to see how quickly it updates but any time I've changed tire pressures (1-2x a month) the correct one updates on the display.
Ugh. So if you wanna rotate your tires yourself, you need to have the TPMS tool to make everything copacetic again?? I was thinking of doing the first rotation myself. But then I thought about this.
It’s not necessarily a show stopper, because if I get an alert and it’s not obvious which tire is low I’d just check them all to find the bad one, but I’d like for the display to be accurate.
linux-works
Active Member
well, here's an idea for tesla: provide a 'calibrate' or 'setup' sub-gui, in a maint user-mode, and let users assign them to locations or check/validate them.
not sure how to give feedback, though. for stuff where you define mappings of {phys, logical} you often will select a logical entity (tree widget, etc) and do a 'blink for me' or something that can indicate which thing is being selected.
how does that happen via the tool, btw? if all 4 are mounted, you can't power them down, they are already inside the wheels, right?
is there a beeper (piezo) for each one, by any chance?
not sure how to give feedback, though. for stuff where you define mappings of {phys, logical} you often will select a logical entity (tree widget, etc) and do a 'blink for me' or something that can indicate which thing is being selected.
how does that happen via the tool, btw? if all 4 are mounted, you can't power them down, they are already inside the wheels, right?
is there a beeper (piezo) for each one, by any chance?
destructure00
Active Member
I really don't think this is true. When swapping a different set of wheels the car learns them automatically, doesn't need to be told what corner they are on. Why would it be any different on a rotation?
linux-works
Active Member
I'm now curious 
you can tell the fronts from the rear, over time. how? rears always rotate the same amount (give or take a little, left to right), but as you turn, your fronts may slip more and not rotate as many times. the 'tick' counter on the wheels may be able to tell this. the car will know when the steering is not straight (the time that the wheels might slip a bit).
so, thinking about it more - maybe from observed behavior, it could determine a lot.
if the rssi receiver is on one side of the car, that might be enough to tell left from right; and I think I've convinced myself that I can tell front from rear, with enough driving patterns.
yes/no? what do you guys think?
you can tell the fronts from the rear, over time. how? rears always rotate the same amount (give or take a little, left to right), but as you turn, your fronts may slip more and not rotate as many times. the 'tick' counter on the wheels may be able to tell this. the car will know when the steering is not straight (the time that the wheels might slip a bit).
so, thinking about it more - maybe from observed behavior, it could determine a lot.
if the rssi receiver is on one side of the car, that might be enough to tell left from right; and I think I've convinced myself that I can tell front from rear, with enough driving patterns.
yes/no? what do you guys think?
destructure00
Active Member
If this post is to be believed, there's individual receivers for each tire.
TPMS programming | Tesla
TPMS programming | Tesla
linux-works
Active Member
4 receivers is an obvious first-idea solution, but it COSTS.
my idea uses just 1 receiver and I think the rest can be implied.
(hope I didn't just give a patentable idea away for gratis, lol)
my idea uses just 1 receiver and I think the rest can be implied.
(hope I didn't just give a patentable idea away for gratis, lol)
puckpurnell
Member
I had Tesla road service rotate my tires last fall. Tech said, "Let's take it for a drive and see what the sensors say." So we did and there was no problem. He was satisfied and so was I.
linux-works
Active Member
how did you *verify* that the upper left is really that tire? yeah, you can see 4 levels - but how do you know A means A and not B, C or D ?
Dolemite
is my name
As far as I can tell, it looks like there's only one TPMS module in the car itself. I thought there was one receiver on each corner, but it looks like I was wrong:
17-19 Tesla Model 3 Tire Pressure Monitor ECU Module Unit TPMS 1118580-00-D | eBay
If this is the case... I'd love to know how the hell it knows outside of using that stupid handheld computer. As someone else mentioned above, the car could be tracking wheel rotational speed? Although I'm not sure if the individual TPMS sensors are that capable/complex?
Or... could each transmitter be sending two signals - one that says "hello, I am X. I will be sending you a second signal in 400 ms." When the signals arrive at 402 ms, 410 ms, 440 ms, & 450 ms, maybe then the car knows the order from closest to furthest, since the TPMS module is offset relative to the central point of the car?
Someone figure this out pls
17-19 Tesla Model 3 Tire Pressure Monitor ECU Module Unit TPMS 1118580-00-D | eBay
If this is the case... I'd love to know how the hell it knows outside of using that stupid handheld computer. As someone else mentioned above, the car could be tracking wheel rotational speed? Although I'm not sure if the individual TPMS sensors are that capable/complex?
Or... could each transmitter be sending two signals - one that says "hello, I am X. I will be sending you a second signal in 400 ms." When the signals arrive at 402 ms, 410 ms, 440 ms, & 450 ms, maybe then the car knows the order from closest to furthest, since the TPMS module is offset relative to the central point of the car?
Someone figure this out pls
linux-works
Active Member
it would not be the tpms that tracks the wheels, but usually (well, for some cars I'm familiar with) its a hall sensor.
even though cars have gps, gps sometimes fades and fancier gps modules can do dead reckoning, to more or less degree. having wheel tick sensors enables that, along with the IMU sensor array in that kind of advanced gps module.
(ob disc: an area I worked in, lol)
even though cars have gps, gps sometimes fades and fancier gps modules can do dead reckoning, to more or less degree. having wheel tick sensors enables that, along with the IMU sensor array in that kind of advanced gps module.
(ob disc: an area I worked in, lol)
linux-works
Active Member
oh, seems we have confirmation that its just one sensor. and its also on one side of the car.
hmmmm.....
guess I don't get my patent money afterall.
hmmmm.....
guess I don't get my patent money afterall.
linux-works
Active Member
my guess is that each one has a UUID (like a mac addr) and it uses that to advertise the pressure values.
On most modern vehicles, TPMS system consists of four (4) sensors in tire valve stems, three (3) receivers on the chassis that monitor the four wheel sensors, and the central Control Module (CM).
Only three (3) chassis sensors are needed because the fourth can be skipped for cost savings reasons as CM relies on the process of elimination to determine the fourth wheel's location. This is the industry-standard configuration for 433 MHz TPMS systems. Tesla uses 433 MHz system and sensors, which are interchangeable with those you can buy online.
Each of the wheel sensors have a unique ID that is recognized, registered and recorded at the beginning of each drive. That's why the pressures are not displayed until 10+ seconds after you start driving. Afterwards, pressure and air temperatures can be displayed as RR, LF, LR, RF, or via color-coded graphics, or what not.
Sensors don't broadcast until the wheels are spinning, to save battery life.
Once they start broadcasting, all nearby vehicles an in-road sensors can detect the signal. But CM will only monitor and display data from the sensors it had self-initialized for at the start of the drive.
No, you do not.
HTH,
a
P.S.: Some TPMS systems use one (1) chassis receiver, mounted off center, to deduce which wheel sensor was on which corner based on the difference in the strength of the signal. But that's less reliable, as sensors' batteries weaken at non-linear rate.
P.P.S.: There is also indirect TPMS, which monitors ABS wheel speed sensors. If one tire pressure is low, that wheel will rotate with greater frequency that ABS sensors will pickup, and trigger the "low tire" warning. However, it won't know the exact pressure, only that one tire's pressure is lower than that of the other tires.
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linux-works
Active Member
a lot of car design is about cost savings.
A LOT.
I speak from experience
and so, the 1 receiver method makes way more sense since the car has SO much smarts in it, doing some small calcs and signal level tracking (battery degredation in the sensors) they can know which is where.
as you said, dumb cars need more receives and that does make sense.
I do believe that elon would not accept a 3 rx solution if 1 can be done with some software magic
A LOT.
I speak from experience
and so, the 1 receiver method makes way more sense since the car has SO much smarts in it, doing some small calcs and signal level tracking (battery degredation in the sensors) they can know which is where.
as you said, dumb cars need more receives and that does make sense.
I do believe that elon would not accept a 3 rx solution if 1 can be done with some software magic
Model 3 is fitted with a Conti TPMS controller which utilises a coded HF signal from each sensor.
Each sensor sends ID, pressure AND direction of rotation. This is used to derive which side of the car the sensor is on. Signal strength is used to derive which end of the car the sensor is on. Hence the controller is located between rear wheels to provide different signal strengths from front and rear. This combination allows the correct wheel to be identified without any driver input or recoding after rotation.
Each sensor sends ID, pressure AND direction of rotation. This is used to derive which side of the car the sensor is on. Signal strength is used to derive which end of the car the sensor is on. Hence the controller is located between rear wheels to provide different signal strengths from front and rear. This combination allows the correct wheel to be identified without any driver input or recoding after rotation.
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