benjiejr
Technogeekextraordinaire
I can confirm this happened to me last week too. I received a message stating that my right rear tire was low. I had gotten a small nail in it. My car is a P85D with autopilot, of course.
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TPMS - Low Pressure - Why Not Tell Us Which Tire?
- Thread starter Michael M.
- Start date
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- Driving Dynamics Model S
I can confirm this happened to me last week too. I received a message stating that my right rear tire was low. I had gotten a small nail in it. My car is a P85D with autopilot, of course.
The Roadster showed individual tire pressures. So Tesla in 2012 moved to an inferior TPMS system from what it used in the Roadster years prior? That makes little sense.
The outside temps were near 0 degrees F in Cleveland today. This made my TPMS say low tire pressure first in right front and then right rear. Once I got up and going and tire temps came up, these went off. I just wanted to confirm that the TMPS does indeed tell you which tire on a newer P85D VIN 66083/Autopilot. I also wanted to tell everyone that I use the FOBO Tire system to let me see the exact tire pressures of each tire. FOBO Tire - FOBO
Works great and its a great way to make sure your tires are properly inflated. This also confirmed that my pressures were about 38 due to the cold and then went up to 42 after driving a while.
Anyway, its a cool product, worth checking out.
Works great and its a great way to make sure your tires are properly inflated. This also confirmed that my pressures were about 38 due to the cold and then went up to 42 after driving a while.
Anyway, its a cool product, worth checking out.
Yours is the first post I have seen stating that the Model S now shows which tire is the one that triggered the warning.
Can you post a photo of what the warning display looks like?
But it still does not show the pressure of each tire? That surprises me. So you use an aftermarket system for that?
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gzerninplatz
Member
ecarfan....yeah, we use fobotire, you set upper and lower limits and it sends an alert to your smartphone if you go outside that limit - I like knowing when I'm even a couple of pounds down, lets me take care of it before it is a problem....slow leak, or even just temperature change...
Hello ecarfan,
I actually forgot to take a photo today. But I will see if its still cold enough for my P85D to show it this afternoon. It actually showed "4 tires are low" since it was -5° F this am, right where is says regen not available on the dash. I checked my FOBO, and they were at about 41 psi after driving awhile. The warning remained until I parked at work. I also think that the TPMS may be sensitive to the cold more than actual low pressure can't confirm this yet). Again the Tesla warning has nothing to do with my FOBO, as these are 2 separate things. My P85D did not give an actual pressure measurement, just "low pressure". Interesting that it told me all 4 were low this am, not sure what it will do if just 2 are low. My FOBO does the actual psi to the 1/10 of a unit. I think my tires were set to 42 psi from factory. They go up and down in temp with outside coldness and use. I've seen a range from 38 to 44 psi on all.
I actually forgot to take a photo today. But I will see if its still cold enough for my P85D to show it this afternoon. It actually showed "4 tires are low" since it was -5° F this am, right where is says regen not available on the dash. I checked my FOBO, and they were at about 41 psi after driving awhile. The warning remained until I parked at work. I also think that the TPMS may be sensitive to the cold more than actual low pressure can't confirm this yet). Again the Tesla warning has nothing to do with my FOBO, as these are 2 separate things. My P85D did not give an actual pressure measurement, just "low pressure". Interesting that it told me all 4 were low this am, not sure what it will do if just 2 are low. My FOBO does the actual psi to the 1/10 of a unit. I think my tires were set to 42 psi from factory. They go up and down in temp with outside coldness and use. I've seen a range from 38 to 44 psi on all.
The ability to show which tire depends upon the system being set up correctly. Rotating the tires without resetting the TPMS tire locations will give you the wrong indication.
Currently, there appears to be no user-accessible way to program the specific sensor ID's to specific wheels. Service centers have that capability (at least for the older subsystem), but if you get your tires rotated elsewhere, the subsystem would have the wrong location for the sensor ID that sent the alert. In addition, the "reset TPMS sensors" button appears to randomly place sensors into the TPMS subsystem "slots" for tires without regard for the tire's actual location. Of course, this is using the old subsystem -- perhaps the new subsystem is smarter and uses 4 individual wheel antennas, picking up which sensor is on which wheel with accuracy -- the old system could not.
It's even unclear whether the old subsystem could report pressures to the car's management systems. I remember a particular service bulletin that required the low-tire pressure thresholds to be programmed in the TPMS subsystem directly. It's very possible that the subsystem couldn't report the tire pressures across the CAN bus at all, and could only report that a tire was low or high or normal. Perhaps the new subsystem can, and that's why the change was made.
If you've ever done the GM "TPMS dance", you'll know how annoying assigning ID's to wheels can be from a user experience perspective. You have to do some magic sequence with light switches, key switches, door locks, and windows, then deflate or inflate the four tires in a specific order to get the car to learn the tires correctly. Then, GM took it away and required that you purchase a special tool ($60+) or take it to a dealer to assign tires to locations:
It's not as easy as it seems.
Currently, there appears to be no user-accessible way to program the specific sensor ID's to specific wheels. Service centers have that capability (at least for the older subsystem), but if you get your tires rotated elsewhere, the subsystem would have the wrong location for the sensor ID that sent the alert. In addition, the "reset TPMS sensors" button appears to randomly place sensors into the TPMS subsystem "slots" for tires without regard for the tire's actual location. Of course, this is using the old subsystem -- perhaps the new subsystem is smarter and uses 4 individual wheel antennas, picking up which sensor is on which wheel with accuracy -- the old system could not.
It's even unclear whether the old subsystem could report pressures to the car's management systems. I remember a particular service bulletin that required the low-tire pressure thresholds to be programmed in the TPMS subsystem directly. It's very possible that the subsystem couldn't report the tire pressures across the CAN bus at all, and could only report that a tire was low or high or normal. Perhaps the new subsystem can, and that's why the change was made.
If you've ever done the GM "TPMS dance", you'll know how annoying assigning ID's to wheels can be from a user experience perspective. You have to do some magic sequence with light switches, key switches, door locks, and windows, then deflate or inflate the four tires in a specific order to get the car to learn the tires correctly. Then, GM took it away and required that you purchase a special tool ($60+) or take it to a dealer to assign tires to locations:
It's not as easy as it seems.
Seems like it would be easier to just tell you the pressure of all 4 tires without the car attempting to guess which pressure goes with which tire. That way there is no need to re-learn after rotating tires.
After all, if you know that a tire is low, aren't you going to top off all four after you went to the trouble of pulling out your air compressor? Knowing the pressure in all 4 tires instead of just a warning light lets you know when they are starting to get low ahead of time so you can pump them up at your own convenience.
After all, if you know that a tire is low, aren't you going to top off all four after you went to the trouble of pulling out your air compressor? Knowing the pressure in all 4 tires instead of just a warning light lets you know when they are starting to get low ahead of time so you can pump them up at your own convenience.
OK I took some images for you.
Here is the warnings I received this am (it was very cold 0 to -5F).
Front Left Tire Pressure low.
So I checked my FOBO, and it actually looks like my front right is lowest in psi.
After running awhile the tires warmed up and the warning went away.
Here is my FOBO after warming up.
I may check to see if its actually my front right or left, maybe my TPMS is marked incorrectly or more sensitive on the left. Not sure how to remedy if the tires are miss marked on TPMS.
Hope this helps.
Here is the warnings I received this am (it was very cold 0 to -5F).
Front Left Tire Pressure low.
So I checked my FOBO, and it actually looks like my front right is lowest in psi.
After running awhile the tires warmed up and the warning went away.
Here is my FOBO after warming up.
I may check to see if its actually my front right or left, maybe my TPMS is marked incorrectly or more sensitive on the left. Not sure how to remedy if the tires are miss marked on TPMS.
Hope this helps.
billarnett
Member
It seems odd that one gets low pressure warnings were in the summer tires are simply cold. It would be very simple matter to apply the ideal gas law and compensate for the temperature.
It does, thank you and it's the first documented case of a specific tire being shown. I'm tempted to depressurize one of my tires a bit to see if my older subsystem gives a similar tire location or if I just get a tire warning..
The only way to remedy which tire is reporting is to have the service center reprogram the TPMS subsystem with the correct sensor ID's (or buy their tool that allowed you to do it yourself - early days with the Model S indicated a ~$600 cost for that tool, IIRC).
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Compensating for the temperature in measurement is not what you want to do, because if the pressure is truly low due to temperature, your contact patch to the road won't be optimal. Air pressures specified by the manufacturer are generally intended to be cold pressures at average ambient temperature. You should adjust it accordingly for conditions.
You don't want to do that. Like FlssherZ says, you want to add air to the tire to compensate for the cold weather. No wonder there are so many 21" tires that fail when they hit potholes.
Cyclone
Cyclonic Member ((.oO))
I thought that individual tire readers were only possible with the new TPMS sensors released in late 2014 with the Autopilot cars. And even then, it required a newer release (perhaps any 6.1 version). The new sensors operate on a different frequency than the old ones, so they cannot be retrofitted on older Model S vehicles unless the receiver can be swapped out too. Reports are the new sensors cost $50 each.
New production (late 2014) new TPMS sensors
New production (late 2014) new TPMS sensors
billarnett
Member
I've never spent enough time in really cold climates to have to worry about this. But it seems to me that what matters is the pressure in the tire after it gets warmed up. My (admittedly naive) intuition says that a tire will get almost as hot driving on cold freeway as on a hot one. Doesn't most of the heat come from the flexing of the tire rather than the ambient? If so, your tires will be seriously overinflated when driving if you blow them up to the sticker pressure when they're really cold. Maybe driving slowly on a snowy road wouldn't heat the tires so much. But don't you want them a bit under-inflated in that case anyway?
Roadster has individual tire pressure readouts. I doubt Tesla would have used TPMS sensors inferior to the Roadsters's.
No, No, No, No, No!
!. Heat, not pressure, kills tires. I don't know where people get the idea that putting some air in the tires is harmful--it's not. Well, fifty years ago, when we used bias-ply tires, if you put too much pressure in relative to the load, the centre of the tread would wear out quickly. Radial tires typically don't have this problem because most have a very large crown radius and the belts stabilize the tread. For almost all on-road use, you never want the pressure to be less than the vehicle placard pressure. If the day is hot you want it to be higher. If the day is cold and you inflate with indoor air you also want more pressure to compensate.
2. If you put 25 psi in one tire and 45 in another and drive for a couple of hours at highway speeds, both tires will have about the same pressure due to thermal equilibrium. However, the tire starting at 25 psi will be far hotter and may even debond. At the very least the compounds in the tire will have been substantially degraded.
3. The maximum pressure on the sidewall is for cold inflation first thing in the morning. It's not a problem (and in fact is perfectly normal) for the tire to have higher pressure after driving. Ideally the pressure increase is under 10% if the day remains relatively the same temperature, or 15% if the day grows significantly warmer. If it increases by 25% you need to find out what the cause is.
4. You never want to adjust pressure in a warm/hot tire. (This doesn't mean not adding air to a leaky tire to get to the repair shop.)
5. All tire pressure recommendations are based on a set of assumptions. One of them is that the ambient temperature is 18 C (65 F), another is that the pressure check is done cold, first thing in the morning, on every driving day. Change the assumptions and you need to change the pressure. The change is almost always upwards.
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It's not the sensors but rather the subsystem (controller) that they used. New sensors are needed with new controller because of the frequency they operate on. Perhaps the Roadster's TPMS module manufacturer was a) out of business, b) production constrained, or any other number of reasons.
I've read that some owners are able to contact service who can bring up their individual tire pressures on their computers. So the car provides the data to the mothership, it's just not being displayed to the owner. These particular owners that had posted this, if memory serves, were pre autopilot.
Then that would be squarely on Tesla. I had operated under the assumption (based on what I saw when they reprogrammed my unit for the TSB) that they had a difficult time getting that information.
Either way, though, they still have to solve the challenge of assigning ID's to wheel locations. Pushing the "relearn" button in the car and driving for a few minutes just seems to randomly fill the slots based on the 4 that are on the car.