Any ideas about what causes a false low pressure reading. Quick story, my wife goes to work this morning, almost there, the light on the dash comes on showing a tire is down. She looks at computer screen and it says all tires at 41-42 psi. She gets out and checks and they all look fine. After work she runs over to Discount Tire, which is right around the corner and where we bought the tires 10,000 miles ago. The guy there resets the tpms and says we have too high a pressure. He says it should be 35 psi, I always run what the sidewall says, 44psi. She drives a 2008 Nissan Pathfinder and we have never had a problem with the pressures being "too high". Two questions: is this a common problem( too much pressure)? And is it wrong to run a tire at the pressure listed on the side wall? My wife likes the ride at the higher pressure.
42psi is high enough to trigger the TPMS. Generally the high trigger is 42 and the low is 26.
The TPMS isn't just a flat tire warning, it's an incorrect pressure warning. If you're cranking up the pressure, you're possibly making it unsafe.
10% of the door tag pressures trigger the light, IME. So if it is 30 psi, 27 or 33psi will trigger the light.
Ranger50 wrote:
10% of the door tag pressures trigger the light, IME. So if it is 30 psi, 27 or 33psi will trigger the light.
I think it must be more than that. The 4Runner door tag pressures are 32psi, But the light doesn't go on until the tires (including spare) get down to 25. And I've had the rears up to 39 when doing heavy towing and had no light.
10% variance can practically be achieved if you take the car out of the garage in the winter and go drive around in 10 degree weather, or if you are carving up a mountain road in a sportscar :)
Thanks for your quick responses. I understand about sidewall stamping being the max but always thought that for the street it would work fine. I will drop the pressures and see what happens, wife didn't like the ride at 35. Maybe 38? Our last set of tires were from the factory and never had a wear issue, even after 60,000 miles. I do rotate at every oil change. Thanks again,
In reply to irish44j:
This is from working on GM and Chryslers at the time. So, YMMV.
But seriously, it gets old when the temp drops 10 degrees and the "Tire light is on." RO's..... And it was about 10% of the door sticker every damn time.
OEM tire pressures are often on the low side for ride and handling reasons, so a little overinflation is often beneficial for tire wear purposes.
I hope I didn't come across as brash/insulting with the unsafe comment. They need to draw the line somewhere to turn the light on, and I still see plenty of people who pay 75 cents at the air hose and by gum, they're going to get their 75 cents' worth, and they end up with 90psi in their tires. Or more. I had one Maxima peg a 120psi gauge.
No problem. You guys know your stuff better than I with all your experiences. That's why I asked. ;D thanks again
i like the idea of sealing all the TPMS dealies in a pvc pipe that is inflated to whatever the proper pressure is and throwing it in the trunk...
novaderrik wrote:
i like the idea of sealing all the TPMS dealies in a pvc pipe that is inflated to whatever the proper pressure is and throwing it in the trunk...
I've head this method only works on older TPMS sensors, as the newer ones are "turned on" only when they sense wheel rotation. Just what I've "heard" though. I know a couple 4Runner guys who tried to do this and were unsuccessful, but YMMV.
irish44j wrote:
novaderrik wrote:
i like the idea of sealing all the TPMS dealies in a pvc pipe that is inflated to whatever the proper pressure is and throwing it in the trunk...
I've head this method only works on older TPMS sensors, as the newer ones are "turned on" only when they sense wheel rotation. Just what I've "heard" though. I know a couple 4Runner guys who tried to do this and were unsuccessful, but YMMV.
yet another reason to not own anything built in the last decade or so.. if it doesn't have a throttle cable but does have tire pressure sensors, then it's too new..
if the "throw them in the trunk" doesn't work anymore ... how do you handle aftermarket wheels .. do the sensors transfer easily ?
Sensors transfer pretty easily.
wbjones wrote:
if the "throw them in the trunk" doesn't work anymore ... how do you handle aftermarket wheels .. do the sensors transfer easily ?
I transfer sensors on a daily basis. Only vehicles I ever have trouble with are some new GM trucks. Sometimes they won't reset properly when using the Snap-On tool.
OP, yes, you can have too much pressure in your tires and it throw the TPMS light. You should go by what the door placard says.
Not all SUVs has a sensor in them, that is a Toyota/Lexus thing. In most of their cars and trucks.
Pbw
New Reader
9/5/13 7:15 a.m.
My wife has an at&t labeled USB phone car charger and if connected to the cigarette outlet it trips the tpms warning light of our Honda and KIA. Just a thought.
Perhaps all TPMS sensor are not the same.
I ran my rear tires at 42 psi. on my 2013 Fiesta. No light.
Suggested is 32 psi.
This was just for an autocross experiment.
Although I drove them 50 highway miles.
Ok one last question: if the tag says 35 psi but you put on different tires, wouldn't they possibly require a different pressure thus making that recommendation moot? I understand that if I put on tires on the factory rims and roughly the same size they probably have a similar build and I'm probably answering my own question, but just wondering out loud...this seems like a no brainer but...
the last set of tires I was running (aftermarket wheels no sensors) I liked having 40 psi on the front, 35 rear. door says 32psi all around.
about to put new tires on the oem wheels (with sensors) ill see what happens. would be nice to not have those lights on the dash anymore.
piece of black electrical tape ...... 
Iusedtobefast wrote:
Ok one last question: if the tag says 35 psi but you put on different tires, wouldn't they possibly require a different pressure thus making that recommendation moot? I understand that if I put on tires on the factory rims and roughly the same size they probably have a similar build and I'm probably answering my own question, but just wondering out loud...this seems like a no brainer but...
This is why any reputable tire retailer will look up the specs for your specific vehicle. They have a load rating listed after the size, this will help get consistent characteristics for new tires.
I usually run at least a couple psi higher than the door sticker for better handling and MPG.
Cone_Junky wrote:
I usually run at least a couple psi higher than the door sticker for better handling and MPG.
To the OP's second question, ^^^this is what I typically do on cold tire pressure even with a different tire size. We change tire sizes all the time. Hell, I think we put a ratio of 10/1 different size to OEM size.
Only time I stray far from the door placard:
-If we are putting mud terrains on a truck that calls for 30 psi and I usually run 35+ psi.
-If we are putting a tire that isn't rated high enough. This is usually with HD trucks that we are putting mud terrains on that call for 80 psi in the rear. Mud terrains are usually rated up to 65 psi. This usually cause no issue with the TPMS.
-Stretched tires that are so prolapsed you can see the barcode on the bead as the bead is "seated". I run no less than 40 psi.
wbjones wrote:
if the "throw them in the trunk" doesn't work anymore ... how do you handle aftermarket wheels .. do the sensors transfer easily ?
You get sensors installed in the new wheels. I know that Tire Rack will do this for you. They are coming down in price. There are generally only two flavors of sensor, 315MHz and 434MHz, and you can get them for snap-in sensors instead of the thread-in. Separate sensor and valve. The snap ins are far far better because they don't corrode or get damaged as easily, so we install those whenever we can. It's still a couple hundred bucks for a set of sensors but this is far cheaper than it used to be, and they are only getting less expensive.
What you have to do after that will depend on the car. Usually, Japanese cars need all of the sensors logged in a reader tool, which then programs them to the car's computer. Late-model Fords are the opposite - they will self-learn new sensors or new sensor positions, often within two rolling diameters!
Another thing you can do with aftermarket sensors is clone the existing sensors' ID codes. That way there is no relearning involved when you swap wheels. As far as the car is concerned, you didn't change a thing when you swapped wheels.
An aside - I want TPMS in all of my cars. It's a pretty nice thing to have, especially if you get the kind of system with a pressure display instead of an idiot light.
I am probably going to run them around 38 psi, door says 35 but wife says its too " squishy" :)
wbjones wrote:
if the "throw them in the trunk" doesn't work anymore ... how do you handle aftermarket wheels .. do the sensors transfer easily ?
I handle it in the simplest, most sensible way possible.
scissors, small piece of electrical tape. Pop the cluster hood off, pull off the clear panel (usually held on with little clips around the edges), put tape over light. Done.
shows up in a camera flash, and occasionally in direct sunlight (though sunlight really doesn't get this far into the gauge cluster), but 98% of the time it's totally invisible.
I used to use matte trim tape (which was nearly invisible even with a flash), but I ran out so just used electrical tape this time.
