CONTEXT for my questions...
On my weekend trip (about 240 miles each way), I picked up a small screw in the tread corner of one of my tires this weekend while at my destination. The tire shops will not repair/plug due to it's proximity to the tire's sidewall. They sprayed it down and it is not bubbling, and the full 3-1/2 hour drive back while towing a 5x8 trailer, the TPMS system revealed absolutely no loss in pressure, and the tire still sits exactly as it did before I left ofr the trip on Friday. The tire in question is in the passenger side rear position. From driving around my destination, I saw no signs of pressure loss and decided to risk the drive back without messing with either the screw or the tire until I got the vehicle home in my garage with all my tools. Just for insurance, though, before leaving to come home yesterday, I picked up a tire plug kit in the event I needed it before I got home.

At this point, I am assuming it was simply a very short screw which did not fully penetrate the tire. Anyway, while driving back yesterday, I kept a close watch on the TPMS system in hopes that I could avoid disaster by addressing a loss in pressure before the tire could go flat. While watching the system, as I would expect, I saw the pressures increase as the tires heated up from the driving. However, three of the four tires had a temperature increase of 3-5°F, while the fourth only increased 1-2°F.


QUESTIONS:

1. Is the TPM system THAT good to where I can believe these small differences in tire pressure, particularly the fact that three of the tires had one operating range while the fourth appeared to be more stable?

2. If the answer to #1 is "Yes, it's that good!", then my next question becomes whether or not the more stable tire is a result of either a failing/weak/bad sensor or it is simply a result of that tire having had a better purge and is actually running with a much higher nitrogen content?

3. What is the interpretation of tire position based on the single line display of 4 numbers (i.e DF DR PF PR, or DF PF DR, PR, etc,)?


Thanks ahead of time for your input.

 

Pete, TPMS depends on the pressure when reset. It might not have dropped to the point where it would alert you. Generally it's about a six lb difference. So if the TPMS reset button was pressed when your tires were at 35, you'd start getting notification around 29. Does it work? Absolutely. I got a nail in one of the tires about a mile from home and the pressure was dropping. But I was alerted to the situation when it hit the low side. And I was able to watch the readout. Fortunately I did manage to make it home fine. Lexus Roadside Assistance came to change the tire in my driveway. That was the first of three nails I got that year. Only one needed patching.

Re #3, there's no sequence to the readout. Some have figured out the sensor locations by playing with the tire pressure. You'd have to move up to the 4RX to get it.

 

Thanks, Anita. I'm not sure I understand your last statement, though... I'd have to "move up to the 4RX to get it." .... what exactly is the "it"? Are you talking about "it" being a displayed sensor location feature that only exists in the 4th gens, or I have to look through the 4th gen forum to find the configured sensor locations versus readout?

Also, to you comment "there's no sequence to the readout", does that mean that the sequence varies every time the vehicle is started up and it simply reports the values one-by-one as the system "connects" and "reads" the sensor output? What I observed on startup Saturday afternoon was that sometimes one sensor would lag behind the others, but it was not always the same position in the 4-number lineup which lagged, and to me, that suggests that each number location is tied to a specific sensor position on the vehicle. Perhaps I'm over thinking the situation.

 

Yes, you're right about what 'it' is. The 4RX displays the tire pressure by tire location. And it's not restricted to just the 450h I believe. I still prefer using a not so old fashioned digital tire pressure gauge though.

I can't find the thread where a few members figured out the sensor location. I believe the readout doesn't change each time you turn on the RXh. It reads as they are 'found.' Which means rarely in the same order. That's probably what you experienced Saturday afternoon. Geez, there must've been something in the air because that's when I checked my tires too Temps are starting to drop around here and it shows.

 

Well, I'm going to pull the screw out this evening and be ready to plug it right away if it leaks. Otherwise, I'll mosey over to my local Tire Engineers and have them run a full purge and refill on all four tires, and over pressure each up to about 42-44 psi. Then, once I'm home with the pressurized tires, I'll let the pressure back down to a smooth running 35 psig one-at-a-time and note which position is for which tire, and re-post that detail back here for others' convenience.

 

If the screw is right on the edge and went in sideways, it might not have penetrated the carcass and if the damage isn't too bad to the tread you might be good to go. I had a massive 3" long 3/4" wide curved spike go into the edge of my tire this summer and tore a massive gaping hole in the tread, but it didn't loose any air after removing the spike (I actually had to cut it out it was wedged in so tightly). The tire was of course ruined as the innards were now directly exposed to the road, but it drove nicely for the gentle 20 minute drive to where I got it replaced.

 

Yeah... this one will be OK if it has not penetrated. It looks like one of those short 1/2" long hex head screw (with a slot) like the ones used on electrical boxes.

Once, back in about 1986-87, I had an open end combination wrench (something like a 5/8" x 9/16") go through an almost new 31x10.50R15 tire on my '76 Jeep Cherokee Chief WideTrack. A logging truck lost one of his tool boxes right in front of me, and evidently my front tire flipped it up it must have landed right straight up as the rear tire came down on top of it... Because the wide head of the wrench went in by force but could not sling back out completely,,, I got a WHAM WHAM WHAM WHAM WHAM as it started beating my fender liner with every revolution. The guy at the tire shop had to use a big hammer and cold chisel to get it out, and when he started walking towards the back of the shop with the wrench, I had to yell out, "Hey, wait a minute. That's MY wrench. I just paid $125 for that thing (the cost of the new tire), and it's going int MY tool box!!" I can still tell you which among my hundreds of wrenches is THAT particular one! It's still the most expensive single wrench I've ever "bought". I don't think I've ever used it, but I would never part with it, either.

 

Great story, Pete. At least you got a new tire and souvenir out of the deal Just curious, how much tread do you have left on your tires?

 

Well, it actually seems as though the tire which has the screw is older than the others. All are Latitude Tour HP's, but there is noticeably less tread on the "screwed" tire. That said, I there is actually plenty of tread on all of them. The dealer records indicate that all four tires were put on at 52K miles, which means they now have 20K on them. Not sure why the one has the reduced tread depth, but the wear from side to side is even on it.

I actually chose to not disturb the screw last night since my wife needs the vehicle today. I'll unscrew it tonight, plug it if necessary and if the plug IS required, I'll just have it replaced tomorrow with a new Michelin Premier LTX (the new tire family which is replacing the Latitudes).which has better UTOG ratings while also being about $60-$70 less per tire.

 

Rode for over a week with absolutely no pressure loss. Pulled the screw last night, thinking it had not penetrated because of the ABSENCE of pressure loss. Tiny bubbles showed up in the soapy water test, though, so I plugged it as a temporary solution until I can get around to getting the new LTX on this coming week. Incidentally, the tiny bit pf pressure loss from rasping the plug hole before inserting the plug was somewhere less than 1 psi as all the TPMS values are now identical whereas beforehand, one tire sometimes showed a 1 psi higher pressure than the other three.