I am finding conflicting information on the web. Some sites say TPMS will activate with overinflation (most sites do, actually, but a few say they will not....of those few a couple start talking about whether the system is direct or indirect. So, ORIGINAL TPMS. Had two new tires put on. Normally, before I drive away I always check the pressure and adjust to what I told them to do originally (sometimes they actually do what I tell them). So, wifey likes the tires at the factory pressure. 35 front, 33 psi rear. When I finally get around to checking early this afternoon, all tires are at 40 psi (car has not been driven for four days). But, it has been driven at least 100 miles since the new tires were put on. I am thinking the Prius does not react to overinflation?
Based on my nearly 11 years of paying attention to PriusChat posters and their experiences, I believe this is correct for Prius, all generations. I can't speak for other brands and models. But even if some do react to overpressure, 40 psi seems too low for an indication on a car with a 35/33 cold recommendation. Ambient temperatures, warming from highway speeds, and elevation changes, would trigger it much too often.
Been doing a bit more reading and am seeing that most TPMS systems seem to allow a 25 percent variance -- so, as Fuzzy1 notes -- even if they do react, 25 percent of 33 is just over 8 -- which would make the magical alarm numbers around 25 PSI and 42 PSI... Wow, 25 percent is a LOT>
Agreed ... that's why I game the system a little bit by overinflating first, pressing the set button to have it store that pressure, then letting the tires back down to the pressure I want. That way, I get the warning when they are only a little below my desired pressure, instead of a lot below. The flip side of that coin is that there's enough hysteresis in the alarm thresholds that once I get the warning, just reinflating to my desired pressure won't be enough to turn the light off right away. Sometimes it'll go off by itself a day or two later. Or I'll get impatient and run the Techstream TPMS test, which has the side effect of making the TPMS say "well, glory be, those pressures are back in range now."
I never had experience with overinflation triggering TPMS on my PRIME usually kept at 38 psi all around, but I do remember a thread someone had his TPMS being triggered by overinflation. Let me see, if I can find the thread. Edit: OK I found the thread. It was @Rob43 Maximum PSI ? | Page 2 | PriusChat
IIRC, the law requiring TPMS only requires it to warn for underinflation. It may be, but with modern tires, pressures that low can still look full on visual inspection, and that is what many people were going by, if they checked at all. Our Sable wasn't driven often, so the tire pressure could drop enough to look low, which was maybe 20psi when measured.
And I am thinking that most OEM ones don't. I recently rented a car and it rode like CRAP. Stopped by a branch of the rental company and asked them to check the tires. 3 of 4 were about 70 PSI and the 4th was 50. No TPMS light. I think that is the way they ship cars on train or truck to the dealers. Somebody at the rental place dropped the ball.......several times because the car had almost a thousand miles on it.
and - you get better mileage as well as less likelihood of hydroplaning in heavy rains. Still - ours are set so they only go up tp 50lbs after driving on hot summer streets. Gotta draw the line somewhere .
I took delivery of my car with the pressures still set for the 50PSI they like to lessen the wobble during shipping. Then I had a flat. The tire shop replaced the tire and inflated it to the factory specified pressure on the side of the door (IIRC 36). After driving maybe 4 miles, the TPWS (W for warning) triggered. Back to the shop and all tires reset. But then I had to get the TPWS internally reset to the stock settings of 36 as it seems it has to be set to the PSI of the tires. And the tire shop couldn't do it. Only Toyota online could. Now this was a Rav4h but it may have some similarity as it is a Toyota too.
Long ago, we heard that it was to prevent flat-spotting the tires during their long Pacific cruise from the factory. My 2010 arrived with 40 psi all around, and many other new Gen3 owners reported the same, at least when dealers didn't do the full PDI. Some years later, many new owners here began reporting 50 psi.
My factory to me trip was only a week. But the over-inflate to prevent flat spotting is a know trick among sports car owners whose cars hibernate during the winter.
Japan to North Carolina in just a week?? That is much faster than the normal trans-Pacific ship time to even the Pacific Northwest!
