Should TPMS report a large pressure difference between tires?

As the title states, should TPMS report a large pressure difference between tires?

I drove to work this morning and decided to take a look at the TPMS display. As you can see in the photo below, the rear passenger tire reads 7 PSI lower than all the rest. When I arrived at work, I spotted the screw that was causing issue.

But, was surprised that the TPMS system did not throw an alarm when experiencing such a large pressure delta between tires.

 

The system has a threshold based on the last reset. You just didn't hit the threshold yet.

Also, the threshold is different for each sensor as it is based on the pressure in the tire at the time of the reset.

 

Yes, but I would think the system would at least warn you that a large tire pressure delta is occurring.

 

Of course it does, exactly as I explained it. It just didn't get low enough.

It doesn't say in the Taco OM as far as I know, but for our Forester that doesn't report individual tire pressures (which I find annoying), the low pressure warning is set for a 25% pressure loss. That would have been 24psi, if your TPMS was reset at 32psi.

 

Keep letting your slow leak go and it'll set it off

 

I had on a BMW the version that would light up if the PSI fell on any given tire more than 1 or 2 PSI.

This is better.

 

Better is a bit subjective? From observation, tire temps from sun / shade and driving will cause larger pressure variations than that. I believe the rule of thumb is 1psi / 10deg? Were you getting warnings often? If not, the Bimmer system may have been a bit smarter than ours and used a rate calculation also. Of course, pressure increases while driving are normal.

Note that when looking at TS, the Taco TPMS measures to 0.01psi and also reports temperature.

My only experience on the Taco so far is airing down offroad and hitting the reset after rotating. Going from my normal 35 to 20 offroad, the TPMS trips on all the wheels as expected. I never paid attention to the pressure when they trip. I will try to remember to watch next time.

I once didn't inflate before I hit pavement. It was quite noticeable from slower acceleration and general mushiness. Of course, I'm at 35 normally because the recommended 29 is too mushy. I had good handling and perfect wear at 35 on the stock Toyos.

 

Good point. Better from a "not a pain in my ass perspective".

 

My Volkswagen was so sensitive to pressure changes that drives into the Rockies sometimes threw a warning. I much prefer a system that doesn't overreact. Warnings should be saved for actual problems so drivers don't become desensitized to them.

 

I will second this. The BMW system was way too sensitive, and therefore annoying.

I would argue that the system is "reporting", it is not "alarming". OP wants an alarm due to a delta from recent, but that's not how the system works. It will alarm with a X delta from your last TPMS reset, though so far we don't know what "X" is. If X = 10% OP may be happy, assuming his system was last reset at 32 PSI.

 

Crap! Sorry for that wall of text. I misinterpreted your post to think that the Bimmer system was better with that small range. Understood now.

 

I was driving down Texas Toll 130 between Austin and San Antonio (85mph posted) and my BMW light went off. I was so used to the finicky TPMS going off on cold days that I considered ignoring it.

I pulled over and found a fist size hole in my run flat.

I still don't understand how that happened.

Rear tire so no major curb hits.
The car ate tires so they were almost new.
I never felt anything if road debris was the cause.