Does anybody know what the overpressure psi is that activates the monitor? Thanks,
Gary S

 

I had a nail in the tire, and the monitor light was on when I got in to go home from work. The pressure was at 27psi. It was not on in the morning going to work. My guess would be somewhere around 28. Discount fixed it for free (been going there a long time with other cars.)

PS, the tire was losing around 2.5 lbs over a 24 hour period. Did not have time to take it in for a few days.

 

I think it is 4 to 5 lbs. but not sure as tiers will heat up on long hot trip so overpressure may be higher than underpressure.

 

Someone once mentioned to me that some car manufactuers don't actually check the pressure of the tire, but rather, check the level of the car itself. If one or more corners seem to fall below another corner they consider it a flat tire.

Can anyone prove or disproce this notion? I just had my rear two tires swapped and my light is on. I was thinking it might have been the difference in thread from my front tires with this, but if it actively monitors the tire pressure I will take a closer look at the tire pressure.

 

Well, if car level is what the PCM is sensing, there would be no need for the $100 valve stem/sensors in each wheel. As I understand it, the TPMS sensors in the wheels measure and communicate the status of tire pressure via a RF signal to the PCM.

 

Try not listening to people that are less smart than you are. The 8 has very expensive RFIDs in each wheel that monitors the pressure and transmits it to a central monitor.

Some cars, like Fords, use an algorithm in the anti-lock brake system to detect differences in rotational speeds to detect a low tire. If all the tires are equally low, it won't tell you anything.

You had your rear tires swapped? As in the left tire is now on the right side and the right tire is on the left? First of all, that's a no-no. The tires are directional and are made for only one side of the car. If the tires pressures are correct, the light should go out after a short distance after the TPMS re-registers itself.

 

Who swapped the tires and is it possible they let the bead of the tire break the sensors?

 

It is a local Firestone shop right next to my work. They aren't trying to avoid fixing it they asked me to come in so they could take a look. I just don't want the hassle if it is going to go away on it's own.

As far as it being possible they broke something, I always say anything is possible. How would I check something like that?

 

Don't have my book handy, but memory says that the high pressure setting is 48 psi, and the low pressure setting is 26 psi. I'll double check on my next trip to the garage.

 

The tires are directional? So, if you are to rotate tires every 5,000 miles...you just swap rear->front, front->rear...and then on the next rotation...put it back how it was?

 

I believe you are correct. Note that the range is stated in the Service Bulletin on changing tires/wheels. They also give info on how to replace tires without breaking the sensors.

I just had new Pirellis installed at a local tire place and the Mazda dealer says they broke all four sensors! Moral of the story: follow the directions!

 

Yes. And when they wear out at 15K, replace them with Pirellis!

 

About how much do the Pirellis cost?

 

Pirelli PZero Nero M+S - check out Tirerack - $150 each. I got them through Belle Tire, with mounting, balancing, sales tax and lifetime wearout ($15 ea) my total came to $848. Make sure to print a copy of the Service Bulletin on changing tires/wheels and point out that they have to remove the TPMS sensors!