I'm planning to swap my volk rims to R95 wheels this weekend.
I was wondering how the tire pressure indicator works even though there is no tpms on wheels. is there something else i have to install inside of the tires or something??

 

It works off the speed of the tires, a tire with more air sits up higher, so the diameter is larger. The wheel speed sensors in conjunction with the ECU.

 

Thanks for explanation!

 

It is interesting that when my son had a double blow out on the freeway late last year, the TPMS light did not go on.

We know the idiot light works, we know the switch works to reset the light, just not very confident that the actual sensing works!

 

I don't know the exact logic, but it is looking for a single blowout. A double blowout might not register since two tires are both spinning at the same speed - you don't have a solo outlier. Think about it like a computer - if one speed is much different from the others, it can only mean a blowout. If two are high and two are low, the car could simply be turning (when they are on the same side) or losing traction (when they are agreeing on the same axle).

 

Because it's a relay system based on wheel speed comparisons, I doubt it would be able to react fast enough to two tires going flat immediately.

 

When you consider the software also have to accommodate when the car is in a tight turn as well, so it must not trigger false positive by monitoring the wheel RPM differences over a relatively long time. A rather low pressure tire diameter can be only minutely different from a properly inflated others. This low tech dumb AI is too overrated especially from the turn of the the century. As the software has no knowledge of what wheel diameter you use, it determines a baseline average from all 4 wheels.

 

From the owners manual:
"The Flat Tire Monitor cannot alert you to severe and sudden tire damage caused by external factors. Another factor which the Flat Tire Monitor does not recognize is the balanced and very gradual pressure
loss that takes place in all tires over an extended period of time."


Seems reasonable as you need to concentrate on controlling the car in a tire blow out situation and not be distracted by a ding and light on the dash. The blow out should be enough of an indicator that something went Top Gear/Grand Tour wrong.

 

A week ago as I was driving into town for gas I was getting a little frisky with the go pedal on our two lane road when the low tire light came on. I didn't feel anything unusual and when I looked the tires over at the gas station they all looked OK, so I ignored the light and a few miles later it went out. When I checked pressures at home they were pretty equal although a few pounds below the 35 PSI I usually run

Perhaps I spun a tire to set it off? It has 215/45R17 tires all around.

EDIT: I just looked up the Fuzion UHP Sport A/S tires that came on my Mini, and apparently they are notoriously slippery, even in the dry, (and some say absolutely dangerous in the wet). Good thing I checked so I know to be careful in rain, although I drove it 120 miles home in rain with no problems when I bought it , but it was totally new to me then and at night so I wasn't pushing it.