Tire Pressure Sensor in Spare?

[stream]

Originally Posted by Boo

That would be ideal. Which car has that now?

Porsche does, and I suspect some/all of the luxury brands do.

[bluetwo]

Originally Posted by jay_man2

I used to check tire pressures every Saturday morning, along with the fluid levels and battery indicator (the green or blue eye on a 12v battery). With the advent of TPMS, I'd completely fallen out of that very useful habit, but I'm trying to work it back into my weekend routine.

Which is totally understandable. ...and I think I've seen where it's general consensus that the TPMS systems wont give you a very exact pressure. They'll let you know if you drop below the threshold, likely to be 25 or below, but for now they can't be used to monitor the tire pressure in an exact way like some of us might like to do.

[jay_man2]

Originally Posted by stream

You could attach an extension hose to the valve stem:
Chek-a-spare, Check-a-spare, tire gauge guard

They make excellent quality pressure gauges--here's the one I use:
Dial Tire gauges

Thanks! I was going to look for something like this.

[RodJo]

Originally Posted by stream

Porsche does, and I suspect some/all of the luxury brands do.

My wife's Caddy also displays psi for each tire, and it seems pretty accurate. I assume the Prius sensors are not very accurate, so that even if all tires were at the same pressure, each sensor would report slightly different numbers. If those readings were displayed, it would drive us nuts and we would complain.

It seems that for a few bucks (okay a few hundred bucks) the sensors could be more useful. What does Lexus do?

[Boo]

Originally Posted by bluetwo

Which is totally understandable. ...and I think I've seen where it's general consensus that the TPMS systems wont give you a very exact pressure. They'll let you know if you drop below the threshold, likely to be 25 or below, but for now they can't be used to monitor the tire pressure in an exact way like some of us might like to do.

If the Gen III TPMS is like the Gen II's, then the threshold is 25% below the psi that the TPMS is set for (note that you can trick or monkey around with the TPMS so that the threshold is effectively lower than that 25%).

So if the TPMS is set for 40 psi, then if any of the 4 tires drops to 30 psi, then the TPMS warning light icon should go on.

[rachaelseven]

Originally Posted by stream

Some TPMS systems show the actual tire pressure for each tire.

The Prius system does record the pressure for each tire and set an individual threshold for each one. You can see each pressure listed separately and each associated threshold when you look at the Techstream device. The car doesn't display all 4, which could be annoying or helpful, depending on your point of view; but it does process each one individually and set separate threshold values for each one. From what I can see, the threshold is less than 20% - my 48.2psi fronts have thresholds of 40.6psi and my 46.0psi rears have thresholds of 38.4psi... looks more like an 8psi spread to me. The system also seems to track internally down to the tenth of a psi, as you can see from the readings above. And interestingly, it also tracks temperature as well as pressure, down to the nearest degree F.

[stream]

Originally Posted by rachaelseven

The Prius system does record the pressure for each tire and set an individual threshold for each one. You can see each pressure listed separately and each associated threshold when you look at the Techstream device. The car doesn't display all 4, which could be annoying or helpful, depending on your point of view; but it does process each one individually and set separate threshold values for each one. From what I can see, the threshold is less than 20% - my 48.2psi fronts have thresholds of 40.6psi and my 46.0psi rears have thresholds of 38.4psi... looks more like an 8psi spread to me. The system also seems to track internally down to the tenth of a psi, as you can see from the readings above. And interestingly, it also tracks temperature as well as pressure, down to the nearest degree F.

Which isn't very useful...unless you drove around with a Techstream device in your car...

[rachaelseven]

Originally Posted by stream

Which isn't very useful...unless you drove around with a Techstream device in your car...

Yup. About how I see it. Darn shame Toyota didn't give us access to more of the information/features that seem to be already available in the TPMS system though.

[Boo]

Originally Posted by rachaelseven

Yup. About how I see it. Darn shame Toyota didn't give us access to more of the information/features that seem to be already available in the TPMS system though.

Maybe Gen IV will show this useful info.

If the past is any indication, Toyota doesn't seem to favor mid-generational changes. E.g., it took Toyota a whole generation to move the driver seat's furthest rearward travel point back 2.5 inches. IMO, they could have made this change in 2005 and it would have cost no more than a few pennies or dollars per car.

[Glider]

Originally Posted by rachaelseven

I'm honest enough with myself to admit that I will never check the pressure in the spare. I mean seriously... it's all I can do to check the pressure in the 4 on the car...

If I'm honest, I'll admit I'm lucky to check anything unless I think about it. I guess I check tire pressure once a month, if I'm lucky. I tried to regularly do a walk-around each morning before getting into my car (walk around the car and look at the tires) - that lasted about a week. Anyway, a tire has to be way down in pressure before you can see it.

This brings up my new definition of an optimist. It's the guy or gal who wrote the Prius manual and said: "Make sure to check the inflation pressure as part of your daily vehicle checks (p439)"

Anybody out there checking their tire pressure daily? Weekly? Be honest