Tire Pressure Sensor in Spare?

The manual (p343) says that the compact spare tire does not come with a pressure warning valve and transmitter. I think that's the spare tire I got with my car - not sure about yours. Also, I remember the service rep saying it didn't have one.

I don't remember getting any computer printout when I bought the car. Was this after you had it serviced?

- g

 

Sorry, its p434.

 

That was good thinking Rachael. TPMS sensors are actually far more of a PITA than they are good, just speaking in terms of percentages. The number of people they've inconvienced has got to be far greater than the people who have actually needed a little light to come on and say they dummy you have a low tire.....

They are just as much a pain to people who want to have an extra set of snow tires as they are to people who put performance rims and tires or bling/bling wheels on their G ride. Usually, from what I've read about most models, it only takes a few minutes of riding around after the spare is removed and stowed again for the regular tire pressure monitering system wheel to communicate with the ECU and turn that pesky dummy light out again.

 

Sorry, forgot to mention that this is a very good point. I rarely check my spare (dumb me) and it wasn't too long ago, on another car, that I asked them to use the spare as part of the tire rotation and had them inform me it had something like 10 PSI in it. A flat spare isn't much good is it??

- g

 

The bad thing about the spare is that the the way it's stowed the valve stem is face down, so it's a major PITA to pull the cargo box out, pull the spare out, then check the pressure.

 

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.

 

If you flip the car upside down it's much easier to get to the valve stem and check the pressure.

Tom

 

I check my tires monthly--give it a try--weekly is probably a bit overkill, and the monthly schedule is more likely to be performed. The TPMS threshold is so high (8 PSI as I recall) that I wouldn't want to rely on it, short of when you get a flat tire.

 

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

 

The spare holds air pretty well, I usually check mine once a year and put 65 or 70 lbs in it. If I need to use it I'll check it and let a little out if needed.

My cynical side says the reason the TPMS sensor ID can't be changed by the car owner or even the tire shop is because dealers have pressured manufacturers to have a lot of simple stuff on the car that only they have the software to change. That way the dealers can charge an hours expensive labor to shut off the annoying backup beeper or change the sensors, which should take no more than 5 min.

Unfortunately it works because to many customers think "Toyota knows best" or "if the dealer said so it must be true".

OK, now I'll climb down off my soap box.

 

AFAIK, a tire pressure sensor in the donut spare wouldn't work because the 4 regular tires have a recommended psi of around 35 psi, while the donut spare has a recommended psi of around 60 psi(?).

So if the Tire Pressure Monitoring System were set for the 4 regular tires' 35 psi, and the donut spare had a sensor in it, the donut spare would have to be at around half of its recommended 60 psi in order to trigger the TPMS warning light.

Although this would be somewhat useful, I'd rather save the $100+ cost of a tire pressure sensor in the donut spare.

 

There are some vehicles that allow you to register two sets of TPMS id's, but AFAIK these are luxury import SUV's. The principle behind the luxury import SUV allowing two sets of TPMS keys is that one set can be used for the normal tires/wheels, the second set for either off-road or studded winter tires on separate wheels

 

Kind of odd too, when you consider that the additional cost in electronics is next to nothing. The logic and memory requirements are trivial.

Tom

 

Probably in the future, TPMS will have at least 4 settings -- one for each tire -- and show exactly which tire is underinflated.

 

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

 

That would be ideal. Which car has that now?