I've heard that you can trick the computer with a sealed tube pumped up with a sensor in it when you put it in your trunk (I forgot where the thread for that is). So does that mean I can put a sensor in one wheel and it will ok? I want to run different wheels for summer/winter. And I would rather not carry anything in the car if possible.

 

Would expect it would want to see four, that is what would be sealed inside a pressure tube.

 

ok - thought that you only sealed one sensor. Guess it needs to read 4. Thanks

 

Have you ever seen how big a tire tube is under 35psi? It's about the size of the area of your entire back seat. The computer needs to see signals from all 4 sensors to keep the light off.

 

does the computer need to see some certain minimum pressure? or does it just look for an equal value among all sensors? The sensors could be in any pressurized container I guess but probably wouldn't pick up a signal through a metal container or would it?

 

I do not think using a 'pressure vessel' is a smart idea at all, but if you do,
just use a short length of PVC Schedule 40, two caps and a Schrader Valve.

 

Yeah your'e probably right there! I took a high pressure safety class years ago at a National Lab where we learned that area times pressure=force. They gave an example of a mechanic who unbolted a lid from a large tank where the pressure gauge was reading zero, turns out the gauge was off by 2 psi and the mechanic was killed. the lid was several hundred square inches multiplied by 2 psi equals a shitload of force!

 

It looks at each sensor individually, so if a tire picked up a nail, when the pressure gets low enough the light would come on. On the Mini's I am not sure where the antenna is for the computer, but I believe the sensors need rotation to charge them.

 

So I guess you just don't want to spring for a second set of TPMS's in your second set of wheels? I believe the rotation of the wheels activates the sensors, so if you have a sensor just sitting still in your trunk, it won't transmit and the computer won't see it.

I'm just getting a second set of TPMS's in my new wheels. They're about $200 for all 4 sensors and the required valve stems. You'll have to reset the system when you swap wheels, but it only takes a couple minutes. The procedures are in the manual.

Good luck,
Chris

 

Shameless Plug....

Tire Rack has supplied an article on TPMS found on all 2007.5 - current MINI's for the NAM Alliance Magazine. Expect it to be published on or about Oct 24. Do NOT have to be a NAM Alliance Member to download and enjoy.

TPMS light is triggered to come on if the pressure drops to below ~27-28 PSI. It's quite possible for a tire aired up during a warm afternoon to drop enough pressure on a cold night.

 

guess I'll haev to get another set of sensors. Unless the 10/24/08 article say's different