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Discussion Starter · #1 ·
I've read a fair amount of discussion on the forum regarding both running the tires at a higher PSI for better mileage and also upgrading to better tires. In my manual, it mentions that the tires have to be equipped with tire pressure warning valves and transmitters for the low tire pressure alarm to work properly and also if the PSI is more than 7.3 PSI higher than standard, the alarm will not work correctly. Were/what are these valves and transmitters and how would they be transferred to new tires? Also, has the higher PSI created any false alarms? Toyota is even recommending that flat tires have to be repaired by Toyota or run the risk of the valve or transmitter not working properly. One last thing, the manual also says that the ID code has to be registered?
 

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Don't know about the Prius as mine hasn't arrived yet, but the BMW MINI uses the vehicle stability control sensors to determine if a tire is going flat. The difference in the tire's rotational speed compared to the other tires indicates a loss of air. I wouldn't be surprised if the Prius works the same way with it's stability control. Actually monitoring the air pressure within each tire would be cumbersome.
 

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There was a thread on this forum about this topic. However, I have not been able to find it using the search function. Since the low pressure warning system only comes on the 2006 (I think), there probably are not too many members familiar enough to comment. I do recall that tires can be replaced by any reputable tire company and do not have to be changed by Toyota.

Just found the thread: http://www.priusonline.com/viewtopic.ph ... 2&highligh
 

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Discussion Starter · #5 ·
I was at the Toyota dealership today and asked the service person to explain the valve/transmitter. I was told that there are two sensors, one in the valve itself and the other on the back of the rim. If someone else is changing/repairing a flat, they usually pop out the valve. Popping it would damage the sensor. Also, if other tires are used, they need to be registered (didn't explain how). If you have to use the knockoff spare, the sensor will alarm thinking the pressure is low.
 

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I have an 06. I replaced the stock wheels with 17" rims and tires. The sensor is attached to the valve stem. You must remove the valve stem from the stock tires and transfer them to your new wheels. Then you have to reset the tire pressure sensor in the car. The button is under the steering wheel (see manual). I did'nt do this at first and the sensor light went off. After transfering sensors and reset works great.
 

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Discussion Starter · #8 ·
Grovey, were there no no sensors on the back side of the wheel? Also, do you have navigation? It would seem that the system would have to know the new wheel diameter for the consumption reading to be accurate as well as the navigation.
 

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I can answer that one. It compares the distance driven based on GPS versus distance driven via wheel rotation, and adjusts ded reconing distance to fit the GPS distance. GPS is very accurate over long distances, but ded reconing is more accurate for short distances.

Won't help though for the speedometer/odometer.
 

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Gman, there are no sensors on the back of the wheel. The 17" rims and tires I installed have the same diameter of the stock 15" wheels. The difference in rim size is made up with the low profile tire on the my 17's. Also would like to say, I think the car drives much better with the 17's. Very stable on the highway, which it wasn't at first. Here's a photo of my car.
 

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