There's been a lot of talk about TPMS (Tire Pressure Monitoring Systems) since they became standard equipment on some very mainstream cars. Vehicles equipped with TPMS continually monitor the pressure in each tire individually. If one of the tires experiences a drop in pressure, the computer alerts the driver. The Toyota Prius is probably the least expensive vehicle to sport this new technology, but to get the kind of fuel economy it shoots for the tires need to be at full inflation.

Unfortunately, along with this exciting new technology (soon to be mandated by the NHTSA) comes a bunch of new misinformation. One of these pieces of folklore made it into the ears of this reader. Jim writes:

I have a 2006 Prius. I traded my Lexus IS300 for it and I am super satisfied. I get 45 - 47 mpg, it’s got a comfortable ride, has plenty of pep, although not a race car and has great inside space for passengers and stuff! Got IRS hybrid tax credit also and no CT sales tax.One detail they don’t talk about however, is the difficulty in changing from all season tires to winter tires each year (in snowy New England) It’s very expensive to do this because each tire has a pressure sensor in it that must be in each wheel before putting the tire on. It costs big bucks when putting 4 snows on!

Lucky for him, this piece of information is wrong. The TPMS sensors are attached to the wheel just underneath the valve stem. When the tire is removed, the sensor and stem stay behind. This means you can run any tire you want as long as the sensor isn't damaged in the changeover. If you drive a car or truck with TPMS, it's a good idea to tell the tire tech to be very careful with your wheels, and definitely don't replace the valve stems! Unfortunately, if you want to own separate wheels for winter and summer, you'll have to purchase another set of sensors, not cheap.

photo of TPMS sensor courtesy Toyota.