let me tell ya what "mandatory" TPMS is doin for all the 4 wheels now that USGvt has helped out. all cars /trks must have em by 09.heres the rub. kiss the term "free tire rotation " good bye!! im a goodyear dealer. in order to rotate many tires now you have to have equipment to reprogram the system so it knows that the left frt tire is now the left rear tire. naturally they're not using a uniform sytem so there are many tools to buy to perform this, more time involved, you're actually supposed to "rebuild" the TPMS stem assembly anytime you remove a tire from the wheel (more time and $$$$$$$) and some manufactures systems actually require you to return to the dealer to have the lite turned off. TPMS good? maybe. costly? absolutley