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TPMS - Need an Expert

1K views 1 reply 2 participants last post by  Justice619 
#1 · (Edited)
2015 Rav4 XLE. Need to know for sure how TPMS works. Contacted Toyota and was told it triggers light for under inflation only. Some other persons, tire dealer sites, Toyota dealer employees, etc have stated that TPMS will trigger light for over inflation also. I am aware of the older TPMS (my previous vehicle) that triggered light based on the ABS sensing differences in tire rotation based on change in tire diameters with different pressures. But I am asking about the new (e.g. 2015) TPMS that I believe measures the actual pressure in the tire, unrelated to the ABS system. I understand that if 3 tires had 33 psi (the recommended psi) and the 4th tire had 50psi, who knows if the light would go on (although I think it would not). I need to know if the light would be triggered if all 4 tires had about 44 psi in them. I am quite sure that the answer is no, as Toyota told me, and that only under inflation (perhaps greater than 25% or so) will trigger the light. Does anyone know for sure? Thank you for your help. Maybe I need to call TPMSdirect.com. Different Toyota sources had different answers.
 
#2 ·
I've worked with a lot or vehicles in my shop. Mostly installing new tires. We had a Yaris in our shop that had the flashing TPMS light. Normally, that would be a bad sensor. But, the problem was the tire was over inflated to 80 psi. The customer kept adding air to the tire because it "looked low". Just goes to show you don't need to take a common sense test to get a driver's licence. Brought the air pressure down to 35psi and the light turn off.

There is a point to where over inflating the tire will make the light come on. But, 44psi isn't high enough to cause problems. More like 65psi or more. The best rule of thumb for setting the right air pressure is how the tread on the tires are wearing. If wearing on both sides of the tire, not enough psi. If wearing in the middle of the tire, too much psi. The goal is to have even tread contact to the road. In reality, there really isn't one set psi level for all tires. All types and brands of tires all wear differently because all tire aren't made the same. Door placard is more of a minimal psi recommendation not required psi.

 
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