QuestionQUESTION: My vehicle is a 2009 Dodge 1500 TRX 4x4. Factory tires are 275/70R17. I recently put on Toyo 285/75R17 (with a slight lift). The installers put the tire pressure at 60psi. How do I determine the correct pressure or is this a personal preference issue? Thanks.
ANSWER: Kenneth,
On every vehicle sold in the US, there is a sticker - commonly called the placard - that will list the original tire size and the proper pressure for that size. The placard is usually located on a doorpost or in the glove box, but sometimes it is located in the trunk or on the fuel filler door.
Since you are not using the original tire size, the placard pressure is not appropriate,but it is the starting point for figuring out what you ought to be using.
So if you will post back with the pressure (we already know the original tire size and the new size), then I can do the calculation.
---------- FOLLOW-UP ----------
QUESTION: The posted pressure is 37 psi for the original Goodyear Wrangler AT. The reason for the question is because the Toyo tire is an E rated 10 ply tire. Thank you for the prompt replies.
AnswerKenneth,
Normally I would go through a calculation where I would calculate the load carrying capacity of the original tires (the placard size at the placard inflation pressure) and match that with the new tire size.
However, there is a lower limit that represents - in my view - an unacceptable risk of the tire being unseated during emergency maneuvers. For passenger cars, it is 26 psi, and for Light Trucks it is 35 psi.
It did not take me very long to realize that I was looking at a situation where the calculation was going to give me a number lower than 35 psi.
So I do not feel comfortable recommending anything lower than 35 psi.
Please note that the fact that the LT286/75R17 is a Load Range E doesn't enter into the equation- except to say it represents an UPPER limit.
