QuestionQUESTION: I recently replaced my original OEM tires (BF Goodrich Rugged Trail 285/70/17 max load 2833 @ 35psi), with (Nitto Terra Grappler 295/70/17 max load 3195 @65 psi). This is on a 2005 Nissan Titan with 17x7.5" rim.
The tires seemed to be not making contact with the road on the outer edges approx.1" or so, dropped pressure to 55 psi and seemed to remedy this.
Would it be ok to run this psi unloaded?
ANSWER: James,
On every vehicle sold in the US, there is a sticker – commonly called the tire placard - that lists 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.
Please check that placard because what I am going to post next depends on this being correct.
Tire Guides says a 2005 Nissan Titan originally came with P285/70R17's inflated to 35 psi on 17X7.5" rims. This equates to a load carrying capacity of 2575# (after derating the tire 10% because it is used in a light truck application)
You didn't say so, but the new tires have an LT in front of the tire size and that's important, because these are rated in a different way and have different load standards. (plus it looks like you made a typing error - the tire size should be LT285/70R17!)
An LT285/70R17 has a load carrying capacity of 2755# at 50 psi and 2890# at 55 psi, with a maximum of 3195 at 65 psi.
So extrapolating, the tire needs 51 psi to carry the same load. This pressure should be OK for up to the payload of the vehicle.
---------- FOLLOW-UP ----------
QUESTION: Yes it is a LT tire, and the size is 295/70/17.
AnswerJames,
It took me awhile, but I did find the tire size. It's a 123R Service Description. But this doesn't line up with the load carrying capacity you said is on the sidewall of the tire - a 123 ought to say something around 3415# maximum load.
But I know a few tricks - and assuming that the Load Index is correct and either you've quoted the sidewall incorrectly, or it is stamped incorrectly - then the pressure I calculated would drop to 46 psi.
