QuestionBarry:
I have a 2007 Toyota FJ Cruiser with ProComp Xtreme A/T
LT305/65R17 tires. I do mainly highway driving. What's the best tire pressure for a comfortable ride and fuel efficiency?
AnswerSam,
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.
BTW, it doesn't matter who makes the tire or what pressure is listed on the tire's sidewall, if the tire size is the same as the placard, then the pressure listed on placard is also appropriate.
One word of caution: Some trucks use tires with the letters "LT" in front of the tire size - and some trucks use tires with the letter "P" in front of the tire size - and some trucks use tires with the letter "C" after the tire size. You should not use "P"'s in place of "LT"'s and vice versa.
You should be sure the pressure on the sidewall equals or exceeds that pressure on the placard. If you do this the issue about the letter "C" in the sidewall will take care of itself (which is not true with "LT"'s vs "P"'s.)
If you are using a tire size that is different than what is listed on the placard, then the pressure has to be recalculated. The calculation is not difficult, but it requires tire load tables which are not allowed to be published in the Internet because of copywrite laws. However, I have a copy and would be glad to do the calculation, but the starting point is the vehicle placard: Tire size and inflation pressure. I will also need to know the new tire size.
According to Tire Guides. your vehicle placard should say the original tire size was P265/70R17 mounted on a 7 1/2" rim inflated to 32 psi. Please check this because what I am about to write is dependent on this being correct.
In order to carry the same load an LT305/65R17 would need 37 psi.
BTW, I hope you purchased rims as the stock rim is only 7 1/2" wide and an LT305/65R17 requires an 8 1/2" to 11" rim.
