QuestionI have a extened cab 02 tacoma sr5 and went from 265/70r16 4 ply to a lt245/75r16 10 ply tire. I have herd that 80 psi can cause rim failure and was wondering how much psi to put in emty and also with weight. they have 40 psi now. I sometimes have weight in the bed or haul a small trailer.
AnswerDru,
I am not a fan of replacing P metrics with LT metrics. While I have heard lots of folks extol the virtues and their success stories - which I don't discount - I approach this subject from purely an academic position.
LT tires take more pressure - about 15 psi - to carry the same load as a P metric. Why? The only thing I can figure out is that LT metrics have high unit loading - a large amount of load carrying capacity compared to the amount of space they occupy - for the higher load ranges (and therefore, higher pressures). The rubber used in LT tires is correspondingly strong - and what comes along with that is a susceptibility to cracking when flexed.
So unlike P metric tires, which are designed to flex, LT metrics are not designed to do so. While this is mostly thought about in the sidewall, because of the difference in the way these things are designed and tested, this carries over into tread and belt durability as well - meaning tires falling apart.
I don't have any good reliable data to back this up - as this type of trade is rare enough to be thoroughly obscured by return data.
But to answer your question, according to Tire Guides a 2002 Toyota Tacoma originally came with a variety of different tire sizes, but the version that came with p265/70R16 were inflated to 26 psi front and rear. Please check you vehicle placard to make sure this is right because what I am about to write depends on this.
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.
So if the placard matches what I wrote, in order to carry the same load, an LT245/75R16 needs to use 42 psi.
