More psi info
I have the same question, Kramer. I just bought a set of BFG All-Terrain T/A KO's. They are LT265/70R16/D, the same size as my originals, only LT's instead of P's. The manager at Discount Tire told me to keep them at 45 psi because they were "rated 65 psi max" and would run too hot at lower psi. The tech who checked my allignment after the purchase was from another garage, and he agreed with the store manager. The tech said to keep at least 40 psi in them or else they might separate from the rim if I turned sharply at highway speeds! He didn't even mention the heat issue.
However, several 4x4er's I have talked to since the purchase, including a service writer at the local T-dealership, say I will prematurely wear out the center of the tire at those pressures. I performed the "chalk test" to test the warning about uneven wear. I drew a thick white chalk line across my left front tire and drove my Runner straight ahead about 40 yards at 2-3 mph and then checked the line. The center was almost worn off while the lugs on the outside edges were barely touched. I dropped the pressure all around to 36 psi and repeated the test and discovered nearly uniform wearing. The 36 psi was with warm tires. When I checked the test pressure the next morning with cold tires, they were 33 psi. So indeed, there is evidence to suggest 40-45 psi could cause your tires to wear unevenly.
What I don't know about is the separation of tire and rim during high speed cornering nor the heat issue at highway speeds. I have not been able to find anyone in person or on the net who has heard of a problem when the pressure is 28-35 psi, no matter what tire, except maybe the old Firestones in summertime Texas. Even guys with large mudders on tiny lifted older Tacos run at 35 psi or less on the highway and drive as fast as their little 4-bangers will scoot with big boots. I called BFG customer service and they won't answer any questions because their chart doesn't show my size tire being recommended for a 4Runner. Legalities, I assume.
Selecting the correct highway pressure for any tire seems to be a matter of adjusting to the load, and you know you have the right psi for the load when the tire wears nearly uniformly on its available surface (the chalk test). I think I'm gonna run 32 cold psi on the highway with my KO's, which I really like by-the-way. (They crawled through some fairly deep north slope snow with a fresh covering southwest of Pikes Peak last Saturday morning without the slightest slip nor a bit of tire damage--there were plenty of rock and ledge surprises under the snow.)
On the other hand, if the Discount Tire manager is correct about 45 psi for highway safety on 65 psi max. LT tires, someone needs to speak up ASAP and present the evidence.
2000 SR5 5spd V6 with optional 16" wheels. No mods yet.
