Tire Pressure for Upsized tires?

[Jeffd]

I had the FX4 225/65/17 Perelli scorpion tires on my XLT and Ford has recommended the tire pressure listed as 35psi. I just swapped them out for some BFG KO2 245/65/17. Do I keep the same recommendation 35 psi even though the tire is larger? If not what should I run? I’m new to breaking the rules.

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[JKinPA]

36 to 38 is where mine are at
245 Falken Wildpeak Trails

 

[jadatis]

This " pigheaded Dutch selfdeclared tyrepressure-specialist " registerd to this forum,to give reaction here.

There are 2 ways.

First see what loadcapacity stands for 35psi , for the old tires. I can help you with that. Then calculate what pressure the new tires need to cover that same loadcapacity.

Problem then is that you dont know for wich speed the advice is given.
Also you dont know what calculation was used. And the 35 psi could be yust the referencepressure, and not calculated for load and speed.

For this you would expect a bit lower pressure for the 245 against the 225.

Better way is to let me calculate it for the GAWR,S, better weighed axle- loads in the loading you use it, and give the max speed you use, and wont go over for even a minute

If the carmaker calculates the advicepressure its nowadays mostly for GAWR ( gross axle weight rating) and maximum technical carspeed.

So to calculate it I need from tires
1. Maxload or loadindex
2. Kind of tire to determine the referencepressure
3. Not superimportant but the speedcode of tire

This then from old and new tires.

2. P- Tires Standard load AT 35 or 36 psi
( is reference-pressure)
P-tires XL / extraload/ reinforced AT 41 or 42psi
LT tire C-load AT 50 or 55 psi.
LT tire D- load AT 65psi.

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