Quote:
Originally Posted by CalandLinda
It's a question often discussed here. For me, the answer is always the same. The correct inflation pressures for your OE tires is what has been recommended by the vehicle manufacturer. The vehicle manufacturer's recommended cold inflation pressures are depicted on the vehicle certification label, tire and load label and in the vehicle owner's manual. Unless; there is optional/supplemental recommendations from the vehicle manufacturer.
That statement or one like it will be found in every reference you ask for when hunting for your vehicle's correct inflation pressures.
Optional inflation pressures between vehicle manufacturer cold recommendations and tire sidewall maximums is at the discretion of the consumer.
The USTMA supports the vehicle manufacturer's recommendations by stating that your tire inflations should NEVER be lower than what has been recommended by the vehicle manufacturer.
NOTE: The tire manufacturer will list, on the tire sidewall, the maximum permissible inflation pressure needed for that tire to provide its maximum load capacity. It's not a recommendation. It's intended to be informational.
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While completely correct and I agree with the recommendations, I'll provide alternative data for consideration.
First note that the manufacturers recommended MAX pressure is to support the manufacturers rated MAX load. IOW, you cannot safely achieve rated GVWR with less than the manufacturers recommended tire pressure.
However, heavy duty pickup trucks are also extremely variable in their weights compared to other classes of vehicle on the road. Commercial work trucks run loaded almost all the time, so they run recommended max pressure every day, no question. On the opposite side, cars often have only a few hundred pounds of difference between empty and loaded, so MAX pressure also works good; it supports the weight and conveys a smooth ride whether empty or loaded.
Compare the above to the HD pickup, especially the rear axle. For a 3500 class vehicle, the rear axle weight could vary by as much as 4000lbs or more during typical driving conditions -empty vs loaded. What tire pressure would be adequate for empty weights vs loaded weights? We don't have to guess, those ratings are published.
The OP didn't provide tire size, but PSFORD99 provided his tire size at LT275/70R18.
https://tirepressure.com/lt275-70r18-tire-pressure
Based on the tire pressure chart, and given that PSFORD99s 2014 RAM 3500 has a 6000lb front axle and a 7000lb rear axle, you can see why the manufacturer has recommended 65psi front and 80psi rear.
To determine what might be a safe empty tire pressure, lookup the information for the truck, in this case,
http://www.rambodybuilder.com/2014/d...ammlup3500.pdf
Assuming the most popular RAM, a Laramie cummins crew cab short box 4x4, the empty axle weights are; ~4800lbs front axle and ~3000lbs rear.
Back to the tire charts and you could see that empty the rear axle is so light that even 35psi would technically work; and the front axle, empty, could go as low as 40psi. But at those pressures most LT tires would feel very squirmy and have poor wear.
What's the point of the above? There is a bit of art meets science here. If you are loaded, use the max tire pressure recommended by the manufacturer on the door sticker (not the max on the sidewall).
But, if driving empty, you can easily lower tire pressure by a considerable amount and still safely carry the load. The limiting factors then become how does the tire feel and how does it wear?
Most LT tires will feel ok at 55psi, and some feel ok below that.
Then, if you want to check on wear, air the tires to where it feels good empty, and do a chalk test. Put a thick chalk line across the tire, drive ahead on dry pavement and see where the chalk makes contact. If even across the tire, then the pressure will be fine.
Again, I completely understand that the "correct" answer is to follow the stated manufacturers recommendations. But running tires at 80psi to support a 7000lb axle load then only loading them at 3000lbs, will not provide a smooth ride. So if you want a nicer ride empty, the above provides an example of research to support doing that safely.
Just make sure to air back up when loading up.
hth
Brad