Why did Ford drop PSI from 44 to 38 for Gen 2?

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vegascarnut

vegascarnut

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I believe this is D rated load PER TIRE at these pressures, but it gives you an idea:

LT315/70R17 load capacities

50 psi=3195lbs
45 psi=2915lbs
40 psi=2685lbs
35 psi=2535lbs

In other words, as long as you aren't beyond those loads per tire then your tire will not be out of shape. According to this, at 35psi you could support a 10,000lb truck.
 

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I'm going to try it. Tires really ride great overall, but always trying to make things just a little better! Haha. I'll take it down to 38 and see how that feels first. I run load range E tires because I tow a boat quite a bit. 44 PSI seems like overkill for unloaded daily driving though. Thanks

I’m running load range "E" BFG KM3’s at f34r30 for unloaded daily driving. The sidewall squat is about right at those pressures, and they should wear more evenly than my last set.

Running the backs at 38 on the factory k02’s wore the middles down too quickly.
 
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vegascarnut

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I’m running load range "E" BFG KM3’s at f34r30 for unloaded daily driving. The sidewall squat is about right at those pressures, and they should wear more evenly than my last set.

Running the backs at 38 on the factory k02’s wore the middles down too quickly.

I’ll probably try that out too. I ran my KO2s at factory 44, and they wore fine for 45k miles, still had tread. I little thinner in the middle but not bad. They were just too rough at that pressure.
 
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abearsfan

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I use the chalk method for checking tire pressure/even tread to ground contact. helpful if you run different size and or brand of tires than OEM.
 
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That doesn't really work because the tires will change shape when there rotating.

You'll just have to readjust pressure after rotating. Chalking is more of a pressure relationship right? Once you know what's best for front/rear, you just reset the pressures where they were on front/rear after they are rotated, and you'll be good to go—unless I'm missing something, that's the way chalking works for me!
 
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I've been running these 35x12.5R17 KM3s at 38F/36R for about a week. They ride really nice at that pressure. They chalk out fine too. They also chalk out fine at higher pressure (44/40). What I've noticed is that at the lower pressure the ride is substantially better. The negatives of the lower pressure are that low speed turns put more strain on the steering pump, and on the highway they are just a little bit louder. I'll have to decide what's important to me, but since I'm not on the freeway much, the lower pressure might be the best trade-off.
 

EricM

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You'll just have to readjust pressure after rotating.

He's saying rotating- ie driving.

I've ran mine anywhere from 32 to 44. 36 to 38 most of the time. No TPMS sensors and I disabled the whole system in Forscan. I got eyes and pressure gauges.
 
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vegascarnut

vegascarnut

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I've ran mine anywhere from 32 to 44. 36 to 38 most of the time. No TPMS sensors and I disabled the whole system in Forscan. I got eyes and pressure gauges.

I used my x4 programmer to lower the pressures on the TPMS to 35. What size/load range are your tires?
 
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