What psi should I run ??

[MTMan]

What I've used to help get a reference point is using the Falken Tire Load Pressure chart and cross reference the factory tire specs on it to the new tire. Sometimes this can be very surprising especially coming from a P size tire to LT.

I'm into the off-road world and another thing I ran across as an example is that a 1998-2002 Land Cruiser factory tire pressure is 29F/32R. The BFG A/T replacement tire on their website in the same LT size says:

Front & Rear
275/70R16 119S RWL

Requires pressure increase to 41 PSI

These tires are different than specified on the tire vehicle placard. This size requires an increase in inflation pressure to 41 PSI for proper and safe application. The TPMS system will likely require re-calibration with this inflation pressure adjustment, consult your vehicle manufacturer’s representative for TPMS assistance/instruction. For tire assistance, consult your dealer for more details.

Interestingly, 2 years ago this said 41F/44R

Point being, good to do research beginning with a load pressure chart for safety to not under inflate risking blowouts due to high heat.

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[Je1279]

For those who may not know, once you determine the necessary psi for your LT tires, you can alter the TPMS values within the BCM via forscan to reflect the new values.

 

[amschind]

Yeah, thanks man. I heard the KO2’s were not that great in the rain but supposedly the new version ko3 are better in snow rain, and just all around. I guess we’ll see this winter. lol I’ll post some before and after pictures once they get installed on Thursday

I have never had an issue in the rain with them, and I think I have run every version of BFG ATs made (or at least since 2000). A premium touring tire will probably get better traction, but even towing heavy stuff with T/A KO2s I have never been concerned about stopping. I will also note that I have nearly 50k miles on mine with notable tread left....I think they will hit 60k miles (27k=>75k now, hoping to hit 85k). KM3s are awesome off road tires, but all of those "as good as a touring tire from the 1990s except that it's an AT" compromises that make the T/A KO2 so great vanish with MTs.

The KO2 and probably also KO3 are noisy tires, which is the one real knock on them.

 

[jcru1017]

Wow, you guys run high pressure. I'm running 37/12.50/17 RTs. I'm about 32psi cold.

 

[jadatis]

Mind that LT tires need higher pressure for the same load then P-tire in same size.
Can go upto 15 psi more, going from Standard load P-tire ( AT 36 psi) to LT E-load ( AT 80 psi)

You could calculate the lbs/psi and see that its less for the AT 80 psi LT, then the AT 36 psi.

But nowadays often yust referencepressure is given as recomended, and if calculated for GAWR and max technical carspeed, it might come to low in the 20's psi.
Then 15 psi higher is 35 psi, so then still 35 or 36 psi is enaugh for the LT.
So you have to determine it from basic data.

Now dont follow this in the blind, first determine axleloads , add a reserve ,and calculate. Lineair calc can do, gives slightly to hig pressure, so never unsafe for the tire.

Reason is that because of stiffer tire, by constuction to hold more pressure in , and also yust by the higher pressure, a snowball effect. The overgoing curve from unloaded radius to flat on the ground, is larger, wich gives lesser surfacelength, so surface at the same deflection.

Here, a paint image ,I made for it years ago.

And topicstarter, once the tires are mounted, search on sidewall if you see AT 80 psi or AT 65 psi on tire.
That is leading. Mostly E-load/LRE is AT 80 psi, but this could be that larger size that gives AT 65 psi. Then I have to make a new list.

 

[pittman]

Wow, you guys run high pressure. I'm running 37/12.50/17 RTs. I'm about 32psi cold.

I'm with you. Doesn't make any sense to run larger tires with stiffer sidewalls at a higher pressure. Tires have to conform to the road to generate a proper contact patch, absorb bumps and wear properly. The only indication for increased pressure is an increased load.

I see so many folks with KO2s with poor wear in the middle of the tire. This is due to over-inflation. I am certain that these are the same pleople complaining about poor wet traction.

I ran 28psi cold in my last 2 sets of KO2s. Never had traction concerns. They wore evenly and each set last beyond 100k kms each. They also didn't explode.

 

[HammaMan]

I'm with you. Doesn't make any sense to run larger tires with stiffer sidewalls at a higher pressure. Tires have to conform to the road to generate a proper contact patch, absorb bumps and wear properly. The only indication for increased pressure is an increased load.

I see so many folks with KO2s with poor wear in the middle of the tire. This is due to over-inflation. I am certain that these are the same pleople complaining about poor wet traction.

I ran 28psi cold in my last 2 sets of KO2s. Never had traction concerns. They wore evenly and each set last beyond 100k kms each. They also didn't explode.

Ford's own PSI ratings for E LT tire ratings would be listed on PB for instance as....
145" WB 43F, 45R (3900, 4150)
157" WB 45F, 45R (4050, 4150)

Here's their C LT stickers for only 7,000 GVWR w/ 3600, 3800
whereas HDPP trucks with C rated LTs is 48 psi

Under inflating Es stresses the sidewalls more than it should. Under inflating brought about the whole explorer flipping issue. It wasn't an issue until it was.

 

[pittman]

I think Ford's door sticker is a fantastic guideline for tire inflation. It takes into account the tire architecture and weight of the truck.

Inflating to 80PSI because that's what's on the side of the tire does not.

 

[pittman]

Ford's own PSI ratings for E LT tire ratings would be listed on PB for instance as....
145" WB 43F, 45R (3900, 4150)
157" WB 45F, 45R (4050, 4150)

Here's their C LT stickers for only 7,000 GVWR w/ 3600, 3800
whereas HDPP trucks with C rated LTs is 48 psi

Under inflating Es stresses the sidewalls more than it should. Under inflating brought about the whole explorer flipping issue. It wasn't an issue until it was.

The issue with Firestone tires wasn't solely due to tire inflation and heat. Multiple experts have weighed in over the years and pressure/heat was only identified as one factor amongst many. Certainly, Ford Explorers didn't come with LT tires and the design of the Firestone tires was a big part of the problem. Using this example to justify using higher pressures on LT tires doesn't make sense.

 

[HammaMan]

The issue with Firestone tires wasn't solely due to tire inflation and heat. Multiple experts have weighed in over the years and pressure/heat was only identified as one factor amongst many. Certainly, Ford Explorers didn't come with LT tires and the design of the Firestone tires was a big part of the problem. Using this example to justify using higher pressures on LT tires doesn't make sense.

It's simply a data point, not the basis of the argument of using actual pressure recommendations of both the vehicle and tire manufacturers.

Are you suggesting they're both wrong? and by both, I mean every vehicle and tire manufacturer with LT tires.

 

[jcru1017]

Ford's own PSI ratings for E LT tire ratings would be listed on PB for instance as....
145" WB 43F, 45R (3900, 4150)
157" WB 45F, 45R (4050, 4150)

Here's their C LT stickers for only 7,000 GVWR w/ 3600, 3800
whereas HDPP trucks with C rated LTs is 48 psi

Under inflating Es stresses the sidewalls more than it should. Under inflating brought about the whole explorer flipping issue. It wasn't an issue until it was.

But aren’t the stated amounts maximum air pressure? Does that include towing?

My F150 has a mid travel kit so there is some slight camber which has more contact patch on the inner side of the tires. I run a lower pressure to get the middle and outer side more contact. Yes, it will definitely wear quicker but it it does grip better on the street.

You can see in the picture the white square doesn’t get contact while the rest of the tire in red does

 

[pittman]

It's simply a data point, not the basis of the argument of using actual pressure recommendations of both the vehicle and tire manufacturers.

Are you suggesting they're both wrong? and by both, I mean every vehicle and tire manufacturer with LT tires.

What are you talking about?

The max pressure on the side of a tire is to achieve maximum load. If you're not running maximum load then it makes no sense.

The door sticker takes into account the vehicle weight and tire design. The reason the PB trucks specify higher pressures is because they weigh significantly more. Not because the tire is a LT casing.

If you want to run 80psi be my guest. But don't complain about poor ride, poor handling, poor tire wear, and poor traction. If my tires explode I'll call you first.

 

[HammaMan]

But aren’t the stated amounts maximum air pressure? Does that include towing?

My F150 has a mid travel kit so there is some slight camber which has more contact patch on the inner side of the tires. I run a lower pressure to get the middle and outer side more contact. Yes, it will definitely wear quicker but it it does grip better on the street.

You can see in the picture the white square doesn’t get contact while the rest of the tire in red does

Couldn't tell you anything about your truck as you've got no details on it. I'd still run pressures that are appropriate for your truck's mass regardless of the angle you've chosen to run them at. Also verify both inside and outside wear marks from corning to ensure you're not ignoring excessive slip angle. Given the tread design it won't appear to be an issue as it's a hefty tire. That tire at that exact moment does appear to be over-inflated assuming it was clean and run over a smooth surface.

The max pressure on the side of a tire is to achieve maximum load. If you're not running maximum load then it makes no sense.

The door sticker takes into account the vehicle weight and tire design. The reason the PB trucks specify higher pressures is because they weigh significantly more. Not because the tire is a LT casing.

What are you talking about? I've never said a peep about max tire pressure ratings on tires. The factory XL tires masquerading as SL have 51psi written on them. That wasn't brought up / mentioned in any context. Your brain is reading into things not written.

 

[pittman]

Couldn't tell you anything about your truck as you've got no details on it. I'd still run pressures that are appropriate for your truck's mass regardless of the angle you've chosen to run them at. Also verify both inside and outside wear marks from corning to ensure you're not ignoring excessive slip angle. Given the tread design it won't appear to be an issue as it's a hefty tire. That tire at that exact moment does appear to be over-inflated assuming it was clean and run over a smooth surface.

What are you talking about? I've never said a peep about max tire pressure ratings on tires. The factory XL tires masquerading as SL have 51psi written on them. That wasn't brought up / mentioned in any context. Your brain is reading into things not written.

So what's the significance of the 51psi written on the side of your tire? What does it mean to you?

 

[HammaMan]

So what's the significance of the 51psi written on the side of your tire? What does it mean to you?

Again, reading into something not there. My tires say 80psi.

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