Questions about tire psi

[weatherherk]

Hopefully you guys can school me a bit on what the optimal psi is for the tires. Seen a few posts regarding people running their tires at different psi, and was wondering what would work for my needs.

What I would like to gain is a bit of ride comfort and gas mileage. Most of this trucks life will be local or long distance highway, most of the time with just a payload in the bed, although I do tow on the turnpike intermittently. If any of y’all have any tips would be greatly appreciated!

i'd go by what the inside driver door label says for the recommend tire pressure

 

[weatherherk]

According to the official Ford Pass app which I am looking at right now, Recommended Cold Pressure:
60 front, 80 back

I am running 52ish front, and 68ish back.

so much for 60 and 80...lol

 

[Father of One]

This is a 35x12.50 Toyo MT on a 2007 Ram 2500 diesel 4x4. The tires had 59,498 miles when this picture was taken. When unloaded, I run between 38-40 front and 32-35 rear on this truck.

My method is to scale the truck so that I can estimate the corner weight, consult a tire load vs. psi chart to get a baseline, chalk test, and then make minor adjustments as they wear.

My take is that the psi in the tire needs to match the actual load on the tire. This will vary depending on whether you are loaded or empty.

 

[TonyJ]

The chart title says: "Corresponding tire load capacity"

It doesn't say front, rear, per axle, or whatever.
I need a plain English translation like - Curb weight + payload.
I think I can divide by four.

Aircraft weight ratings are simpler than pickup trucks'!

Dividing by 4 doesn't really help. Unloaded a pickup truck will always have a lot more weight on the front tires, than on the rear. I'm curious, has anyone scaled their truck by axle?

 

[oops]

Dividing by 4 doesn't really help. Unloaded a pickup truck will always have a lot more weight on the front tires, than on the rear. I'm curious, has anyone scaled their truck by axle?

The Tremor has about 3500# on the rear axle with a driver, passenger, and fluids (1750# per rear tire.)

Stock tire pressure

TonyJ - I’m no expert, but for me the low tire pressure warning was a little annoying at startup, but one “ok” press of the button and it goes away. I could live with the tiny amber icon on the dash…never really bothered me. Actually got used to seeing “checking” all four corners at startup...

www.fordtremor.com

 

[oops]

The Tremor has about 3500# on the rear axle unloaded (1750# per tire.)

Building on that for myself (Godzilla engine):

• My unloaded rear tire load is ~1750#
• My uloaded front tire load is ~2000#
• My maximum trailer tongue weight is ~2400#
• My maximum total payload is 2874#
• My maximum loaded rear tire load is ~2312#

Anecdotally, these tires start to get a bit too squishy for me in the front under 45 psi, suggesting I prefer ~45% more pressure than is required by these tires to carry their load. As such I will run:

• Unloaded:
  • 45 psi front
  • 40 psi rear
• Fully Loaded:
  • 45 psi front
  • 50 psi rear

I currently run 50 psi front, 65 psi rear at all times. That’s clearly excessive. And I'm towing less frequently recently, so it makes sense to give up one-pressure convenience for better ride quality when unloaded. Airing up 10 psi takes 10 minutes with my battery operated inflator. It takes me longer than that to hook up and load a trailer.

 

[Loshad]

45/40 sounds awfully low. I'd like to see a chalk test on that.

 

[TonyJ]

Building on that for myself (Godzilla engine):

• My unloaded rear tire load is ~1750#
• My uloaded front tire load is ~2000#
• My maximum trailer tongue weight is ~2400#
• My maximum total payload is 2874#
• My maximum loaded rear tire load is ~2312#

Anecdotally, these tires start to get a bit too squishy for me in the front under 45 psi, suggesting I prefer ~45% more pressure than is required by these tires to carry their load. As such I will run:

• Unloaded:
  • 45 psi front
  • 40 psi rear
• Fully Loaded:
  • 45 psi front
  • 50 psi rear

I currently run 50 psi front, 65 psi rear at all times. That’s clearly excessive. And I'm towing less frequently recently, so it makes sense to give up one-pressure convenience for better ride quality when unloaded. Airing up 10 psi takes 10 minutes with my battery operated inflator. It takes me longer than that to hook up and load a trailer.

Soop, how did you come up with those weights? The difference between front and rear are a lot narrower than I expected.

 

[oops]

Soop, how did you come up with those weights? The difference between front and rear are a lot narrower than I expected.

Using the scale readings from @DIG (who has the diesel engine) in the link I posted above.

 

[TonyJ]

Using the scale readings from @DIG (who has the diesel engine) in the link I posted above.

Thanks a bunch! When I was a driver, you could always count on the CAT scales to be right. Still pretty amazed at how close the weights are, & I'd imagine because the 6.7 is a little heavier, the weights would even be closer on my Godzilla.

 

[donmatteo]

I run the standard 60 in the nose and 80 in the rear. I’m more concerned about tire wear than ride comfort. After all it is a Heavy Duty truck, not a luxury sedan. If you go to low with these tall profile tire they become squishy and tend to roll from side to side. Ultimately it’s your decision, but I’d run what the sticker in the door says. They pay those engineers big money to figure this stuff out

While this may be true for a stock suspension, this isnt true on, in my case, a Carlie suspension. The stocks and springs are turned for lower pressures.

 

[Spoonman]

As an experienced race car driver, I can tell you not to obsess over cold pressures. You need to be concerned with hot pressures. The reason is once your tires warm up, which does not take long, thats the effective tire pressure you run. This depends on the ambient conditions, driving style, tire compound, asphalt temp, asphalt texture, etc., you will see a varying degree of pressure fluctuations. It's not uncommon for certain track tires once up to temp, for pressures to rise up 8-12 psi. I use a thermometer to measure the temps across the whole tread to determine if my pressures are correct as you want even heat distribution. It's one way to see how pressures affect wear.

Recently I towed my travel trailer 300miles with ambient temps in the 50's, cruising at 65mph on fairly straight highway. Cold pressures at the start of my trip were 60/70. Pressures rose to 70/80 once tires were up to temp. You can see the numbers below from the CAT scale.

My advice is to watch your pressures rise and stabilize while driving on your commute and adjust your cold pressures accordingly. If your target hot pressures are 50/55, you may need to start with cold pressures at 45/50. Savvy?

2022 F250 6.7L
JAYCO TT 39' bumper pull
Equalizer WD/Anti sway hitch

My payload sticker says 2738#
F250 GVW=8062#
F250 GVW(loaded)=9820#
Payload 1758# at the scale
-cargo = 600#
- tongue weight = 1158#
Travel trailer GVW = 11,158#

 

[Potato Wilson]

Seems to me that optimum tire pressures would be to run higher in the front than in the rear when unloaded. Especially with the diesel, there is a lot more weight on the front axle than the rear when empty. Plus the load caused by steering. With that in mind it makes sense to drop the pressure in the rear to soften the ride a little and increase traction, again while empty.
In all honesty after messing around with various pressure combos I’ve settled on running 71-72 front and rear all the time. Truck feels firm and planted on mountain highways while empty, and at the same time is also very stable while towing a10k lb trailer.

 

[ccw]

As an experienced race car driver, I can tell you not to obsess over cold pressures. You need to be concerned with hot pressures. The reason is once your tires warm up, which does not take long, thats the effective tire pressure you run. This depends on the ambient conditions, driving style, tire compound, asphalt temp, asphalt texture, etc., you will see a varying degree of pressure fluctuations. It's not uncommon for certain track tires once up to temp, for pressures to rise up 8-12 psi. I use a thermometer to measure the temps across the whole tread to determine if my pressures are correct as you want even heat distribution. It's one way to see how pressures affect wear.

Recently I towed my travel trailer 300miles with ambient temps in the 50's, cruising at 65mph on fairly straight highway. Cold pressures at the start of my trip were 60/70. Pressures rose to 70/80 once tires were up to temp. You can see the numbers below from the CAT scale.

My advice is to watch your pressures rise and stabilize while driving on your commute and adjust your cold pressures accordingly. If your target hot pressures are 50/55, you may need to start with cold pressures at 45/50. Savvy?

Really appreciate these thoughts, and honestly it makes a lot of sense to me. Though it naturally leads one to ask: why do all manufacturers consistently quote cold tire pressures?

Is it because it’s easier for the end user? Are they legally required to do cold pressures on the door placard? If so, why is the law that way?

 

[MCTremor]

I run the standard 60 in the nose and 80 in the rear. I’m more concerned about tire wear than ride comfort. After all it is a Heavy Duty truck, not a luxury sedan. If you go to low with these tall profile tire they become squishy and tend to roll from side to side. Ultimately it’s your decision, but I’d run what the sticker in the door says. They pay those engineers big money to figure this stuff out

This is a really good point. Just look at the cause for all those Explorers that had tread separation on the Firestone resulting in flipping over and blow outs. Part of the reason was the tires were suggested to be aired down to an unsafe level for the vehicle weight and distribution.

Todays tires are better and this led to big manufacturers doing a little better about their suggestions.

 

[Loshad]

"why do all manufacturers consistently quote cold tire pressures?"

So we're all using the same baseline and because it's safer to run
a little higher than it is to run lower? Besides, who's gonna stop
to check their pressures after they're on the road a while?