Tire pressure on LT tires

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So I replaced my OE tires with LT tires last fall but kept the stock size. Wondering what everybody likes to do for tire pressures in this case? I have been running 48psi as that is what a couple calculators have recommended but I am seeing anywhere from 48-50psi as the recommended pressure. Tire shop wants to put them at the door sticker pressure of 35psi, but that was for a 116T load tire not an E range.

Door sticker: 275/65r18 116T 35psi (all four)
New tires: LT275/65r18 123S

I have attached three different online calculators but to me it makes sense that the pressure required *could* change since the two tires are designed with different load ranges and pressure requirements. Interestingly running 48psi for the past 8 months I seem to experienced rather even wear so unless there are compelling reasons to do otherwise that is what I intend to continue doing.

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So I replaced my OE tires with LT tires last fall but kept the stock size. Wondering what everybody likes to do for tire pressures in this case? I have been running 48psi as that is what a couple calculators have recommended but I am seeing anywhere from 48-50psi as the recommended pressure. Tire shop wants to put them at the door sticker pressure of 35psi, but that was for a 116T load tire not an E range.

Door sticker: 275/65r18 116T 35psi (all four)
New tires: LT275/65r18 123S

I have attached three different online calculators but to me it makes sense that the pressure required *could* change since the two tires are designed with different load ranges and pressure requirements. Interestingly running 48psi for the past 8 months I seem to experienced rather even wear so unless there are compelling reasons to do otherwise that is what I intend to continue doing.

View attachment 104693View attachment 104693View attachment 104694View attachment 104695
Use the load tables:
Screen Shot 2022-06-20 at 11.56.22 PM.png


It looks like what you posted shows that the 116 for the 275/70R18 applies the same to the 275/65R18 (not listed in the Toyo guide):
Screen Shot 2022-06-20 at 11.59.21 PM.png


Adjusting it for being a P-Metric, per the first pic from Toyo, that yields 2,435lbs as the load carrying capacity of your OE tires.

Now, we need to match/exceed that, which appears to happen at 50PSI:
Screen Shot 2022-06-21 at 12.04.00 AM.png


So, yes, 48-50psi does seem right.
 
Believe it or not my old 89 Sierra calls for LT tires, the door says 50 psi but that makes for a pretty rough ride so I found 45 psi to be a better ride and they have been wearing evenly according to my gauge.

 
What loadrange is your new LT
C-LOAD AT 55 or 50 psi
D-load At 65psi.
E-Load AT 80 psi.

Read back and already saw E- load is loadindex 123

35psi was the reference pressure of Standard load P-tire( the given list here gives 36psi, used in european system) and is nowadays often given. If calculated with the official european formula with use of the GAWR's , best with a reserve first added, pressure most likely lower.

But OK, I will calculate what maxload belonging to loadindex 116 = 2750lbs would calculate for E- load LI 123= maxload 3420lbs AT 80psi.

Gives 60.9 so 61 psi.
And thats 25 psi higher!!!

But again, if calculated with GAWR's it can probably be lower , mayby Capriracers 36+15= 51 psi.

I used the official european calculation, wich is since 2006 also used in US for P-tires, and should also be used for LT.

You also go 1 speedcode back ( from T to S. Rule is that max speed of tire must be the same or higher then max technical car speed. Even if you never use that speed.

I went with my calculation from pressure calculated for 99mph( 160kmph) wich is the speed the maxload is calculated for, from speedcode Q to V.
This could give some difference, I dont know for what speed your pressure is determined.
 
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Checked the pressure/loadcapacity list for the P-tire that Overkill gave in post #4.

Apeared to be calculated with the old calculation for P-tires with hight/width division /50 and lower.
Your sise is a /65 .
But that for /50 and lower is a bit saver, but stil leads to higher loadcapacity's then the official European calc.

26psi gave 2227 lbs loadcapacity, in that list.
Official european calc gives 2119 lbs loadcapacity, so more then 100lbs lower a tire for 26 psi.

It would give about 10% more deflection, so heatproduction a cycle, using 26psi for 2227 lbs, then for 2119lbs.
 
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Checked the pressure/loadcapacity list for the P-tire that Overkill gave in post #4.

Apeared to be calculated with the old calculation for P-tires with hight/width division /50 and lower.
Your sise is a /65 .
But that for /50 and lower is a bit saver, but stil leads to higher loadcapacity's then the official European calc.

26psi gave 2227 lbs loadcapacity, in that list.
Official european calc gives 2119 lbs loadcapacity, so more then 100lbs lower a tire for 26 psi.

It would give about 10% more deflection, so heatproduction a cycle, using 26psi for 2227 lbs, then for 2119lbs.
not sure where you were going with your posts it makes no sense to me.
Question was answered aprox 3x

his stock tires were at 35psi. why would he be running 26psi or anything? you appear to have some sort of conversion error
 

Answer to post #10
In Post #8 I first gave answer that 61 psi should be used, higher then others wrote.

In Post #9 , I warn that the list given is old, because given loadcapacity for the pressure is to high
Since 2006 US uses for P-tires the better calculation for those lists, that Europe uses for all kind of tires for decades.
But still you can find those old lists on internet.
 
Wow. I need to add some air to my tires on my Tundra. I recently replaced wheels and tires, bought a set of pull-offs the guy had JUST put on his. I went from P tires to LT. I don't drive it daily, so I haven't done much harm. Been running them at 40 psi and I've always thought they looked droopy. I'm going to go to 50 psi.
 
If you give GAWR'S,and max speed you use, and wont go over for even a minute, I can calculate fort that. If carmaker calculates it, they also use the GAWR'S and max technical car speed( topspeed in the books.
 
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