What tire pressure for these new truck tires?

Mar 16, 2003
I just got some new Good Year Authority tires on my truck. Historically I fill my tires to 35psi but these are way more aggressive then anything I have had on the truck before. A friend said to fill them to 40-45 at least. The tire sidewall say 50PSI max. What would be a good pressure to keep them at while daily driving around town? The truck sits in the garage a lot too . Some time for a few months so the tires are on the same spot all the time. Here are a couple pictures of the tires and the truck is a 1997 1500 half ton GMC Sierra. Thanks for any advice!

Jul 15, 2003
50PSI on the sidewall is the max they can handle. Why would you think you need more pressure than the normal recommended on the door panel? I just got a set of these for my truck, but haven't installed them yet.
Dec 20, 2012
Most likely your new tires are also P-tires with reference-pressure 35 or 36 psi.
The 50 psi then is the maximum allowed cold pressure.
The difference between both is used in the official system, to highen up the reference-pressure for speed and camber angle, with a system depending on speedcode of tire.

For the reference-pressure and -speed ( 160kmph/99mph) the maxload is calculated by tiremakers, and put on sidewall.

So its a standard not calculated advice pressure that 35 psi.
Probably you can have for these oversised tires even about 25 psi safe pressure, so tires wont overheat, driving 99mph.

I can make a pressure/axleload list for you, with my determined extra safe formula and system, and gives 90% of the loadcapacity for 99mph.
Determined that to give max reserve, with still acceptable comfort and gripp.

Then you " ONLY" have to determine the axleloads in your use acurate, the most tricky part in it all.
If carmajer calculates the recomended pressure, he uses the GAWR, and mostly max technical carspeed for that.

Then only when standing still, you can put about 10 psi higher pressure to preven flatt spots, but they dissapear by themselfes on a healty tire, after 15 minutes of driving.

Need next of tire for the list, can be read from sidewall mostly.
1. Maximum load or loadindex
2. Kind of tire to determine that reference-pressure.
3. speedcode would be nice
Feb 22, 2003
Somewhere in the US
Here's my take on tire pressure:

On every vehicle sold in the US, there is a stick, commonly called the placard, that lists the original tire size and the specified pressure for that size. If your tires are the same size 9and that includes the letters before or after the numbers), then that is what you should use. Exception: If there is something about the tires you don't like, then using a higher pressure is OK, but I would suggest not using a lower pressure as that has implications for load carrying capacity, and you don't want a structural failure!

If your tires are a different size (and that includes the letters), then you need to consult the load tables.

I suspect these are LT tires and they are a different size than what is listed on the placard. So unless we know what those 2 sizes are, we can't know how to advise the OP.
Dec 20, 2012
Now I see it too, so thanks.

Googled the tire.
Found 112/109 loadindex and 6pr/LRC/C-load is AT 50 psi referencepressure.
So I was wrong about the P-tires, but still the OEM tires most likely where P, because of the 35psi recomended pressure.

Then I made you the list, assuming rear singleload axle, so the 109 loadindex for dualload axle, I did not use.

In front of psi 100% of loadcapacity calculated for the cold psi, and behind the psi 90% of it.
My advice is to look back in last list.
Given per axle, so dont devide by 2 yourselfes, all done for you.
ONLY have to determine the axleloads acurately, succes with that.

100% of LC/ Cold PSI/ 90% of Loadcapacity

2171 lbs/ 20 psi / 1954 lbs
2265 lbs/ 21 psi / 2039 lbs
2360 lbs/ 22 psi / 2124 lbs/ EUR syst lowest
2454 lbs/ 23 psi / 2208 lbs
2548 lbs/ 24 psi / 2293 lbs
2641 lbs/ 25 psi / 2377 lbs
2735 lbs/ 26 psi / 2461 lbs/US syst lowest
2828 lbs/ 27 psi / 2545 lbs
2921 lbs/ 28 psi / 2629 lbs
3014 lbs/ 29 psi / 2713 lbs
3107 lbs/ 30 psi / 2797 lbs
3200 lbs/ 31 psi / 2880 lbs
3293 lbs/ 32 psi / 2963 lbs
3385 lbs/ 33 psi / 3046 lbs
3477 lbs/ 34 psi / 3129 lbs
3569 lbs/ 35 psi / 3212 lbs/ old recomended
3661 lbs/ 36 psi / 3295 lbs
3753 lbs/ 37 psi / 3378 lbs
3845 lbs/ 38 psi / 3460 lbs
3937 lbs/ 39 psi / 3543 lbs
4028 lbs/ 40 psi / 3625 lbs
4120 lbs/ 41 psi / 3708 lbs
4211 lbs/ 42 psi / 3790 lbs
4302 lbs/ 43 psi / 3872 lbs
4393 lbs/ 44 psi / 3954 lbs
4484 lbs/ 45 psi / 4036 lbs
4575 lbs/ 46 psi / 4117 lbs
4666 lbs/ 47 psi / 4199 libs
4756 lbs/ 48 psi / 4281 lbs
4847 lbs/ 49 psi / 4362 lbs
4938 lbs/ 50 psi / 4444 lbs/ referencepress
5028 lbs/ 51 psi / 4525 lbs
5118 lbs/ 52 psi / 4606 lbs
5208 lbs/ 53 psi / 4688 lbs
5299 lbs/ 54 psi / 4769 lbs
5389 lbs/ 55 psi / 4850 lbs
5479 lbs/ 56 psi / 4931 lbs
5568 lbs/ 57 psi / 5012 lbs
5658 lbs/ 58 psi / 5092 lbs
5748 lbs/ 59 psi / 5173 lbs
5838 lbs/ 60 psi / 5254 lbs
Last edited:
Dec 20, 2012
In the second photo, you can see it is a:

LT265/75-16 Load Range C

So, yes, it is an LT tire and, yes, the max inflation pressure for a Load Range C is 50 psi.
When I look at the 2nd picture again, after the rimmsize its not clear.
Can also be a D-load with higher loadindex. So topicstarter, will you read it from sidewall again, to be certain.
If D load, I have to make a new list, in wich lower loadcapacity's for the same pressure.

Chris B.

Thread starter
Mar 16, 2003
50PSI on the sidewall is the max they can handle. Why would you think you need more pressure than the normal recommended on the door panel? I just got a set of these for my truck, but haven't installed them yet.
They are really nice so far. Not noisy at all.
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May 25, 2005
I always start with the plaque on the door jamb and alter +/- psi here & there according to my driving style and what I might be doing with the vehicle and the passengers/cargo etc.

Have you Krown'd/Fluid Film'd/RustCheck'd the chassis ?