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Tire pressure when changing sizes - Look here

Alxmlr789

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I'm seeing lots of false information both on here and on Facebook regarding tire pressures when going to an LT tire from a P metric so i'd figure I'd post this. The answer is definitely NOT the pressure on the placard, you'll kill both your rolling resistance (MPG) and the outside edge of your tires. Toyo made a chart specifically for this, and it's very helpful. Hopefully, we can make this a sticky!

https://www.toyotires.com/media/2125/application_of_load_inflation_tables_20170203.pdf

In short , you need to look at your OEM tire size and pressure on the door, take that number to the chart for the weight (don't think the weight is on the placard). Take that weight to your new tire size and you'll have your PSI. In my example, it was 285/45/22 @ 36 PSI = 2416lbs. I made the switch to a 35x12.50x20, so I take that 2416 to that tire size which takes me to 43ish PSI (right between 40-45). I run the front at 48 being a little heavier, rear at 43. When i am towing, i bump the rear up to 50PSI.

Let's take another example. Another OEM tire size is 275/55/20 @ 35PSI - which is 2603. Say you switch to a 295/60/20 (seems to be a common size guys go to) you'd take 2603lbs to the 295/60/20. That weight falls smack in the middle of 40-45. Since these are trucks and are heavier in the front you need to look at the GAW to figure out the true PSI for the front and rear axle. But, at least these tables give us a starting place.

Hope this is helpful!!
 

Stryker6040

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I'm seeing lots of false information both on here and on Facebook regarding tire pressures when going to an LT tire from a P metric so i'd figure I'd post this. The answer is definitely NOT the pressure on the placard, you'll kill both your rolling resistance (MPG) and the outside edge of your tires. Toyo made a chart specifically for this, and it's very helpful. Hopefully, we can make this a sticky!

https://www.toyotires.com/media/2125/application_of_load_inflation_tables_20170203.pdf

In short , you need to look at your OEM tire size and pressure on the door, take that number to the chart for the weight (don't think the weight is on the placard). Take that weight to your new tire size and you'll have your PSI. In my example, it was 285/45/22 @ 36 PSI = 2416lbs. I made the switch to a 35x12.50x20, so I take that 2416 to that tire size which takes me to 43ish PSI (right between 40-45). I run the front at 48 being a little heavier, rear at 43. When i am towing, i bump the rear up to 50PSI.

Let's take another example. Another OEM tire size is 275/55/20 @ 35PSI - which is 2603. Say you switch to a 295/60/20 (seems to be a common size guys go to) you'd take 2603lbs to the 295/60/20. That weight falls smack in the middle of 40-45. Since these are trucks and are heavier in the front you need to look at the GAW to figure out the true PSI for the front and rear axle. But, at least these tables give us a starting place.

Hope this is helpful!!

so the GAW on my truck is 3900lb on the front and 4100lb on the rear. Is this the number i input into the conversion?
 

Stryker6040

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Nevermind i think i answered my own question factory tires where a 116t so a 2756 load rating at 36psi converted to a lt295-65-20 i should be around 45psi on the new tires. Let me know if im kn the right track
 

Alxmlr789

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Nevermind i think i answered my own question factory tires where a 116t so a 2756 load rating at 36psi converted to a lt295-65-20 i should be around 45psi on the new tires. Let me know if im kn the right track
Yep you got it.
 

Yogi217

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This is very helpful!

I have a question, on this chart my oem at 275/55/r20 is only rated as 111, but on bridgestone it is 113t, which is a higher rating..

I guess we can use this as a rough estimate. I am considering switching from a P to an LT, so this would be helpful.
 

mtvrwe2003

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This is very helpful!

I have a question, on this chart my oem at 275/55/r20 is only rated as 111, but on bridgestone it is 113t, which is a higher rating..

I guess we can use this as a rough estimate. I am considering switching from a P to an LT, so this would be helpful.

Yogi you can’t go wrong with a LT I love mine and pump them up 55psi.


Sent from my iPhone using Tapatalk
 
U

User_46695

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So I had the OEM Bridgestone Dueler H/L in 275/55/20 113T and just got some Toyo open county AT3s in LT285/60/20 load range E. The tire store set the PSI to 36 which seems really low. Can anyone help me figure the correct PSI out? I cant figure out the chart. Thanks
 

Nukegm426

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Just changing tire types in the same size can effect ideal pressure.... easiest way is to find smooth concrete and grab some chalk. Draw a thick line across the tires side to side and then slowly drive across the concrete a couple tire revolutions. Get out and look at your line... worn in the middle but not the edges? To much air, lower the pressure a little and repeat the process. Worn on the edge but not the middle? To little, add some and repeat. Get as close to even wear across the full width of the tread for maximum tire life. Keep in mind whether it’s this way or just trying the chart mentioned before that the tire light might come on because your outside factory spec. Either get a programmer and change the tire pressure setting or just live with it.
 

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