Concerned about new tire purchase!

[62Blazer]

So if it says the max PSI is 50, does that mean I should be fine with say 45 front and 40 rear? I'll rarely haul anything with much weight in the bed if rarely.

Yes. The "max PSI" is just that, the maximum safe pressure you can put in the tires and should never exceed. Inflating the tires to a higher PSI means you are starting to risk tire failure from them blowing out (not saying putting 55 PSI in a 50 PSI max tire is going to cause it to explode because of the safety factor built in....but I'm sure if keep increasing the pressure at some point they will fail). It does not say you need to run that pressure...just not exceed that pressure. The weight rating of the tires is basically a direct correlation to the inflation pressure. The max weight rating of the tire is at the max PSI, so if the tire is rated for 3,000 lbs. max and 50 PSI max that means the tire can support 3,000 lbs. at 50 PSI. As you decrease the inflation pressure (PSI) of the tire the weight rating goes down proportionally. The rule of thumb is if you decrease PSI by 10% you decrease the load rating by 10%. In this case that would be dropping the inflation down to 45 PSI and would decrease the weight rating by 10% also, which would make it around 2,700 lbs. Drop the PSI in half, so 25 PSI, and the weight rating is dropped in half to about 1,500 lbs. **Just to clarify, this is a general rule of thumb to get you in the ballpark. Typically easy to find load inflation tables on manufacturers website that give exact numbers**.
With that said if you have tires rated around 3,000 lbs. each times 4, so around 12,000 lbs., and the truck weighs maybe around 7,500 lbs. That means you only need around 63% of the tires weight rating to support the truck. 63% of 50 PSI is 31 PSI, which means that running in the 40 PSI range is perfectly safe. Keep in mind this is assuming equal weight front to rear. On a pickup when unloaded the front is usually heavier and thus why most people run higher front pressures when unloaded. I generally like to run a little more PSI than what the equation states, but it at least says if you are in the ballpark or not.
As the last statement, the max PSI and load ratings are also for max speed rating of the tire. The higher the speed the more stress/force on the tire. Lower pressure causes the tire to flex as it rotates and the bottom of the tire flexes under the weight of the vehicle. The more it flexes, the more stress and heat build-up. Basically means that the slower you are travelling the less critical and less chance of failure if you are not running the appropriate inflation pressure. If you have a tire really low at 10 PSI you can drive for a really long time at 15 mph with no damage, but go drive down the freeway at 80 mph and it will have permanent damage after a short distance and probably fail (blow out) if you keep going).

 

[CanuckRam1313]

For everyday driving 40psi cold adjusted is a great level to be at for a 1500 wearing LT 10-ply tires, IMHO.

If I am hauling 1,000lb in the bed and/or towing heavy numbers that are within safe and acceptable limits I will run 40psi cold in the front and 50psi cold in the rear.

The Michelin Defender LTX M/S's are a fantastic tire with excellent road manners and respond very well to road conditions and adjusted cold tire pressures.

Empty, stick with 40psi cold for front and rear... with bed load and/or towing, adjust accordingly for the trip and then readjust as required when not on load.

 

[ryanpaulaf1]

Yes. The "max PSI" is just that, the maximum safe pressure you can put in the tires and should never exceed. Inflating the tires to a higher PSI means you are starting to risk tire failure from them blowing out (not saying putting 55 PSI in a 50 PSI max tire is going to cause it to explode because of the safety factor built in....but I'm sure if keep increasing the pressure at some point they will fail). It does not say you need to run that pressure...just not exceed that pressure. The weight rating of the tires is basically a direct correlation to the inflation pressure. The max weight rating of the tire is at the max PSI, so if the tire is rated for 3,000 lbs. max and 50 PSI max that means the tire can support 3,000 lbs. at 50 PSI. As you decrease the inflation pressure (PSI) of the tire the weight rating goes down proportionally. The rule of thumb is if you decrease PSI by 10% you decrease the load rating by 10%. In this case that would be dropping the inflation down to 45 PSI and would decrease the weight rating by 10% also, which would make it around 2,700 lbs. Drop the PSI in half, so 25 PSI, and the weight rating is dropped in half to about 1,500 lbs. **Just to clarify, this is a general rule of thumb to get you in the ballpark. Typically easy to find load inflation tables on manufacturers website that give exact numbers**.
With that said if you have tires rated around 3,000 lbs. each times 4, so around 12,000 lbs., and the truck weighs maybe around 7,500 lbs. That means you only need around 63% of the tires weight rating to support the truck. 63% of 50 PSI is 31 PSI, which means that running in the 40 PSI range is perfectly safe. Keep in mind this is assuming equal weight front to rear. On a pickup when unloaded the front is usually heavier and thus why most people run higher front pressures when unloaded. I generally like to run a little more PSI than what the equation states, but it at least says if you are in the ballpark or not.
As the last statement, the max PSI and load ratings are also for max speed rating of the tire. The higher the speed the more stress/force on the tire. Lower pressure causes the tire to flex as it rotates and the bottom of the tire flexes under the weight of the vehicle. The more it flexes, the more stress and heat build-up. Basically means that the slower you are travelling the less critical and less chance of failure if you are not running the appropriate inflation pressure. If you have a tire really low at 10 PSI you can drive for a really long time at 15 mph with no damage, but go drive down the freeway at 80 mph and it will have permanent damage after a short distance and probably fail (blow out) if you keep going).

Man thank you so much for all that info. I must say I feel pretty ignorant on PSI stuff for tires but that’s ok, we all learn something new sometimes. So thank you for all that good info. I will put that in my mental toolbox for future reference.

 

[G. Mcpherson]

Toyo Tire has a Good load chart. Check it out.

 

[olyelr]

Toyo Tire has a Good load chart. Check it out.

https://www.toyotires.com/media/pxcjubjs/application_of_load_inflation_tables_20200723.pdf

 

[huntergreen]

Man thank you so much for all that info. I must say I feel pretty ignorant on PSI stuff for tires but that’s ok, we all learn something new sometimes. So thank you for all that good info. I will put that in my mental toolbox for future reference.

I wouldn’t deviate from what ever load rating came on the stock tires.

 

[ryanpaulaf1]

I wouldn’t deviate from what ever load rating came on the stock tires.

The tires I currently have for sure are NOT what came on if stock. The previous owner had them put on at some point, but I think they came stock with 275/70/17. I think from everything I've researched and people telling me on here I'll be just fine. I treat her like a baby anyway lol.

 

[olyelr]

I wouldn’t deviate from what ever load rating came on the stock tires.

Bad advice when his new tires have a max psi of 50.

 

[62Blazer]

The tires I currently have for sure are NOT what came on if stock. The previous owner had them put on at some point, but I think they came stock with 275/70/17. I think from everything I've researched and people telling me on here I'll be just fine. I treat her like a baby anyway lol.

The Power Wagons, as far as I know, have always come with 285/70R17 tires. Believe BFG AT's originally and then Goodyear Duratracs in a D load rating for many years. These have a load index of 121 which is the same as the tires listed by the original poster of this thread.

 

[Hydrasport23]

If you are looking at the tire specs that are on the sidewall, you may want to learn what that info is about. The vehicle weight and a few other pieces of info is what the manufacturer uses to create the vehicle specific tire info label found one the door post. They may also give optional tire sizes for your vehicle. The info on the tires sidewall are the results of certain test results for certification which allows that tire to sold in the U.S. Hence, tire pressure on the sidewall is the pressure used during the 60 minute test with the weight specified during the 90 mph, 60 minute test that is required by the NHTSA. If that tire size is not listed as an optional size, you are on your as for as air pressure and use.

 

[lpennock]

Easy starting point for your tire pressure. Pull the tire size and pressures off the door jam and plug them into this Tire Pressure Calculator. I would run the rears lower than the door jam pressure as that pressure assumes the truck is fully loaded. For a LT315/70-17 I would probably start at 35psi which wii support a 2535x2=5070lb axle weight.

 

[62Blazer]

Easy starting point for your tire pressure. Pull the tire size and pressures off the door jam and plug them into this Tire Pressure Calculator. I would run the rears lower than the door jam pressure as that pressure assumes the truck is fully loaded. For a LT315/70-17 I would probably start at 35psi which wii support a 2535x2=5070lb axle weight.

I understand what you are saying. However just to make it clear for somebody else maybe reading this post, they are not saying to run the tire pressures shown on the door jam which only pertain to the original tires size and load rating, but the posted calculator will "translate" the pressure of the original tires to what is needed for a different size and/or load rating tire.

The calculator can be useful if you have an "idea" air pressure for the current tires (not the door sticker, but what works the best in real life) and want to get a baseline for a different size or load rating tires.

 

[lpennock]

I understand what you are saying. However just to make it clear for somebody else maybe reading this post, they are not saying to run the tire pressures shown on the door jam which only pertain to the original tires size and load rating, but the posted calculator will "translate" the pressure of the original tires to what is needed for a different size and/or load rating tire.

The calculator can be useful if you have an "idea" air pressure for the current tires (not the door sticker, but what works the best in real life) and want to get a baseline for a different size or load rating tires.

The Door jam pressure is usually pretty close to ideal with a margin of error on the front axle. For my 3500 the door jam was 80 psi but after weighting the truck and looking at the load tables the minimum pressure for the Axle Weight was 72psi. So now I run about 78. Unless the person is going to get the truck weighted at a CAT scale and look up the load tables I will still recommend the door jam pressure and tire size as the starting point for the calculator.

The rear axles aren't close unless the truck is loaded as TRA managed to get a ruling passed that required the door jam pressure to be for the maximum GAWR.

Both my 06 3500 and 18 DRW came in under 3500lb unloaded axle weights. So when I make a rear psi recommendation I will use 2000lb (margin of error) to look up the pressure in the load tables. Since the load tables I have for a LT don't go below 35 psi I won't recommend below 35psi even though the tires can be run lower if someone does calculation.

 

[62Blazer]

The Door jam pressure is usually pretty close to ideal with a margin of error on the front axle. For my 3500 the door jam was 80 psi but after weighting the truck and looking at the load tables the minimum pressure for the Axle Weight was 72psi. So now I run about 78. Unless the person is going to get the truck weighted at a CAT scale and look up the load tables I will still recommend the door jam pressure and tire size as the starting point for the calculator.

The rear axles aren't close unless the truck is loaded as TRA managed to get a ruling passed that required the door jam pressure to be for the maximum GAWR.

Both my 06 3500 and 18 DRW came in under 3500lb unloaded axle weights. So when I make a rear psi recommendation I will use 2000lb (margin of error) to look up the pressure in the load tables. Since the load tables I have for a LT don't go below 35 psi I won't recommend below 35psi even though the tires can be run lower if someone does calculation.

The tire pressures listed are ideal pressures if you are running at the maximum load of the truck. Having the rear tires at 80 psi on an empty pickup truck is in no way ideal. Fully loaded, I will agree it is close.......but not empty.

 

[lpennock]

The tire pressures listed are ideal pressures if you are running at the maximum load of the truck. Having the rear tires at 80 psi on an empty pickup truck is in no way ideal. Fully loaded, I will agree it is close.......but not empty.

We are in total agreement on the Rears. The jam pressures are way high for unload.

I'm saying that the fronts are close enough as there is only about 5-600 lb axle weight difference between unloaded and rated GAWR, at least with a Cummins up there.

 

[olyelr]

The Door jam pressure is usually pretty close to ideal with a margin of error on the front axle. For my 3500 the door jam was 80 psi but after weighting the truck and looking at the load tables the minimum pressure for the Axle Weight was 72psi. So now I run about 78. Unless the person is going to get the truck weighted at a CAT scale and look up the load tables I will still recommend the door jam pressure and tire size as the starting point for the calculator.

The rear axles aren't close unless the truck is loaded as TRA managed to get a ruling passed that required the door jam pressure to be for the maximum GAWR.

Both my 06 3500 and 18 DRW came in under 3500lb unloaded axle weights. So when I make a rear psi recommendation I will use 2000lb (margin of error) to look up the pressure in the load tables. Since the load tables I have for a LT don't go below 35 psi I won't recommend below 35psi even though the tires can be run lower if someone does calculation.

The door jam sticker goes right out the window when you swap different size tires with different load ratings. Period. They no longer exist lol.

 

[lpennock]

The door jam sticker goes right out the window when you swap different size tires with different load ratings. Period. They no longer exist lol.

Not so they are the data to use the calculator with.

 

[ryanpaulaf1]

I've been running 40 front and about 35-38 rear for about 2 weeks now and I personally love the way they feel. The truck rides so so much better than my previous E rated tires. I love them so far. Can't wait for the winter time now.