Tire Pressure Debate.
04-14-2016, 01:04 AM
#1
Tire Pressure Debate.
Took a buddy up to my ranch this past weekend. Fell into a conversation about tire pressure.
I recently leveled my 15ScrewFx4, and tossed on a set of Toyo ATIIs 295/65r20s. Discount Tire blasted them to 40psi and they rode like ****. I dropped them to 32psi, and made all the difference in the world. MPG has been mildly unaffected.
Anyhow, buddy says I should rock whats on the door jamb placard. I say that is way too high. His theory is larger tire, more PSI. I vote the opposite, but I really dont know where the pressure should be.
The tires are stamped with a max pressure of 80psi. I ran the same tire in a 285/75/18s on my F350, with 65psi front, and 80psi rear.
Which one of us is correct? Both wrong? Bueller?
I recently leveled my 15ScrewFx4, and tossed on a set of Toyo ATIIs 295/65r20s. Discount Tire blasted them to 40psi and they rode like ****. I dropped them to 32psi, and made all the difference in the world. MPG has been mildly unaffected.
Anyhow, buddy says I should rock whats on the door jamb placard. I say that is way too high. His theory is larger tire, more PSI. I vote the opposite, but I really dont know where the pressure should be.
The tires are stamped with a max pressure of 80psi. I ran the same tire in a 285/75/18s on my F350, with 65psi front, and 80psi rear.
Which one of us is correct? Both wrong? Bueller?
04-14-2016, 01:13 AM
#2
Senior Member
The debate is over. The correct way to determine your tire pressure can be found here. https://www.toyotires.com/tires-101/...flation-tables The door placard is useless when you convert P rated tires to LT rated tires or any other tire size for that matter. The pressure is based upon load ratings. The correct LT tire pressure will always be higher than a comparable P tire.
ON EDIT: Another important point stated in the above reference - The load rating on a P rated tire installed from the factory or aftermarket for light trucks is reduced by a factor of 1.1 (i.e. Tire manufacturer load rating (P rated) is 3000 lbs. and the tire is installed on a truck then the reduced rating is 2727 lbs.). Running you tire pressure 3-4 PSI higher than the placard will compensate a little for the drop in load rating.
ON EDIT: Another important point stated in the above reference - The load rating on a P rated tire installed from the factory or aftermarket for light trucks is reduced by a factor of 1.1 (i.e. Tire manufacturer load rating (P rated) is 3000 lbs. and the tire is installed on a truck then the reduced rating is 2727 lbs.). Running you tire pressure 3-4 PSI higher than the placard will compensate a little for the drop in load rating.
Last edited by GMC to Ford; 04-14-2016 at 09:11 AM.
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04-14-2016, 03:24 AM
#3
Also keep ion mind that the door placard recommended pressure is based on the assumption you carry a old most of the time; the manufacturer has to make some assumptions when we they do this. I was in the tire business for several years, and it's one of the things we learned. I can tell when I've had my tires rotated and the bump the pressure up to 35 psi; it rides hard. Ilower them back don to 32, and all is smooth again.
You can also monitor your tire wear; it will not lie. If you are getting excessive tread wear in the middle of the tire, then your air pressure is too high for you normal load. The reverse will be true if your pressures are too low...this will result in excessive edge wear.
For most who don't carry anything, 32-33 psi works in most cases.
You can also monitor your tire wear; it will not lie. If you are getting excessive tread wear in the middle of the tire, then your air pressure is too high for you normal load. The reverse will be true if your pressures are too low...this will result in excessive edge wear.
For most who don't carry anything, 32-33 psi works in most cases.
04-14-2016, 08:14 AM
#5
Senior Member
First, the door placard is for the tires that came with the truck. So your buddy is wrong, doesn't know what he is talking about.
Second, you bought LT tires. Per Toyo's website, the ONLY ATII in 295/65R20 is the LT tire, which as you note is an 80 pound max PSI (most P tires are 44 pound max). As noted by GMC to Ford, Toyo's table will tell you the proper PSI.
Without using the table, I'd guess you'll be in the mid 40s to 50 without a load.
Second, you bought LT tires. Per Toyo's website, the ONLY ATII in 295/65R20 is the LT tire, which as you note is an 80 pound max PSI (most P tires are 44 pound max). As noted by GMC to Ford, Toyo's table will tell you the proper PSI.
Without using the table, I'd guess you'll be in the mid 40s to 50 without a load.
Last edited by Ricktwuhk; 04-14-2016 at 08:18 AM.
04-14-2016, 08:17 AM
#6
The debate is over. The correct way to determine your tire pressure can be found here. https://www.toyotires.com/tires-101/...flation-tables The door placard is useless when you convert P rated tires to LT rated tires or any other tire size for that matter. The pressure is based upon load ratings. The correct LT tire pressure will always be higher than a comparable P tire.
Great information
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04-14-2016, 08:49 AM
#7
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04-14-2016, 10:22 AM
#9
Member
The debate is over. The correct way to determine your tire pressure can be found here. https://www.toyotires.com/tires-101/...flation-tables The door placard is useless when you convert P rated tires to LT rated tires or any other tire size for that matter. The pressure is based upon load ratings. The correct LT tire pressure will always be higher than a comparable P tire. ON EDIT: Another important point stated in the above reference - The load rating on a P rated tire installed from the factory or aftermarket for light trucks is reduced by a factor of 1.1 (i.e. Tire manufacturer load rating (P rated) is 3000 lbs. and the tire is installed on a truck then the reduced rating is 2727 lbs.). Running you tire pressure 3-4 PSI higher than the placard will compensate a little for the drop in load rating.
