Tire pressure question

[SixPac]

I have a 2001, 4X4, Quad and tow an enclosed car hauler, 7,500 lbs. , loaded. I have E rated tires, 265/16. For max loading the tires say to inflate at 80lbs. , cold.



Question: Should I run at 80 lbs. all the time or just when max loaded? 80 seems very high, I ran at 65 lbs last time I towed. Will that hurt anything. They (tires) didn't look too low. When I attach my trailer there is very little tounge weight, it hardly even depressess the rear leaf springs at all.



Your comments would be welcome.



Thank you,

 

[Okie-Go]

I would say you are real close to the money. Not long ago there was a thread about this and someone had a formula for pressure/axle weight and tire max. inflation. When loaded I run 75 rear and 60 in the front. I normally run 60 without the trailer. I also have a 66 galllon aux. tank. Remember it says maximum,you are not at maximum. I know a guy that runs 80 on all corners cause he don't want to air up and let down the pressure of his tires everytime he hooks to a trailer. I saw his tires and they looked like they were wearing very well for the amount of miles on them.

 

[dresslered]

Wheew! I don't know about you 2500 guys, but if I ran my dually at 80-psi empty, I would bounce right off of the mountain. Use 80-psi when I'm carrying the slide-in though.

 

[MJawsman]

The 80 PSI is at max rated load. If memory serves me, max load is a little over 3000 lbs per tire. If you don't have 6000 lbs over the rear 1/2 of your truck, there is no need to run 80 psi. However, lower pressures also can result in more side sway, so you may want to experiment with pressure while towing. Personally, I never run less than 50 PSI in my 265/75R16's-loaded or empty. Another point to consider is that with 80 PSI, you have a smaller contact patch on the pavement. If it's raining, you can end up breaking traction. Compound that lack of traction with a panic stop, and you can see why air pressure is such an important issue.

 

[ASchwartz]

New Michelins

I purchased new tires last week (265/75/16/E). Discount Tires inflated them to 60psi. I noticed that I was not getting full contact with the road until I lowered the front to 50psi and the back to 40 psi. Note: This is unloaded.



Before this I was running 235/85/16/E at 55psi all around, also unloaded.

 

[MJawsman]

That sounds about right. I know I've got 60 pounds in my rears and about 65-70 up front. Wear is good so far (28K), but unless I'm unloaded for an extended period, I usually don't run less than 50 in the rear. Up front is a different story since I hate that "flat" look.

 

[Dieselnerd]

Here is the Michelin load range E tire capacity chart that I saved from someones earlier post. Sorry, I can't remember who it was.





1= Recommended Tire Pressure psi



2= Tire Load Lbs.



3= % Maximum Tire Load Capacity



4= Total Axle Weight



47 2000 58. 6% 4000

48 2050 60. 0% 4100

49 2100 61. 5% 4200

50 2150 63. 0% 4300

52 2200 64. 4% 4400

53 2250 65. 9% 4500

54 2300 67. 3% 4600

55 2350 68. 8% 4700

56 2400 70. 3% 4800

57 2450 71. 7% 4900

59 2500 73. 2% 5000

60 2550 74. 7% 5100

61 2600 76. 1% 5200

62 2650 77. 6% 5300

63 2700 79. 1% 5400

64 2750 80. 5% 5500

66 2800 82. 0% 5600

67 2850 83. 5% 5700

68 2900 84. 9% 5800

69 2950 86. 4% 5900

70 3000 87. 8% 6000

71 3050 89. 3% 6100

73 3100 90. 8% 6200

74 3150 92. 2% 6300

75 3200 93. 7% 6400

76 3250 95. 2% 6500

77 3300 96. 6% 6600

78 3350 98. 1% 6700

80 3400 99. 6% 6800

 

[RDavidson]

p.s.i. don't know

I have a 1993 D-250 4X2. I run Bridgestone highway treads on the front and Bridgestone M/S lugs on the rear. About 50% of the time I pull a tandem axle bobcat trailer on a pintle hitch that normally weighs between 8000# to 8500#. I don't have time to adjust tire pressure every time I hook up. The one thing I've found out is that no matter what you run, tire wear is the best gauge of tire inflation. If the tires wear EVENLY across the surface of the tread, your tires are properly inflated. Your contact patch is at its max and so is your traction, handling, tire wear and fuel mileage. Assuming your alignment is correct its easy to get the tires right. Start at 60 psi and drive. Trust your butt, if it feels mushy and pushes out in the corners (which it probably will) add air to the front. I run 75 psi front and 65 psi rear on load range "E" 16"ers. Remember the inner & outer edges of the fronts will wear a little more from cornering. Trust your eyes for the rest. I weigh in between 5200# - 6000# depending on what equipment is on the truck. That puts my gross in the 16,000+ range with the trailer on a 3/4 ton. I drive 30,000 to 35,000 miles a year and buy tires, in pairs, every 18 - 24 months. If you do the math, it works, and works well. I have never ruined a tire from running under inflated or blown one from being over inflated. You will ride a little tight when you're empty but remember, it's not a cadi, it's a truck!

 

[MidwestMotorman]

old trick

You can try an old trick. You can use chalk or a grease pencil to make a mark across the tread. Go test drive the truck with/without the trailer and see how much of the mark is worn off. If the center is worn off, air down. If the sides are worn off, air up. If it is all wore off, either the pressure is right or you were smoking the tires.



This is an old trick someone else mentioned a while ago. You can play with different loads and see how your pressure should be set. Make sure you drive long enough so the tires can warm up.



Happy towing