2nd Gen Non-Engine/Transmission Tire Pressure

[Hohn]

Hey all! My first post to the TDR forum (newbie). I am also a newbie when it comes to diesels, though I have worked on (and engineered) gas engines for years.

Now that I have my shiny new truck, I want to learn how to do things right.

The tire pressure placard in my truck says 65psi front, 80 psi rear. This seems very high to me because I am run my rig empty 95% of the time (for now). With the 8800# GVWR package and E load range tires, do I NEED this kind of pressure, even empty? My truck has the 265/75R16E tires.

Basically, I need to know: 1) What tire pressure I should use running mostly empty for max tire life, and 2) what pressure change do I need (if any) when I step up to the 285/75R16 rubber.



Thanks TDR for a great forum!

 

[Dane]

Welcome!



I run my stock tires 55 front and 52 rear unloaded. When hauling the cabover on pavement it's 70/70. Offroad with the cabover is 25 front and 30 rear. I have the 265/75/16 Michelin M/S



IMO, these trucks, especially the 4x4 are very sensitive to tire pressure for ride and handling. Experimenting with different pressures is probably worth the effort in my book.

 

[Dieselnerd]

Here's a chart that I copied from the TDR website quite some time ago.



Below is a table for the E rated Michelin tire.



Over/Under inflation can be dangerous, and does shorten the

tire life. KNOW the loaded weight and inflate accordingly.

Michelin Tire gave me the formula that computes the various

PSI.





Recommended Tire Pressure psi



Tire Load Lbs.



% Maximum Tire Load Capacity



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

 

[FAllen]

Been running mine 55 front and 40 rear empty. Rides well and drives nicely.



Fred

 

[dan_gilson]

You can get your truck weighed and follow the chart or use a less scientific way: Check the wear patterns at rotation (oil change time). I rotate at every oil change. I check the wear pattern and adjust pressure as needed. What you are looking for is even wear across the entire face of the tire. If you wear in the center, you have too much pressure. If you wear on the edges you have too little. It is best to have more than too little. More is better in that you will have less flex (harsher ride) but a reduce tire temperature. This is good to reduce the change of a blow out. So, my suggestion would be to start a little higher pressure that you think you need and adjust downward. This gives you more margin for safety.

 

[lizzyhermit]

Originally posted by Dieselnerd

Here's a chart that I copied from the TDR website quite some time ago.

then what do I do when fully loaded with 30' of TT and the truck axles weigh 3680# rear and 3880# front? The tire dealer recommends inflation per the door jam plate regardless of weight being carried. Is this good, bad or what?

 

[fest3er]

Originally posted by lizzyhermit


then what do I do when fully loaded with 30' of TT and the truck axles weigh 3680# rear and 3880# front? The tire dealer recommends inflation per the door jam plate regardless of weight being carried. Is this good, bad or what?

It is bad. With the rear tires so greatly overinflated, you only have 3-5 inches of rubber really contacting the ground. In a hard swerve or panic stop, the rear tires won't add much to the braking effort. The front tires aren't so bad, but you will also have less contact there, as well.

It is a real safety issue. Read the "Tire Information" booklet that came with the truck (if you didn't get one, go to your dealer and request one). That will tell you, for the tire size, what your pressures should be, empty and loaded.

Granted, it may be a pain to have to pump up the tires every time you haul something, then let them down when you are done. But *I* think the safety issue outweighs the inconvenience.

Fest3er

 

[Bhale]

I run my rears at 80 and front at 65. If i'm doing a long haul with the camper, boat and family at highway speeds i'll bump the rears up to 82 COLD and fronts up to 70. ALWAYS check tire pressure when the tires are cold, never hot. I also feel each tire when traveling to see if any one is running hotter than the one on the other side of the truck.



Example: This past week i went down to the outer banks for a few days with camper and family (~10,500lbs total weight). Stopped after about 3 hours of driving and did my walkaround. Found the right rear was WAY hotter than the left. Tire pressure was the same before i left so i kew that wasn't the problem but double checked anyway. These tires were brand new, got them put on 2 days before the trip. I couldn't figure out what was causing the heat so i increased the air pressure in the right side AirLift airbag to shift a bit more weight onto the left tire and kept my speed to about 55 mph. Found a tire shop down there and talked to the guys about my heat and they said the tire wasn't balanced correctly. They checked them and sure enough, i had lost 2oz off that tire! they rebalanced all 4 tires and on the ride home all was normal.



I'm sharing this with you because i feel it's important to check and double check things when your traveling and have so much loose for something so simple. Check regularly and you'll able to spot minor problems befor they become big ones. Thus endth the sermon.



BTW, i run Michlen LTX A/T's 245/75 R16.



Brian

 

[baby.driver]

Interesting Subject

I just put on new 285x75x16 rubber on 6. 5 in. wheels and had to lower the rears down to 26 lbs. before I could get a nearly even strike across the face of the tire. This is empty weight.

Maximum pressures are for maximum loads.



Jay

 

[dan_gilson]

baby. driver: Becareful about not going too low. At that pressure I would check the side wall for too much heat. When I dropped my duals down to 30PSI, they did heat up but just to the point of the fronts. The thing that I really noticed was the back end would squirm. This was because the side walls had a little too much flex. So I had to compromise: I pushed the pressure back up to 40PSI and lived with a little more tire wear. The other problem with too little pressure is that if you push hard into a corner you are more likely to roll the tire off the rim. That would be really bad.



The other option when increasing the pressure is to add more weight to the bed. It will ride smoother.

 

[Steve M]

I run 70psi front and rear towing and empty. Wear is even with the Michelins as they hold their profile when they're pumped up tight. Some other tires don't. I get better mileage with them at 70psi. And it rides like a truck!

Be careful running them too soft. They'll heat up and the first time you have to swerve hard they'll roll up under the rim and you'll have a wild ride.

 

[Hohn]

more tire pressure

Well, I weighed my truck on a CAT scale, and with a full tank, I have 4140# on the front axle, and 2700# on the rear. Based on the chart, I should only be running 48 PSI up front, and even less in the rear.

How far down should I go out back before things get too soft? I am thinking that 40-44 is where I want to be, because pressure is logarithmic, and load bearing tapers off fast as you get into the really low pressures.



Whadaya think?

 

[DHess]

55 psi in both front and rear and 70 in the spare since I'm empty most of the time. Makes it easier when I rotate every other oil change - about 5k miles. Will jack up the rear depending on the load. Michelins are wearing very well at 51,000 miles.



Dave

 

[baby.driver]

At this point it is experimental with me as these tires are so much taller and wider than the stock.

At 26#s on the rear there is only the smallest sag where the tire meets the road. About the same amount ALL radials used to have before the veh. manufacturers went to wider wheels.

When I had new 235/85 tires on at 50#s (rear) towing our fifth wheel, 600#s tongue weight and assorted other weight, so maybe 1000 to 1200#s total weight in the bed, on a 5000 mile trip the center 4 inches or so of the tread was worn nearly 50%.

With that size, 44#s is about as high as I could go with that load and not tear up the center of the tires.

Something to bear in mind is bigger tires with their increased internal square inches will hold up the same weight with less pressure.

Good exercise for the brain in any event.



Jay

 

[benhall]

Another good place to check air pressures is in your owners manual. Dodge has done the homework for us already and I found that they are very good numbers to go off of. For our 4x4's, they say 45 psi I believe. I put an extra 5 in all the way around for a little stiffer ride. Do what ever floats your boat.

 

[Sky]

I have kept mine at 45psi all the way around with towing about 5k never had a problem yet with 75k miles on the truck

 

[rakm]

Is that 75k on the same set of tires. If so that seems like a good pressure to go with.

 

[Tulsa618]

I’ve run about 58/48 front back for about 40K of running empty. I recently invested a whole $2. 95 in a tread depth gauge and found a consistent (all four) 9/32 middle, 6/32 inboard and 7/32 outboard on OEM 265/75E Michelins (rotation at 6K). With a slight under-inflation indication, I’ve kicked ‘er up to 68/58 front/back and will keep an eye on ‘em. I was hoping the gauge would be something I could use to inform my wife about how badly I need new tires , but coming down from a new depth of 14/32 (as measured on my “untouched” spare), my argument seems to have gone out the window – or perhaps, down the road… Might some of you tire gurus be able to provide a compelling argument that I could present The Boss with? Is the 6/32 inboard now “dangerous” – especially with winter coming on?

 

[George O]

I run 42 Rear and 52 Front unloaded and

52 Rear and 60 Front loaded.



Just turned 90K on the orig set of tires. Looks like

I may get another 4 or 5K of them which wont be to long.



Rotate every 6 or 7K.