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I had a friend tell me to be sure and keep the same air pressure in all 4 tires the same all around. I had told him I ran 5 more pounds in the front tires. He said that since my truck was a 4X4 the tire circumference would be off a little with different air pressure and that this was hard on the transfer case. Anyone ever heard of this?????? Can 5 pounds make a real difference?????
 

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You are correct.Unless towing to capacity,I've always run a little less in the rear.Front is alot heavier when empty.Rides better too.Tell him that if that was the case,you'd have to run less in the back anyways so the tires bulge out the same!
 

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Steel belted radials do not grow appreciably with air pressure. Their rollout is about the same regardless.

I usually run more air in the fronts.
 

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I don't believe it. The door sticker says something like:
65PSI front
80PSI rear

I know the 80 in the rear tires is only for towing, but I run about 55 all around when not towing.
 

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cwq21;1575379; said:
I don't believe it. The door sticker says something like:
65PSI front
80PSI rear

I know the 80 in the rear tires is only for towing, but I run about 55 all around when not towing.
load range d tires should be kept the same or close at least the load range e are diffrent pressures. more pressure does make the sidewall taller and stiffer but you truck isnt going to notice any diffrence.
 

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oh yeah and your circumfrence will change on a tire that is low thats how some of the earlier tire pressure monitoring systems work they use abs wheel speeds to figure out a tire is down. the newer ones use sensors in each wheel. 5 psi wont make a diffrence 15 will
 

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In order for THE TIRE FOOT PRINT to be the same on the front and rear tires on the Dmax, the tire presure HAS to be different, thus maintaning the same rotating distance on the front and rear tires.

drive safe
 

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So if i run 55lbs in the front and put 45 in the back they will be okay untill i pull my trailer then up the rear tires.
 

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maxy;1576514; said:
So if i run 55lbs in the front and put 45 in the back they will be okay untill i pull my trailer then up the rear tires.
You'll be fine.

If our vehicles had a 50%Front/50%Rear weight distribution then I'd say, yeah, run all the tires the same pressure. But the diesel (and even the 8.1L) is awfully heavy and if you have the same air pressure in all four tires, the rolling diameter (easily measured) of the front tires will be smaller than the rear, and that my friend will be hard on the drivetrain on less than slippery surfaces.

DEWFPO
 

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maxy;1576514; said:
So if i run 55lbs in the front and put 45 in the back they will be okay untill i pull my trailer then up the rear tires.
Exactly correct. I run that combination and air up the rears when pulling or loaded accordingly. On a side note, if you do run the fronts too low (GM used to recommend 45 psi for "ride quality") it will EAT THEM UP in no time, cupped, bald on one side, about 1/3 of the normal wear life - I found out the hard way on my first set of tires because the dealer set them that way and I didn't know better!
 

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i cant see it being "hard" on the t-case UNLESS your driving around in four wheel drive all the time. and even then, i dont think 5#'s of air is gonna be that big of a deal.
 

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With tire pressure the tire's will pay the price before the transfer case, transmission or any part of the drive line will. Keep an eye on your tire wear if it changes you should adjust your pressure accordingly.
 

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myojunk;1576919; said:
i cant see it being "hard" on the t-case UNLESS your driving around in four wheel drive all the time. and even then, i dont think 5#'s of air is gonna be that big of a deal.
In this scenario, the difference in rolling diameters is cumulative as the tires cover more ground. That difference has to be 'released'. This is typically done by the tires as they travel over 'lower traction' surfaces. You have one axle turning different rpm's than the other, but it's not a problem because the tires will slip and release the binding. If your not on a 'lower traction' surface, it puts stress on the transfer case, u-joints, driveshafts, cv joints, etc.... until the binding overcomes the tire's traction and a tire slips, or a part breaks. We all hope that the parts in our HD's are stout enough to cause the tires to take the brunt of the punishment.

If the rolling diameters are identical, then theoretically you could drive in 4wd in a straight line forever on a asphalt or concrete surface and not have any problems or added stress.....until you turn.

DEWFPO
 

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Ya, what Idle Chatter and letsgo said.
The front axles weight is about 4100 lbs, and the rear is about 3100 lbs.
55 PSI in front and 45 PSI in rear, (when unloaded), will give similar tire patch contact, and now if you measure center of axle to ground on each axle, they should be similar, giving you equal rolling radious'.
If you load more weight, adjust pressure accordingly. If you're using 4WD on slippery surfaces like you're supposed too, the wheels will slip if rotating at different RPMS.
 

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Just trying to explain his friends in-accurate thinking for our trucks.
Sorry if it offended you. Never said I was afraid of anything.
 

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All of my lessons in Geometry tell me that the circumfrence of a tire cannot change because of tire pressure. The ammount of total surface area doesn't change only the amount of surface in contact with the road and the drag coefficient it has. This will definately affect ride quality and tire wear but not the driveline dynamics.
 

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crash457;1580122; said:
All of my lessons in Geometry tell me that the circumfrence of a tire cannot change because of tire pressure. The ammount of total surface area doesn't change only the amount of surface in contact with the road and the drag coefficient it has. This will definately affect ride quality and tire wear but not the driveline dynamics.
As more weight is put on a tire, the tire compresses, reducing the rolling diameter. The added weight can be compensated by adding air pressure (to a degree).

When you have a tire that has low air pressure in it, the vehicle sits lower than normal because the rolling diameter has changed, you add air and the vehicle rises.

DEWFPO
 

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DEWFPO;1580374; said:
As more weight is put on a tire, the tire compresses, reducing the rolling diameter. The added weight can be compensated by adding air pressure (to a degree).

When you have a tire that has low air pressure in it, the vehicle sits lower than normal because the rolling diameter has changed, you add air and the vehicle rises.

DEWFPO
I agree that the Diameter changes but the circumfrence doesn't so the distance traveled for on revolution is the same. What can advresely affect driveline components is when two tires on the same driveline (be it the same axle or through a transfer case) travel at different speeds. This would only happen when the circumfrence of the tires is different.
 

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The circumference does change because the diameter changes.

DEWFPO
 
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