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Old 06-29-2012, 11:53 AM   #11
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I agree, slightly over inflated (but not over tire's max) is better. My example was just to show the "why" of the "assumptions". In this case VRMHW-W will probably be close to the capacities of both tow vehicle and trailer, but that may not be always the case. A 350/3500 pulling a pop up or hybrid would not be anywhere near capacity or a fifth wheel with a 4000 cargo capacity that someone is just throwing in a "few things" for a local weekend trip might not be as well. I just remember things better if I understand the "why" part of them.

Without knowing for sure, that is why I suggested at the end to add 10 PSI to where you think you should be - better to be slightly over than under inflated.
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Old 06-29-2012, 11:59 AM   #12
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Of course another method is to draw a chalk line across the tread and drive a few revolutions and check. If the chalk wears off in the center of the tread first, the tire is over inflated and you need to let air out. If the chalk wears off on the outside first, the tire is under inflated and you need to add air. Once it wears off evenly, you are about right.

However you need to drive straight for this to be accurate, especially with trailer tires. When you turn, a trailer with tandem and triple axles drag the tires sideways and will remove the chalk and not give a correct interpretation.
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Old 06-29-2012, 12:08 PM   #13
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Originally Posted by herk7769 View Post
IMO, You are right, If you have no clue as to what "correct" is then slightly overinflated is "better" than slightly under inflated.

Slightly is the operative word since over hard tires can make for an unsafe ride as well.

When I forget to reset my truck's tires back to "normal-not towing" it is a skittish as a young girl.

I have nearly lost control on more than one occasion braking going down a hill. Trucks tear up the asphalt leaving "ripples" in the pavement at the stop sign at the bottom and when my tires are at 80PSI the truck dances all over the place. Set normally (65 PSI) they handle it just fine.
Exactly the point, after I unhitch the fifth wheel, if I don't air back down the tires on the Power Wagon, besides loosing a kidney from the ride, it is bouncing all over the place. Can't hardly control it much over 10 MPH on a washboard dirt road.

My employer provided work vehicle is a Ford F-150 that they have put LT load range E tires on. Every time it goes in for service they air the tires up to 80 PSI and I can't hardly keep it in a lane when I hit a bump or pot hole. Going over railroad tracks usually puts my head through the roof of the cab, so I air back down to a reasonable pressure until it goes back in for service and we start the process over.
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Old 06-29-2012, 12:46 PM   #14
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Originally Posted by Glenn5995 View Post
A 350/3500 pulling a pop up or hybrid would not be anywhere near capacity or a fifth wheel with a 4000 cargo capacity that someone is just throwing in a "few things" for a local weekend trip might not be as well.
Yeah, no kidding. If someone has a 350 pulling a pop up and is concerned with adjusting their pressures between towing/not towing they got too much time on their hands. you might as well winch it up into the bed. OK, OK, I know there's some big PUPs out there, but you know what I mean....

I also assume we're not dealing with the other extreme like a minivan or RAV4 pulling a 35 footer TT either
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Old 06-29-2012, 01:09 PM   #15
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In the case of the OP, although she will most likely be near rated capacity for a Tahoe's GVWR and GAWR, she said the max tire pressure is 80 PSI, so she must have LT load range E tires. They have more capacity than the axles or the projected load, so she will not need them at 80 PSI.
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Old 06-29-2012, 03:02 PM   #16
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OK... I guess I'm still learning as I didn't realize that tires should be inflated higher than what the TV door sticker recommends.

I have a F150 SCREW with Goodyear Wrangler SR-A tires (P275 65R18).

TOTAL RIG CAT WT.
Steer Axle: 3400 (w/ 2 passengers)
Drive Axle: 3260
TT Axle (2): 3660

CAT Wt of F150 alone w/ 1 passenger was 5900 lbs

Ford says 35lbs PSI and tire shows 44lbs PSI max. Goodyear max load chart says 2601@51. My unhitched TV by itself is 1475 lbs per tire so I'm OK on load. I called one dealer and inquired as to pressure when towing and he suggested 40 PSI which is an increase of 5 lbs PSI. Another dealer suggested 50 PSI which is an increase of 15 PSI vs. normal.

Which PSI sounds correct for towing?
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Old 06-29-2012, 04:14 PM   #17
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Quote:
Originally Posted by FreedomTracker View Post
OK... I guess I'm still learning as I didn't realize that tires should be inflated higher than what the TV door sticker recommends.
The door sticker has the recommended pressure for RIDE not necessarily load bearing. The tire pressure MAY need to be increased up to the maximum stated on the tire in order to carry the load required of them.
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Old 06-29-2012, 04:29 PM   #18
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Originally Posted by FreedomTracker View Post
OK... I guess I'm still learning as I didn't realize that tires should be inflated higher than what the TV door sticker recommends.

I have a F150 SCREW with Goodyear Wrangler SR-A tires (P275 65R18).

TOTAL RIG CAT WT.
Steer Axle: 3400 (w/ 2 passengers)
Drive Axle: 3260
TT Axle (2): 3660

CAT Wt of F150 alone w/ 1 passenger was 5900 lbs

Ford says 35lbs PSI and tire shows 44lbs PSI max. Goodyear max load chart says 2601@51. My unhitched TV by itself is 1475 lbs per tire so I'm OK on load. I called one dealer and inquired as to pressure when towing and he suggested 40 PSI which is an increase of 5 lbs PSI. Another dealer suggested 50 PSI which is an increase of 15 PSI vs. normal.

Which PSI sounds correct for towing?
Part of your problem is your tires. Your tires have a P rating which is a "SL" (or standard load) metric type SUV tire and not a true Light Truck "LT" tire.

Tire Tech Information - Load Range/Ply Rating Identification

Explains why you should consider replacing your OEM tires with true truck tires if you tow. Most F-150 trucks sold never see a trailer; ever.

http://www.tirerack.com/tires/tirete....jsp?techid=70

If you insist on keeping those tires and towing, I would increase the pressure to 44 PSI whenever I was going to tow.
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Old 06-29-2012, 04:35 PM   #19
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As long as you have the OEM tires, you should go by the door sticker for a guide. It is when you replace tires with other than OEM that it does not apply. At what weight is the 35 PSI recommendation? I doubt it is for the GVWR. It is most likely for an empty or light load.
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Old 06-29-2012, 04:54 PM   #20
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Originally Posted by Glenn5995 View Post
As long as you have the OEM tires, you should go by the door sticker for a guide. It is when you replace tires with other than OEM that it does not apply. At what weight is the 35 PSI recommendation? I doubt it is for the GVWR. It is most likely for an empty or light load.
Again it is for optimum ride and handling; not maximum load bearing.

http://www.4wheelparts.com/tire-whee...e-checker.aspx
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