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Old 09-04-2013, 12:22 PM   #21
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Originally Posted by Tireman9 View Post
Cascade Bob
Thanks for the info. One question. Are your tires ST or LT?
Hint: When writing a tire size it helps if the letters in front of the numbers are included. It also helps if you include the "Load Range" letter. C, D, E, F etc.
Tireman9

My tires are ST 235/80/16
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Old 09-05-2013, 02:56 PM   #22
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I filled in the weights of cascade bob in to my motorhome-tire-pressure calculator part 3 , though I know its a travel trailer, 5th wheeler or whatever thing to tow . But stopped when filling in the loads when I saw the rear left of 2800 lbs . Is that realy so or a miswriting?

If realy so it shows that for tandem axle it yust the same as for motorhomes , that you can have crossed weight differences .
Mostly that is courced by something heavy ( or more things) on that left rear behind the axle. this lifts up the front axle on that same side.

Best would be then to try to shift some heavy load to front right if possible, for more even loading over the 4 wheels.
But otherwise base the pressure on the heavyest tire so here RL of 2800 lbs.
Hoping the tire is allowed to bare that load.

You stil did not give the loadrange ( D to H letter) so we cant determine the maximum load of this tire.

This PDF of Goodyear shows at botom of page 1 that you may overpressurise the AT pressure by 10 psi.
http://www.goodyeartrucktires.com/pd...dinflation.pdf
It writes
B.When higher pressures are desirable to obtain improved operating performance.
The combined increases of A and B should not exceed 10 PSI above the inflation specified for the maximum load of the tire
wich is that 80 psi for instance for a E load tire. So its allowed to use 90 psi for such a tire.

My idea is that for that 2800 lbs LR you will come higher then the AT-pressure for your tires.
Best is to see if you can find a LT tire with same sises and AT-pressure,and use the maximum load of that tire in my calculator .
Then if the outcome is AT-pressure +10 psi , use that to be absolutely save.

But this case shows why ST tires are adviced at their maximum, because one tire often comes to high loads
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Old 09-05-2013, 03:12 PM   #23
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Load range E, Max load 3500 pounds at 80 PSI
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Old 09-05-2013, 10:20 PM   #24
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Originally Posted by jadatis View Post
snip


This PDF of Goodyear shows at botom of page 1 that you may overpressurise the AT pressure by 10 psi.
http://www.goodyeartrucktires.com/pd...dinflation.pdf
It writes
B.When higher pressures are desirable to obtain improved operating performance.
The combined increases of A and B should not exceed 10 PSI above the inflation specified for the maximum load of the tire
wich is that 80 psi for instance for a E load tire. So its allowed to use 90 psi for such a tire.

snip
Sorry jadatis you apparently did not read the information on pg 2 Table 1
"For LT Tire Sizes Only (e.g., LT235/85R16, LT245/75R16). For Truck and Bus Sizes (e.g., 225/70R19.5, 245/70R19.5), use Table 2 below."

Bob's tires are ST type so this Goodyear document does not apply. Your suggestion that it is OK to use 90 could be dangerous. Do you have liability insurance?
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Old 09-06-2013, 06:23 AM   #25
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Here's an idea.....inflate tires to prescribed pressure per each tire, and keep road speed at or under 65mph (NO ONE needs to rip down the road pulling a 15k trailer over that), and you will be fine. Assuming of coarse the tires are road worthy. And for the one's who ask why their busting beads or worrying about breaking belts because they 'spin' their trailers around on a dime...simple, don't get yourself in those tight areas. Focus on what your next move will be, before you get there.
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Old 09-06-2013, 11:34 AM   #26
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Don't forget the 65mph on the ST tires is like the Red Line on your engine.
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Old 09-06-2013, 11:59 AM   #27
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Here's an idea.....inflate tires to prescribed pressure per each tire, and keep road speed at or under 65mph (NO ONE needs to rip down the road pulling a 15k trailer over that), and you will be fine. Assuming of coarse the tires are road worthy. And for the one's who ask why their busting beads or worrying about breaking belts because they 'spin' their trailers around on a dime...simple, don't get yourself in those tight areas. Focus on what your next move will be, before you get there.
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Old 09-06-2013, 02:10 PM   #28
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Originally Posted by Tireman9 View Post
Sorry jadatis you apparently did not read the information on pg 2 Table 1
"For LT Tire Sizes Only (e.g., LT235/85R16, LT245/75R16). For Truck and Bus Sizes (e.g., 225/70R19.5, 245/70R19.5), use Table 2 below."

Bob's tires are ST type so this Goodyear document does not apply. Your suggestion that it is OK to use 90 could be dangerous. Do you have liability insurance?
Tire rack says it too for ST tires .
Then used for higher speed, but indicates that they allow 10 psi higher.
dustry standards dictate tires with the ST designation are speed rated to 65 MPH (104 km/h) under normal inflation and load conditions.

However industry standards also stipulate, if tires with the ST designation are used at speeds between 66 and 75 mph (106 and 121 km/h), it is necessary to increase their cold inflation pressure by 10 psi (69 kPa) above the recommended pressure for the rated maximum load.

Do not exceed the wheelís maximum rated pressure. If the maximum pressure for the wheel prohibits the increase of air pressure, then maximum speed must be restricted to 65 mph (104 km/h).

The cold inflation pressure must not exceed 10 psi (69 kPa) beyond the inflation specified for the maximum load of the tire.

Increasing the inflation pressure by 10 psi (69 kPa) does not provide any additional load carrying capacity.
herehttp://www.tirerack.com/tires/tirete...jsp?techid=219
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Old 09-06-2013, 02:23 PM   #29
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Load range E, Max load 3500 pounds at 80 PSI
Then for your 2800 lbs on the heaviŽst tire LR you have to use that 80 psi.
And because rule is all tires same pressure all 80 psi wich will give bumping because of the lightest tire.

Your tire 3500 lbs max load /1,15 ( I calculated once that a ST has 15% more maximum load) * 0,925 ( wich is for dual load , I now use for tandem axle for all savety) gives maximum load a LT tire would have for dual load 2815 lbs AT 80 psi. so I did not have to calculate because thats about the same as your load .
So you dont need the extra 10 psi , unless it was weighed empty.

If you are able to shift some load, so the heaviŽst tire gets lower then that 2800 lbs ( is it realy that high???) then you can savely go lower, even going from 2815 max load for lesser saver deflection.
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Old 09-06-2013, 03:56 PM   #30
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I'm lost here. I originally responded to Smokin because he has the same camper and optional wheel/tire combination as I have. He asked what tire pressure he should run on his camper. I responded that I run 80 PSI, the maximum recommended cold inflation pressure. I included the actual individual wheel position weight of each of my loaded camper tires. All are well within the maximum load of 3500# per tire for my ST tires. The camper tows flawlessly with 80 PSI... no bounce, no wander or other problems. I tow at 65mph or less (the max speed rating of ST tires). The discussion of adding 10 PSI to increase tow speed for ST tires seems foolish, stick to the manufacture's recommendations or buy LT tires and stay within the speed rating and tire load limits if you want to drive 75. I've owned pop ups, TT's, motor homes, and 5th wheels over the last thirty years without a tire failure. As 5erdriver and Tireman9 recommend, I'll continue to stick with the manufacturer's recommendations and hope my luck holds.
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