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Old 03-15-2019, 04:38 PM   #1
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TowMax STR II Tire Pressure above maximum sidewall

Has anyone read this before, or done it? Results?



From TireRack.com:

Special Trailer (ST) Tire Speed Ratings

Unless assigned a specific Speed Rating, industry standards dictate tires with the ST designation are speed rated to 65 mph (104 km/h) under normal inflation and load conditions.
However, Goodyear Marathon and Power King Towmax STR tires featuring the ST size designation may be used at speeds between 66 and 75 mph (106 and 121 km/h) by increasing their cold inflation pressure by 10 psi (69 kPa) above the recommended pressure for the rated maximum load.
Do not exceed the wheel's 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.




Link to the TireRack Page




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Old 03-15-2019, 07:39 PM   #2
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Yes

Note that it is 10 psi above the psi called out in the tires chart for the actual weight on the tire NOT TO EXCEED the pressure printed on the side wall.
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Old 03-16-2019, 03:08 AM   #3
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Yep, saw that. No increase in weight rating, only speed. "L" speed rating, up to 75mph.
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Old 03-20-2019, 03:47 PM   #4
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I think you'll find a statement in just about all RV trailer owner manuals will prohibit that action without express approval from the vehicle manufacturer.

This is how it's written in the 2019 generic Keystone trailer manual.

"Because tires are designed to be used on more than one type of vehicle, tire manufacturers list the “maximum permissible inflation pressure” on the tire sidewall. This number is the greatest amount of air pressure that should ever be put in the tire under normal driving conditions."
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Old 03-20-2019, 04:03 PM   #5
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Quote:
Originally Posted by BriaBeck View Post
Has anyone read this before, or done it? Results?



From TireRack.com:

Special Trailer (ST) Tire Speed Ratings

Unless assigned a specific Speed Rating, industry standards dictate tires with the ST designation are speed rated to 65 mph (104 km/h) under normal inflation and load conditions.
However, Goodyear Marathon and Power King Towmax STR tires featuring the ST size designation may be used at speeds between 66 and 75 mph (106 and 121 km/h) by increasing their cold inflation pressure by 10 psi (69 kPa) above the recommended pressure for the rated maximum load.
Do not exceed the wheel's 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.




Link to the TireRack Page




.
I would NEVER go over the max pressure posted on the TIRE itself. I think (my opinion only) that would be disasterous. Do the speed its rated for.
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Old 03-20-2019, 04:14 PM   #6
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there are st tires rated to 80+ i believe the new goodyear endurance . also the Carilse are rated to 81 . i always run max cold psi .
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Old 03-20-2019, 06:05 PM   #7
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I think there has been a misunderstanding about the 10PSI business.

In no case can you inflate above the sidewall pressure.

If you need the sidewall pressure to support the loaded weight, you may NOT add the 10PSI and you are limited to the 65 MPH rating of a standard ST tire.
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Old 03-20-2019, 06:07 PM   #8
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Originally Posted by MR.M View Post
there are st tires rated to 80+ i believe the new goodyear endurance . also the Carilse are rated to 81 . i always run max cold psi .
Only load range E tires are rated to 80 PSI
Load range D tires are rated to 65 PSI
Load Range C tires are rated to 50 PSI

You are conflating the manufacturer with the load range.
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Old 03-20-2019, 10:07 PM   #9
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Quote:
Originally Posted by Herk7769 View Post
Yes

Note that it is 10 psi above the psi called out in the tires chart for the actual weight on the tire NOT TO EXCEED the pressure printed on the side wall.



Herk,


I just re-read your post... and that is NOT what the TireRack.com page says.


It says you may not exceed the wheel's maximum pressure rating... not the tire.
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Old 03-20-2019, 10:21 PM   #10
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If your RV placard inflation is already equal to the maximum tire pressure stamped on the tire you will not have that option. Otherwise I would follow the tire manufacture recommendation. In my case my RV placard is 123 PSI and my sidewall maximum tire pressure is 123 PSI so I cannot increase pressure at all. 62 mph is my max speed. I have learned how to slow down and enjoy the ride.
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