Goodyear Product Service Bulletin

[Roger M]

Researching the specifications of the Bigfoot tires I ran across the attached Goodyear Service Bulletin with helpful information regarding maximum speed and tire inflation pressure. The second bullet is of particular interest.

Quoting in part:

"Subject: Tires for Trailer Use Only: General Information (replaces PSB 2006-06)
This bulletin provides important information to help your customers obtain the best performance from “Special Trailer” tires. Please review the following important points with your trailer tire customers.
Special Trailer (“ST”) Tires
Goodyear Marathon trailer tires are widely used in a variety of towable trailer applications and are designed and branded as “ST” (Special Trailer) tires.
• Industry standards dictate that tires with the ST designation are speed rated at 65 MPH (104 km/h) under normal inflation and load conditions.
• Based on these industry standards, if tires with the ST designation are used at speeds between 66 and 75 mph (106 km/h and 121 km/h), it is necessary to increase the cold inflation pressure by 10 psi (69 kPa) above the recommended pressure for the rated maximum load.
o Increasing the inflation pressure by 10 psi (69 kPa) does not provide any additional load
carrying capacity.
o Do not exceed the maximum pressure for the wheel.
o If the maximum pressure for the wheel prohibits the increase of air pressure, then the
maximum speed must be restricted to 65 mph (104 km/h).
o The cold inflation pressure must not exceed 10 psi (69 kPa) beyond the inflation specified
for the maximum load of the tire."

[floyd]

Originally Posted by Roger M

Researching the specifications of the Bigfoot tires I ran across the attached Goodyear Service Bulletin with helpful information regarding maximum speed and tire inflation pressure. The second bullet is of particular interest.

Quoting in part:

"Subject: Tires for Trailer Use Only: General Information (replaces PSB 2006-06)
This bulletin provides important information to help your customers obtain the best performance from “Special Trailer” tires. Please review the following important points with your trailer tire customers.
Special Trailer (“ST”) Tires
Goodyear Marathon trailer tires are widely used in a variety of towable trailer applications and are designed and branded as “ST” (Special Trailer) tires.
• Industry standards dictate that tires with the ST designation are speed rated at 65 MPH (104 km/h) under normal inflation and load conditions.
• Based on these industry standards, if tires with the ST designation are used at speeds between 66 and 75 mph (106 km/h and 121 km/h), it is necessary to increase the cold inflation pressure by 10 psi (69 kPa) above the recommended pressure for the rated maximum load.
o Increasing the inflation pressure by 10 psi (69 kPa) does not provide any additional load
carrying capacity.
o Do not exceed the maximum pressure for the wheel.
o If the maximum pressure for the wheel prohibits the increase of air pressure, then the
maximum speed must be restricted to 65 mph (104 km/h).
o The cold inflation pressure must not exceed 10 psi (69 kPa) beyond the inflation specified
for the maximum load of the tire."

Thanks for finding that and posting it. I had found it some time ago. When I wanted to refer to it I could not find it again, even after exhaustive searching. It will definitely be given a bookmark.

[Roger M]

You're welcome Floyd and props to Tire Rack for supplying the bulletin and a wealth of other information on tires etc.

As a RV rookie, inflating a tire over the max psi stamped on the tire was news to me and brings a welcome new level of confidence at those times when I find myself approaching 75mph. 65mph is my target speed but my truck has a sweet spot around 72, so throttling down en route is much more common towing the trailer.

Roger

[Byron Kinnaman]

Originally Posted by Roger M

You're welcome Floyd and props to Tire Rack for supplying the bulletin and a wealth of other information on tires etc.

As a RV rookie, inflating a tire over the max psi stamped on the tire was news to me and brings a welcome new level of confidence at those times when I find myself approaching 75mph. 65mph is my target speed but my truck has a sweet spot around 72, so throttling down en route is much more common towing the trailer.

Roger

However one must remember that in some states there is a towing speed limit. California is one, Oregon is another. Both have maximum towing speed of 55 mph. California is usually well posted, Oregon isn't.

[GeorgeR]

Originally Posted by Roger M

You're welcome Floyd and props to Tire Rack for supplying the bulletin and a wealth of other information on tires etc.

As a RV rookie, inflating a tire over the max psi stamped on the tire was news to me and brings a welcome new level of confidence at those times when I find myself approaching 75mph. 65mph is my target speed but my truck has a sweet spot around 72, so throttling down en route is much more common towing the trailer.

Roger

I didn’t conclude from this bulletin that you can exceed maximum inflation pressure, the one stamped on the tire; what I read was that you can exceed the cold inflation pressure by 10 psi above the recommended pressure for the rated maximum load up to maximum pressure. So, whatever is on stamped on the tire is your maximum pressure. If your maximum load pressure is 45PSI you can increase it to 55PSI if 55PSI is your maximum tire inflation pressure, the one stamped on the tire.

George.

See page #9 for inflation table to clarify above statement:
http://www.goodyearrvtires.com/pdfs/tire-care-guide.pdf

[Roger M]

It seems there is a question over the "recommended pressure for the rated maximum load" since Goodyear does not give a number for that term in the TSB. However on page 9 of the Tire Care Guide the "recommended pressure for the rated maximum load" for a ST225/75R15 load range D is 65psi at 2540lbs. At 45psi the max load is 2020lbs, and at 70psi and higher the max load remains 2540lbs.

Given that a the ST225/75R15 is also a "R" rated tire at 106mph, the TSB seems clear that an increase of 10mph over the, again "recommended pressure for the rated maximum load" is indeed 65psi. The last bullet "The cold inflation pressure must not exceed 10 psi (69 kPa) beyond the inflation specified for the maximum load of the tire." should confirm the said tire max numbers are75psi at 75mph carrying 2540lbs.

Personally this just gives me peace of mind when I catch myself creeping over my target speed. If there are any errors in these figures please let me know.

[GeorgeR]

Based on this, above stated,comment and PM I received I would like to correct my previous post. I am running my tires at 40PSI with maximum inflation of 50PSI which prompted me to think that that I indeed have 10PSI budget to go for a higher speed.
In quick reading the statement of not to exceed maximum wheel pressure was another monkey wrench into my thinking; a maximum wheel pressure is not maximum tire pressure.
Thank you all for your input, George.

[Roger M]

Hey George, without your upload of the Goodyear Tire Care Guide and the tire pressure chart we never would have figured out what "recommended pressure for the rated maximum load" means exactly. I've read on several forum posts of quality tires like Goodyear, Kuhmo and Maxxis suffering premature blowouts and wonder if under-inflation could be the cause.

My next step is a trip to the truck scales to see exactly how much weight I'm pulling back there.

Thanks for your contribution. Roger

Correction: In a previous post the "R" in ST225/R15 indicates Radial, not a speed rating of 106mph. Those darn monkeys with wrenches.