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Tire Sidewall Pressure Statement


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I have these Kelly drive tires, G rated. They have a statement on the side that says something to the effect - " For speeds above 60 MPH, add 10 psi with no increase in load capacity"


I don't need more load capacity with 26K on the rear, I have checked the rear tires with an IR thermometer and they run relatively cool just a few degrees above ambient without doing the 10 psi.


What's the deal with this add 10 psi thing?




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This is an older/less common way of dealing with Speed ratings. As Highway speeds have change over the years, the Commercial tire folks did retesting for speeds greater than 65 mph (usually) and have gone to more regularly adding the service description, which includes the speed rating.

Often there was not a Service description (with speed rating) and most commercial tires were rated at around 60-65 mph with this adjustment from Tire and Rim Association. (When Highway Speed limits were lower)


If it says 60 mph then this is the speed rating for this tire and should not be exceeded. Unless... one adds 10 more psi (above pressure for the load - as found on an inflation table) then one could increase the continuous speed rating of the tire to 70-75 mph. However, this would not increase the load carrying capacity of the tire.

There is a little more to it but this is the jest of the adjustment for this situation and type of tire.

For most new tires this is NO LONGER THE WAY IT IS NORMALLY DONE. Most Tires have been retested for the current general Highway speeds (75 mph) and given a speed rating which is found on the service description. Some may be lower than 75 mph and this should not be exceeded. (unless the manufacturer gives special instruction or a variance)


The service description is two three digit numbers (Load index for single/dual) followed by a letter (speed rating) example - 135/133J)

J-62 mph

K-68 mph




Most of the new Kelly tires for Long haul or region service are now given 75 mph speed rating.


How old are the tires?

What is the model of the tire? Check here for Kelly tire specs and to see speed ratings

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Trey - thanks for the info, sounds like tires are your forte.


These are Kelly KDA Armorsteel


DOT MJ37 BCKW 3710


So, manufactured week 37 of 2010 ?


The fronts are Goodyear G399 LHS. They were built 2511 and don't have the 10 psi statement on them.


All 295/75 R22.5.


My weights are 9700 on the front, and 26K on the rear, trailer on, Mini on, full fuel, all loaded for the road.


So are they tires junk? should I be springing for new Michelins before they take out by tool boxes? Fee free to lay some "truth" out there.


The tires were all "new" on the truck when I got it so they cheaped out as much as possible.


The truck is stored inside, so no sun on the tires. At what age should I be swapping these out? I will never wear them out but age will drive replacement.




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Hey Rich, I would trust Phil's experience with this tire.

It seems that the newer version of the KDA Armosteel is speed rated for 75 mph, since the specs on the Kelly site indicate this. I am not sure what manufacturing year this change took place for this tire.

It is good to know the speed rating because this will affect the lifespan of the tire and how you should maintain pressure for the way you drive as well as your safety.

Age is very dependent on how the tire is maintained, so if the tires are maintained properly, then they will last longer. Phil will have a better idea - knowing that he takes care of his equipment.

On a quick look, the Kelly warranty does not seem to cover tires purchased before January 2013, but on this document 4 years appears to be the limitation they allow for just about anything. This is a little less than the second or first tier tires (5-7 years - however some reduce the warranty time for non-commercial use like RV use). Unless Phil gives something different I would begin to be thinking about a strategy for tire replacement for these since the warranty has already passed. RV use is hard on tires for many different reasons which equates to a reduced life span. But the better care taken will definitely give give longer life, with proper inflation at the top of the maintenance list. If you have cared for them then maybe a while longer.


The Goodyear 399A is speed rated for 75 mph. This tire has a premium casing and basically the casing warranty is 7 years for this tire.


In general, after 5 years it is good to get the evaluated by a well trained truck tire shop manager. Then the risk begins based on the quality of the tire and the care given. The best Commercial Tires should not be used more that 10 years after manufacturer Date code.

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