Originally Posted by jj2spirit
Thanks for the info...so if you were buying tires for your FF , you would buy the higher rated Khumo 's if I'm reading you right.
No that's not what I'm saying at all. I said to do the math and see if the stock tires are overloaded or compromised at all. Our Cobblestone (single axle) was compromised so that's why I bought the higher rated Khumos.
Using the formula I stated above, the fully loaded Cobblestone starts out at 3,500 lbs. I subtract the tongue weight with the WD hitch (-15%) = 2,975 + 20% safety margin = 3,570 lbs. The total capacity of the two tires were 3,520 lbs so I wasn't comfortable with the stock tires, that's why I chose the Khumos. Keep in mind, that they are not cheap. It cost $575 to have 3 of them mounted (2 per axle + 1 spare). Now if money was no object I'd gladly buy the Khumos, but then again, if money was no object, I wouldn't have a Fun Finder either
Our new Fun Finder is well below the load ratings on the stock tires so I don't see an issue with them. As I said, they worked very well and had no issues.
The fully loaded FF starts out at 6,000 lbs. I subtract the tongue weight with the WD hitch (-15%) = 5,100 + 20% safety margin = 6,120 lbs. The total capacity of the 4 tires are 7,040 lbs so I'm comfortable with that.
The leading cause of tire failure is heat - usually caused by under-inflation. This allows more flexing in the sidewall which generates more heat. This condition is made worse when traveling at higher speeds or on extremely hot days. Every time we stop I get out and put my hand palm down on the sidewall of each tire. In cold weather, they will be almost cool to the touch. In hot weather, they will be warm but not so hot that you can't keep your hand on them. (I do the same for the wheels separately). As LJAZ stated, the ST tires do have stiffer sidewalls which help minimize sidewall flexing. They also have chemical constituants in the rubber compound to resist UV degradation and cracking due to prolonged storage conditions that LT tires do not.