China Bombs Got Me
I have read many posts about the poor quality of tires RV manufacturers are putting on new RV's. Well these tires (the infamous Tow Max Power King) blew on my 5er causing damage. I always check for p...
Forum Discussion
JJBirish,
There are a number of items in your post I would like to comment on, but in the interest of brevity, I’ll only focus on only one – one that I think is the key difference in our understanding of the DOT testing requirements. Perhaps we can find common ground.
First, I hope it is clear that tire “size” plays a large role in the rated load of a tire regardless of tire type. Put another way, larger tires have more rated load than smaller tires – all other things being equal. In trying to compare rated loads of tires of different types, we need to also compare tires of the same “size”. I put the word “size” in quotes because the letters in front of the numbers (in my view) also are part of the “size” as they delineate the type of tire involved.
When it comes to comparing LT tires and ST tires, there is a problem – very little commonality in “size”. I’m going to chose a “size” that is common to both LT’s and ST’s – 235/85R16 Load Range E:
ST235/85R16 LR E: Max Load 3640# at 80 psi – with a speed restriction of 65 psi.
LT 235/85R16 LR E: Max Load 3042# at 80 psi – and a common speed rating is Q = 99 mph.
Notice the difference in rated loads and speed restrictions. I hope it is obvious that a tire’s speed capability is inversely related to its speed – that is, the higher the speed, the less load it is capable of carrying (all other things being equal) – and that is reflected above.
So let’s take one of the DOT required LT tests and see how that plays out as far as load goes. How about this one:
For an LT235/85R16 Load Range E, the last step is 3042# load.
But for an ST235/85R16 Load Range E, that’s only 84% of its rated load. Or put another way, it is only 110% of the maximum load at 50 psi.
I think an ST tire can survive that last step.
Comments?
There are a number of items in your post I would like to comment on, but in the interest of brevity, I’ll only focus on only one – one that I think is the key difference in our understanding of the DOT testing requirements. Perhaps we can find common ground.
First, I hope it is clear that tire “size” plays a large role in the rated load of a tire regardless of tire type. Put another way, larger tires have more rated load than smaller tires – all other things being equal. In trying to compare rated loads of tires of different types, we need to also compare tires of the same “size”. I put the word “size” in quotes because the letters in front of the numbers (in my view) also are part of the “size” as they delineate the type of tire involved.
When it comes to comparing LT tires and ST tires, there is a problem – very little commonality in “size”. I’m going to chose a “size” that is common to both LT’s and ST’s – 235/85R16 Load Range E:
ST235/85R16 LR E: Max Load 3640# at 80 psi – with a speed restriction of 65 psi.
LT 235/85R16 LR E: Max Load 3042# at 80 psi – and a common speed rating is Q = 99 mph.
Notice the difference in rated loads and speed restrictions. I hope it is obvious that a tire’s speed capability is inversely related to its speed – that is, the higher the speed, the less load it is capable of carrying (all other things being equal) – and that is reflected above.
So let’s take one of the DOT required LT tests and see how that plays out as far as load goes. How about this one:
JJBIRISH wrote:
.....=================================================
Category B Endurance Test:
(LT "E" tire at 50 PSI)
4-hour test: 85% of tire maximum load rating at 75 MPH
6-hour test: 90% of tire maximum load rating at 75 MPH
24-hour test: 100% of tire maximum load rating at 75 MPH
……..
For an LT235/85R16 Load Range E, the last step is 3042# load.
But for an ST235/85R16 Load Range E, that’s only 84% of its rated load. Or put another way, it is only 110% of the maximum load at 50 psi.
I think an ST tire can survive that last step.
Comments?
