FastEagle wrote:
.....Its very interesting that you should mention tire sidewall flex location. I’ve always believed that the ST tires flex location may be situated where it will be beneficial to the scrubbing action of dual - or more - axle dragging during sharp turning actions. Because I’ve never run across a reference describing such actions in the ST tire I’ve always been reluctant to bring it up.
Here is a quote from the Carlisle Tire Company about their ST tires: “Generally, the ST tire also has somewhat stiffer sidewalls, especially in its lower section. This reduces sidewall flexing, helping it to track straighter and diminish the risk of trailer sway. The stiffer sides also lessen the risk of sidewall blowout.”
Can you give us a technical response to that?
FastEagle
I know you addressed this to Roger, but allow me to take a shot at it.
First, Yes, ST tires are built stronger than Passenger Car tires. They have to be as they use more inflation pressure.
This quote: "....stiffer sidewalls, especially in its lower section. ..." is especially misleading as you can say that about EVERY tire. The term is "turn-up" and it describes the way the ply is tied into the bead by wraping a flap of fabric around the bead bundle. Put another way, it's a partcularly useless and throwaway statement.
Once you understand that, then you realize the rest of the statement is also useless. If every tire has a stiffer lower sidewall, then every tire would reduce sway (and they do!) - and all the rest of that - while ture - is not peculiar to ST tires.
And, FE, I think you mean to talk about tandem tires, not duals. Tandem's are in line with each other, while duals are on the same axle (and the same side).
I think you are making too much of the flexing that takes place in tires when maneuvering a tandam axle trailer. By and large that is done at slow speeds, and the only reason it is visible is because the 2 tires are forced to stay in that position by the tow vehicle. If you were to watch high speed video of a tire on a car when it is cornering, you would see the same sort of movement.
Watch this video to see what I mean. Watch how much movement there is in the sidewall:
Calspan Force and Moment Tire TestAnd on a personal note: I think people make way too much of the sidewall's affect on tire flexing and durability. Most of this type of thing is not a result of sidewall strength or stiffness.
And one last item- sidewall blowouts are virtually never the result of a defect. They are almost 100% caused by hazards of the road - punctures and impacts - and once you understand that, then it's easy to see why I made the statement in the previous paragraph.
