QuestionQUESTION: If all radials have a network of bead-to-bead steel cords, why do sidewalls claim 1 or 2 "poly" plies?
Secondly, is it correct that a rated 8-ply's sidewall differs from a 4-ply's only be the size of the cords in their plies?
Finally, is there an approx. 3/4" band reinforcing the shoulder of "XL - extra load" tires with 102 load indexes?
ANSWER: Bill,
The polyester plies are what goes bead to bead, not the steel belts.
Secondly, the term ply can have 2 meaning relative to tires. "Ply" can refer to a layer of fabric - as in the answer to question #1. It can also mean an old term "Ply Rating" which has since been replaced by the terms "Standard Load (SL)", "Extra Load (XL)", for passenger car tires, and "Load Range (LR)" for everything else. These terms were invented to prevent confusion.
So allow me to rephrase your question using those terms: Is it correct that a Load Range D's sidewalls differs from a Load Range B's sidewalls only by the size of the cords in their plies?
Answer: May be. Certainly a LR D would have more overall material strength in the sidewall and there are 3 ways to achieve that: a larger cord, more plies of the same cord, a different but stronger cord material (say polyester to steel).
Finally, it is common for XL tires (of any load index) to have "cap strips" that cover the edge of the belts. This helps stabilize the belt edge and prevent growth due to centrifugal forces. However, this isn't 100% and some manufacturers use cap plies - which go across under the tread area and you will find listed on the sidewall under "tread" as a separate layer, such as: "Tread: 2 polyester + 2 Steel + 1 Nylon" - Nylon being a commonly used cap ply material.
---------- FOLLOW-UP ----------
QUESTION: Thank you, Barry, I may not be able to find a long-lasting tire for my 2002 Eurovan MV, but at least now I have some tools to sort through all the b.s. I think I will give up some sidewall stiffness and go with Michelin's HydroEdge (UTQG 800). VW spec'd a difficult-to-find 102 load index 225/60/16 tire for the entire line of Eurovans. Since our MV is 900 lbs. lighter than the camper, I have been running 97-98 load index tires until they are down to about 8/32 tread when I lose flat protection and give up on them. The only "tougher" tires seem to be short-lasting winter 8 plys like Les Schwab's Maxxis MA SLW in 215/65/16.
Am I on the right track?
AnswerBill,
I am a little confused and a little concerned.
On the one side, you say you wear the 97-98 LI tires down to 8/32nds, then on the other side plan to go with a 97 LI tire that is not only expensive but has long wear properties. Wouldn't it make sense to use a less expensive tire, even if it had poorer wear characteristics?
But I tend to go with load carrying capacity as the most important issue. Tire Rack lists a Dunlop with a 102 LI in the 225/60R16 size.
You mentioned a different tire size and I see that Continental makes a 109/107R in a 215/65R16 - and that seems like a viable option.
