What is the difference between dual ply and single ply tires?

Why, one ply, of course!

Think of one ply as one thickness and dual ply as double thickness. Basically, two layers of rubber rather than one.

thanks

Bascially, the more plys, the better. You make very thin plys and lay them in different directions, making the product stronger.

I believe the ply refers to the layer of fabric cast into the rubber. This is what gives a tire its strength. In a car tire you have radial plies that run straight from bead to bead and bias plies that run at an angle from bead to bead. Bike tires are bias ply.

Normally the more plies you have the more load the tire can carry safely, but you can also make the ride harsher with more plies depending on the type of fabric used in making the plies. On car & truck tires for example the load range letter corresponds to the number of plies used, for example a load range letter D is a 8 ply rating while a F range is 12 ply and the more plies the more load it can carry.

Most bicycle tires today have at least 2 plies, some use Kevlar as the first ply and either cotton or silk (these two are rare today), polyamide, polyester or nylon (more common today) for the second. Most tires I believe now use 3 to 4 plies such as Michelin Axial Carbon, while the Conti Grand Prix 4 Seasons uses 5 plies. But there is more here than just the number of plies, there is also something called TPI (treads per square inch) the more the better, some have only 33 and some have 430. The more expensive tires have a higher TPI count.

Then the best tires must be my 4 ply intense. Try putting 2 - 4 pound tires on your xc bike

You dont know nothing about tires

Well, you "don't know nothing" about the English language, you flaming hoodlum.

Why not share your expertise with the rest of us ignorant people here?