So it's time to buy some new wheels. What hardness should you get? What do the durometer numbers mean? What's a durometer anyway? Don't worry, we got you.

Instron Corp. is marketing its new Shore S1 Durometer, which features a modular cartridge system. The system allows operators to test in any of the standard Shore scales-A, B, D, C, DO, O, OO and M.

To avoid these problems, engineers should use a Shore O durometer when measuring the hardness of foams. Its ball-shaped indentor is better suited for foam. And the foam should be at least 0.25 in ...