Different rubber tyre compounds?

[Matt]

What exactly does R3, M2, M3 etc mean when it comes to tyre compounds? Does anyone have a guide on what's what?

Matt.

[Dan]

i think m3 is the softest compound. r3 is longer lasting but not as soft

[Dan]

i found this on prolines website:

M3 compound specifically designed for more dusty/loamy surfaces.
R3 is designed for blue-groove surfaces