:It's true that above 70 tons mechanical reliability decreases rapidly, so the Swedish variant is at the edge. Comparisons to the Königstiger should take into account however that the older German vehicle was grossly underpowered; the Leopard 2 isn't. Also there have been all kinds of technical improvements since 1945 resulting in tanks that are, even at 70 tons, in practice far more reliable than any tank in WWII, whatever its weight. Yes, modern tanks have their weak spots that even a RPG-7 — preferably not with a tandem charge: that's really only useful for defeating ERA — can exploit. Protecting them completely would make them too expensive. Is that a serious liability? The answer depends on what you want to use them for. If you desire to defeat a technologically advanced enemy, heavy tanks are still very useful. Other tanks are then the main opponents. If you expect to wage urban warfare only, tanks should be a great deal lighter. But not so light as a LAV: light armour is much too vulnerable to serious resistance. So the 40 ton class would indeed be best. However both the M1 and the Leopard 2 can easily be turned into 45 ton RPG-proof vehicles by simply replacing the heavy armour modules with a configuration consisting only of two silicon carbide layers or something equivalent. In fact Australia apparently plans to do just that with its M1's. And in case of real war they are just as easily made real tanks again.