The Teuton's Alexsandr Nevsky fought were famous for their dreaded wedge cavalry formation. I'm relitively certain it was an offensive tactic to.

As for my tests I discovered the wedge formation did a good enough job hitting infantry in standard formation and crushing right on through to the artillery. (Each time I did this I target the artillery behind the soldiers, not the soldiers.) Against the higher level spears. (German Armoured Seargents.) I lost a lot of cavalry on the initial charge but ended up breaking through anyways. However I lost enough cavalry I probably wouldn't do it in campaign game. (might be worth mentioning my cavalry in that test were Milanese Broken Lances and Men at Arms.) Later though with a unit of Qapikula I destroyed the enemy utterly even though he had good spears. So.. I believe it can be assumed that wedge does a good job of breaking through the enemy. I never had a cavalry unit not break through, all of them did do their job although some wern't as successful... Good cavalry will break through any spear unit. However... pikes are nasty...

Lol. I tried to break through some pikes as France. Noble Knights vs. Terico defending a Basiliac. I ordered men in wedge to attack the Basiliac.. the pike men held firm and brought down my French in droves. However.. I pulled the men out the pikes broke formation I killed them all and won the battle anyways. So Wedge is effective against everything but pikes I believe.