[Lmn55d]

I'll give it a shot. There are a couple factors that determine the effectiveness of a free showdown raise. The most important, IMO, is how often your opponent will fold a better hand. This is what gives the move its power. Here's an example:

You open from the CO with 9Ts and are called by a fairly weak-tight BB. Flop comes QT6 with a flush draw. You bet and are checkraised. You call. Turn is 4. BB leads and you raise, intending to take a free showdown.

Against a player who could fold TJ, TK, AT or a weak queen, this is one hell of a move. Furthermore, you could still have the best hand because he could be on a draw or have a pair of sixes or something.

There are a couple more important factors:

2) how frequently will your opponent 3bet you with a worse hand. There are a lot of aggressive players who love to semibluff or bluff 3bet, or simply 3bet a weaker made hand because they like it. Against these players, the free showdown raise loses a ton of value (also these types of players tend not to fold a better hand than yours, which goes along with #1). When you make a free showdown raise, you are intending to fold to a 3bet usually. Sometimes you are folding a hand that is best or has a lot more outs than you think. If either of these is likely to be the case, the FSR loses a lot of value.

3) How often will your opponent bluff the river with a missed draw or otherwise weak hand. If your opponent will bluff the river 100% of the time, you'd rather him do this with 0% equity than charge him on the turn when he has equity and might 3bet with a worse hand or simply fold to your raise. MarkD and I did some calculations in an older post about the value of folding a 5-6 outer. This is often overrated. THe pot would have to be pretty big to make this have more value than inducing a river bluff from a frequent bluffer. Some guys will be bluffing a hand that is drawing dead or very slim against yours and would fold to a turn raise, but would bluff the river if you just call the turn. In this spot you obviously want to keep your opponent in. Against an opponent who never bluffs and who will often have a draw, the FSR gains a lot of value.

Like I said in another post, the types of player that the FSR is useful against aren't too common at 5/10, 10/20 etc. Semibluff and bluff raises are so common that nobody folds, even solid playing TAGs. There are some players/situations where it is a very powerful move though. Particularly if a player respects your play. Also, if the turn introduces a new draw, you will lose a lot of folding equity because people will put you on a semibluff a lot.