Trading bishop and knight for rook and pawn

I seem to reach this position or variations of it many times during games and I am wondering if it is worth trading the bishop and the knight for a rook and pawn when my opponent has castled. I usually take the trade as white because it exposes my opponents king but as I am not very experienced I figured I would ask others opinions. Thoughts?

This is the most basic situation I can think of where this occurs.

It's too soon in the first diagram - seems to me all it accomplishes is throwing away your only developed pieces and handing black the initiative.  The consolidating move Kg8 still leaves black a tempo up.

I agree, i think it is too early in this situation, later in the game it COULD be a good move, but only in pretty limited circumstances. if you were taking the G7 pawn, my opinion would be much different

B+N is almost always better then a R+P. The only case where it might be the other way around if the rook is behind a passer that is far up the board and the rook has alot of mobility and/or the bishop and/or the knight are bad and imobilized.

+1

People who exchange two pieces for Rook and pawn in the early middlegame are normally doomed to failure. The two pieces gang up and start stealing pawns.

b and kn are playing peices

but pawn and rooks sit around till end game and in that time u lost because of lack of playing peices

I am admittedly not very good at chess, (with a rating just under 1000) but i have read several books about how to improve on your chess game(s). One of those books was Pandolfini's Ultimate Guide to Chess. Sadly, I lost the book about 2 months ago,(still looking for it.....) but i remember a paragraph in his book that refers to this situation. He stated that in a situation like this, in the middlegame a rook and pawn were worth about 6 points (or as he preferred to state it, pawns) but a knight and bishop were worth about 7. When you consider that some books refer to the bishop and knight (or at least the bishop) is worth 3.5 pawns instead of 3, this is understandable. In the endgame however, its another story...

The trade IS ALMOST ALWAYS BAD BECAUSE:

1) The enemy King is completly safe. Forget any thoughts such as "with this trade i expose the king"...because you dont.

2) Rooks are fairly weak in the first stages in the early stages of the game (e.g first 20 moves) thus, by trading for a rook+pawn your are handicapping yourself (at least for a while) 

3) Even in the endgame, I think a Knight+Bishop is generally better than Rook+ pawn. So, its not even clear that your middlegame "handicap" is even tempoary

In the book "Basic chess endings", here is what Reuben Fine says:

"Rook plus one pawn vs two pieces is usually a draw,although either side may have winning chances ...When there is nothing else on the board, R+P offers no winning chances at all, since the opponent can if he wishes give up one of the pieces for the pawn."

In sum there is no general rule, but the positions tend to be drawish. But if you are saddled with a deficiency such as a bad Bishop, the Rook has a better chance expecially if he can get behind a passed pawn or get attacking chances such as having control of an open file. OTOH in the early game before the rooks get into play, one is unlikely to get a mating attack when a bishop and a knight have been exchanged away.

Finally, there are a LOT of more important considerations in a chess game that one should concentrate on, such as outpost knights, bad bishops, control of open lines, isolated pawns, and so on.

Note alsothat if you are trading two pieces for a rook in the early game, you are exchanging two pieces that have moved against one, which means that it is likely that you have handed some tempi and therefore the initiative to the opponent. For example suppose that the opponent has castled (one move) and that you have moved your knight and bishop and a pawn to exchange for that rook in a combination. It will have taken at least 3  knight moves and 2 bishop moves to get there, which means that you could be up to 4 tempi down after the exchange! Against a strong player being 3 or 4 tempi down usually means that he has a winning position, so think twice about doing it...

The case where it is usually worth it to exchange the two pieces away is when it is necessary to break up an enemy combination, but one should always look at the resulting position first - of course if you are going to be mated, there is no  hesitation.

As for the position you show, DON\T DO IT!  Stockfish shows this position after the exchange as won for Black!

For example
rnbq4/pppp1kpp/5n2/2b1p3/4P3/8/PPPP1PPP/RNBQK2R w KQ - 0 1

Analysis by Stockfish 1.7.1 JA:

1. -+  (-1.57): 3.d3 d5 4.exd5 Qxd5 5.0-0 Bg4 6.Qe1 Nc6 7.Nc3 Qd7 8.Bg5 Kg8 9.Qd2 Rf8 10.Rae1 Be7 11.a3 Be6 12.Kh1 h6 13.Bh4 Bd6 14.Bxf6 Rxf6 15.Ne4 Rf8 16.f3
2. -+  (-1.61): 3.Nc3 d6 4.h3 Nc6 5.d3 Kg8 6.Be3 Bb6 7.0-0 Be6 8.Bxb6 axb6 9.f4 Nd4 10.fxe5 dxe5 11.Rf2 Qe8 12.Qd2 Qg6 13.Qe3 Bd7 14.Raf1 c5
3. -+  (-1.97): 3.c3 Nc6 4.d3 d5 5.Nd2 Bb6 6.0-0 Kg8 7.Nf3 Bg4 8.Re1 Qd6 9.Be3 Rd8 10.Bxb6 axb6 11.h3 Bxf3 12.Qxf3 dxe4 13.dxe4 Qe6 14.Red1 Rxd1+ 15.Rxd1 Qxa2 16.Qe2
4. -+  (-2.14): 3.0-0 Nc6 4.d3 d5 5.exd5 Bg4 6.Qd2 Nxd5 7.Nc3 Kg8 8.Ne4 Be7 9.c3 Nf4 10.f3 Be6 11.d4 Bc4 12.dxe5 Ne2+ 13.Kh1 Nxc1 14.Rfxc1 Nxe5

Let it ride

In open games with few pieces left the Rook is better imo.

However at the start of the game I agree on the "dynamic pieces" advice.. keep the bishop+knight

how about if you exchange the knight and bishop for a rook and 2 pawns? Just found my self in a situation and i did change, at the moment i am in +1 conserning material.

Actually, turning on the evaluation bar and stockfish says the knight and bishop are still slightly better. It has to do with the max amount of controlled squares.

I think it has to do with this being am early middlegame. In the endgame, pawns and rooks go up in value.

This position is better for white.