On Rubber
Murat: I would be very surprised if there is any difference in the performance of a trigger mechanism's release cycle as a result of new rubbers. These are usually quite robust, and the differential in the force applied to the trigger mechanism as a result of rubber changes would be relatively small.
I have been a lurking member of this forum for some time now, and often see divers saying one rubber is more "powerful" than another, and they only use this rubber or that rubber. And this one is more powerful because its red, and that one more powerful because its green, black … insert a colour.
In terms of comparing the power of one set of rubbers to another it is not technically possible to do this without ensuring that the rubbers are the identical length and are being stressed under identical conditions. Only then, and under quite precise circumstances, will it be scentifically verifiable that one rubber is more "powerful" than another.
Rubber is measured by the pulling power, usually measured in pounds, that it can exert at a specific length, usually measured in inches. So it is very possible to have 12 inch 20mm rubber bands elongated to 60 inches provide less "power" in a given setup, than an 8 inch 16mm rubber bands elongated to those same 60 inches. The reason for this is that the 16mm rubber has been elongated further as a percentage or its resting length. So power per se, is all a question of unique circumstance, and in truth, my experience and its all up to individual preference in the end, is that providing you are using rubber from a reasonably credible supplier the differences in performance are really quite negligable.
A good place to checkout a design for setting up an environment for testing rubber can be seen here:
http://rocknfish.com/Rubber_Test.html
You can see how he has the scale there to provide the poundage readings, and has marked off the various lengths for measurement. In the past we have used a fence strainer (available in most hardware stores I would imagine) to provide the pull. The scales on the other hand are expensive and quite hard to come buy.
You can read more about rubber here:
http://www.sumora.com/selectingrubber.php
But the real rubber guru, or so I am told, is a chap called Moari (Sp??), somewhere on his site is a substantial chart of all sorts of rubbers that he has tested, and their various readings and power ratings. Its quite impressive. I don’t have the url to hand, but I am sure it is out there, and another member of this community knows how to locate it.