I emailed lots of people, and talked to the experts but no-one seems to know what is causing this. If you mess up the offset they should clatter all the time according to Brian Nutter at Wiseco. I think there is something in the design or the recomended clearance is too high when they coat them and the pistons don't expand enough. From my survay, about half of the people who responded have had problems with light load mid rpm clatter, WHICH statistically is not good :(... But I'm already in too late in the game so I'll go with them. My suggestion is for Arias and make sure to go LOW on the piston to wall crearance. I think that is how most tunning shops do it. They just bore tighter since they know the customer is hardly going to push the engine 10/10ths for extended periods of time. Wiseco's design pistons for racing and those guys don't care about clatter and such, that and their clearace is made with the highest expansion factor in mind :)
