A C414 FLT CREW EXITS THE TXWY WHEN LOSING BRAKING TO THE R GEAR AT INT; NC.

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OUR COMPANY OPERATES A RAM CONVERSION; LIQUID COOLED C414 AS A 2 PLT AIRPLANE -- ALTHOUGH LEGALLY IT IS SINGLE PLT. I WAS THE PNF; BUT RETAIN PIC RESPONSIBILITY. WE WERE TAXIING ON THE PARALLEL TXWY FOR RWY 33 AT INT AND NEARING THE HOLD SHORT THRESHOLD LINE. AS THE PF ATTEMPTED TO STOP; HE HAD NO R BRAKE ACTUATION OR 'LIVE PEDAL.' AS THIS IS A CASTERING NOSEWHEEL; THE ACFT IMMEDIATELY TURNED L. I (PNF) IMMEDIATELY APPLIED FULL R BRAKE/PEDAL WITH NO ACTUATION. WE STOPPED JUST OFF OF THE TXWY AND NOW HAD FULL BRAKE AUTH ON BOTH L AND R AND BOTH PF AND PNF POS. WE REQUESTED PERMISSION TO TAXI BACK TO AN APRON AREA TO INSPECT THE ACFT. AFTER INSPECTING AND TAXI TESTING THE ACFT; WE COULD NOT REPRODUCE THE MALFUNCTION. WE CONTINUED TO ROC WITH NO FURTHER INDICATIONS. AS A PRECAUTION; WE HAD THE BRAKE SYS FLUSHED. IT IS THE CREW'S BELIEF THAT THE COMBINATION OF A LONG DOWNHILL TAXI AND A COLD SOAKED ACFT MAY HAVE BEEN CAUSAL (ICE AT MASTER CYLINDER). STOPPING; EVEN THOUGH IT MEANT LEAVING THE TXWY; WAS THE ONLY COURSE OF ACTION; AS THE ACFT COULD NOT BE ALLOWED TO CONTINUE STRAIGHT AHEAD. THERE WAS NO DAMAGE TO THE ACFT; ARPT LIGHTING; AND NO COMPLAINTS FROM THE TWR. I DON'T KNOW IF THERE WAS A 'FOUL;' BUT WE THOUGHT THAT YOU SHOULD KNOW.