TXWY EXCURSION DURING LNDG PROC ROLLOUT.

Narrative

FO MADE A NORMAL LNDG ON RWY 26 AT IAH. I TOOK CTL OF THE ACFT AT APPROX 80 KTS DURING THE LNDG ROLL. I MADE THE DECISION TO ROLL TO THE END OF THE RWY DUE TO THE ACFT SPD AND RELATIVE POS TO THE LAST HIGH SPD EXIT. APCHING THE HIGH SPD EXIT; TWR TOLD US TO MAKE THE HIGH SPD EXIT. I INCREASED THE BRAKING AND TURNED TOWARD THE EXIT. DUE TO THE SPD I HAD TO MAKE A WIDE TURN TO MAKE THE EXIT. OUR R WHEELS CAME CLOSE TO THE EDGE OF THE TXWY; BUT I COULD NOT DETERMINE IF THEY HAD GONE OVER THE EDGE. AFTER INSPECTING THE WHEELS ON THE GND I STILL COULD NOT DETERMINE THIS. 2 DAYS LATER I FOUND OUT THAT A PAX HAD RPTED SEEING MUD FLY UP UNDER THE R WING AS WE TURNED OFF THE RWY. HE CALLED IAH TWR. THEY CONTACTED OUR POI; WHO CONTACTED OUR CHIEF PLT'S OFFICE. IN A LATER MEETING WITH THE CHIEF PLT'S OFFICE IT WAS DETERMINED THAT MY CREW AND I WOULD GET A LINE CHK ON MY NEXT SCHEDULED FLT. SUPPLEMENTAL INFO FROM ACN 261521: AT THE TIME WE WERE NOT SURE WE RAN OFF THE EDGE. WHEN WE BLOCKED IN AT THE GATE; THE CAPT AND I WALKED DOWN TO THE GEAR. I SAW A SMALL AMOUNT OF MUD STAIN ON 2 TIRES. I ASKED THE CAPT IF WE NEEDED TO DO ANYTHING AS FAR AS PAPER WORK OR ANYTHING. HE SAID 'NO; GO ON HOME; EVERYTHING IS OK'.