TKOF ABORTED WHEN ACFT PERFORMANCE NOT AS EXPECTED ON INITIAL TKOF PROC.

Narrative

OUR FLT ABORTED TKOF AT 70 KTS WHILE DEPARTING RWY 4 IN KLEX. WHEN WE WERE CLRED TO TKOF; WE TAXIED INTO POS ON RWY 4 AND HELD THE BRAKES WHILE ADVANCING THE PWR TO 1.4 EPR. THIS WAS ACCOMPLISHED AS BRIEFED. IT WAS DONE TO ENSURE A GOOD PWR CHK AND MAXIMIZE TKOF PERFORMANCE GIVEN A FAIRLY HVY DEP ON A RELATIVELY SHORT RWY (RWY LENGTH 7002 FT). ALL INDICATIONS WERE NORMAL. AS THE TKOF ROLL PROGRESSED; A SUBTLE 'SPONGY' FEELING WAS DETECTED. ALL ENG INDICATIONS WERE ABSOLUTELY NORMAL. IT WAS THE FO'S LEG; BUT MY HAND WAS ON THE THROTTLES. DUE TO THIS 'SPONGY' FEELING; I SUSPECTED SOME TYPE OF TIRE FAILURE AND ELECTED TO ABORT THE TKOF. IT WAS A LOW SPD ABORT AND DECELERATION WAS VERY COMFORTABLE. WE ADVISED ATC THAT WE HAD ABORTED THE TKOF. WE TAXIED DOWN TO A5; CLRED RWY 4 AND THEN WERE CLRED TO THE RAMP BY ATC. WE COMMUNICATED TO ATC WE SUSPECTED SOME TYPE OF TIRE FAILURE AND WOULD BE RETURNING TO THE GATE. WE THEN MADE A PA TO THE PAX STATING SAME. WE CONTACTED THE RAMP AND DESCRIBED WHAT TRANSPIRED. WE HELD SHORT OF THE GATE AREA WHILE A GND CREW INSPECTED THE TIRES. AFTER THIS INSPECTION; WE PROCEEDED TO THE GATE FOR A MORE COMPREHENSIVE INSPECTION; I.E.; TIRE PRESSURES; FOD DAMAGE; ETC. A LOGBOOK ENTRY WAS MADE AND CONTRACT MAINT WAS CALLED TO INSPECT TIRE PRESSURES. I PROCEEDED OUT OF THE ACFT TO INSPECT THE ENGS AFTER I WAS INFORMED A LARGE PIECE OF TAR; APPROX 12 INCHES IN LENGTH; 4 INCHES WIDE; AND 1/2 INCH THICK WAS LODGED IN THE INBOARD TREAD OF #3 MAIN TIRE. FROM THE GND I WAS FAIRLY CERTAIN SOME FOD HAD OCCURRED. MYSELF; ALONG WITH THE STATION MGR; WALKED UP A BAGGAGE CONVEYOR POSITIONED UNDER THE R ENG FOR A CLOSER LOOK. A TAR BALL WAS LODGED IN THE INLET GUIDE VANE AT ABOUT THE 10 O'CLOCK POS. ADDITIONALLY; SOME FAN BLADES WERE CHIPPED AND BENT FORWARD. I INFORMED THE STATION MGR THAT THE ENG WOULD REQUIRE SOME TYPE OF ENG INSPECTION. I PROCEEDED BACK TO THE ACFT AND INFORMED THE CREW OF THE PROB. I THEN INFORMED THE PAX THAT; DUE TO A MECHANICAL; THE ACFT WOULD NOT BE ABLE TO PROCEED TO ATL AND THAT THEY SHOULD PROCEED TO THE MAIN TICKET COUNTER FOR FURTHER INFO.