HS125 LANDS SHORT OF RWY WHEN PIC; PF; HAD SUSPICIONS ABOUT HIS BRAKING CAPABILITIES AFTER HAVING HAD A HYD OVERHEAT WARNING LIGHT ON DURING DSCNT.

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I WAS FO (NON FLYING) ENRTE FROM PSP TO SJC; WITH NO PAX. DURING THE FLT; THE 'HOT HYD FLUID' LIGHT ILLUMINATED; AND UPON CHKING 'EMER CHKLIST;' THE COURSE OF ACTION WAS TO CONTINUE FLT AND FIX BEFORE NEXT FLT. THE CAPT AND I CONCLUDED WE SHOULD LOWER GEAR AND FLAPS EARLY TO MAKE SURE NO PROBS WITH THE HYD SYS; AND USE THE LONG RWY. AFTER A WHILE (15 MINS BEFORE LNDG); THE 'HOT HYD LIGHT' WENT OUT. THE CAPT ELECTED TO LAND ON THE SHORT RWY (5000 FT); BUT WOULD LAND ON THE NUMBERS TO ALLOW FOR ANY PROBS WE MIGHT INCUR. FROM 1000 FT TO LNDG; AFTER MY 1000 FT CHKS WERE DONE; I WAS HEAD DOWN INSIDE THE COCKPIT CALLING OUT AIRSPD AND VERT DSCNT RATE. WE HIT FAIRLY HARD AND ACFT STARTED SHAKING. I ASKED WHAT HAPPENED? RESPONSE WAS 'MUST HAVE BLOWN A TIRE.' THE SHAKING WAS VERY SEVERE AND STOPPED WHEN HE LET UP ON BRAKES. THE TWR ASKED IF WE WERE OK AND DID WE NEED ASSISTANCE. THEY OBVIOUSLY SAW THE ACFT SHAKING. THEY ALSO REMARKED THAT WE LOOKED LIKE WE HIT THE END OF THE RWY. AT THIS POINT; I DID NOT KNOW WHAT HAD HAPPENED; BUT SOUNDED LOGICAL SINCE WE HAD NOT BLOWN ANY TIRES. WE CONTINUED OUR TAXI AND THE ONLY SHAKING WAS UPON BRAKING. AFTER STOPPING AND EXITING THE ACFT; THE ONLY DAMAGE VISIBLE WAS BROKEN SCISSORS AND BALD TIRES. CONCLUSION: WE MUST HAVE LANDED SHORT. SHOULD HAVE LANDED ON LONG RWY. SUPPLEMENTAL INFO FROM ACN 620067: RWY 30L WAS CLOSED AT SJC. CHOICES: RWY 29 OR RWY 30R. WHEN LIGHT WENT OUT; I VERIFIED THAT WE WERE LIGHT ENOUGH TO USE RWY 29. I INTENDED TO TOUCH DOWN ON OR CLOSE TO THE RWY NUMBERS. UPON TOUCHDOWN (RATE OF DSCNT WAS NOT HIGH); THERE WAS A JOLT AND 3-5 SECONDS OF INTENSE VIBRATION. THE VIBRATION WENT AWAY FOR A FEW SECONDS; THEN RETURNED. DIRECTIONAL CTL WAS MAINTAINED. WE USED THE BRAKES AS LITTLE AS POSSIBLE DUE TO THE FACT THAT THEY SEEMED TO AGGRAVATE THE VIBRATION. THE TWR SAID THAT WE MAY HAVE TOUCHED DOWN JUST SHORT OF THE RWY. THERE WERE NO SIGNS OF IMPACT DAMAGE. IT DID NOT; THEREFORE; SEEM THAT WE HAD TOUCHED DOWN SHORT OF THE RWY. OUR DIRECTOR OF MAINT; THE NEXT DAY; LOOKED AT THE ACFT. HIS INITIAL THOUGHT WAS THAT THE L SCISSORS RETAINING NUT BACKED OFF. THE REMNANTS OF THE COTTER PIN; HOWEVER; WERE PRESENT IN THE RETAINING BOLT. ONLY AFTER 3 DAYS DID I FIND OUT THAT TIRE MARKS MATCHING OUR ACFT WERE FOUND SHORT OF RWY 29. THE CAUSE OF THE HYD HIGH TEMP LIGHT IS NOT YET KNOWN. THE FLUID LEVEL; CHKED BY OUR DIRECTOR OF MAINT; WAS RPTED TO BE OK. OPINION AS TO CAUSE: TRIED TO LAND TOO CLOSE TO THE NUMBERS. 200-500 FT WOULD HAVE WORKED FINE. I CUT IT TOO CLOSE! A FRACTION OF A SECOND SHOULD NOT MAKE THE DIFFERENCE BTWN A NICE LNDG AND DAMAGE. A LONGER RWY WAS AVAILABLE BUT NOT USED BECAUSE I DID NOT WANT TO TIE UP THE ONLY RWY THE ACR'S COULD USE.