MD80 CAPTAIN REPORTS BEING CLEARED FOR TKOF AT ORD WITH WINDS EXCEEDING TAIL WIND LIMITS.

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DURING TAXI TO RWY 32L INTXN T10 TKOF; WE WERE ADVISED BY GND AND ATIS THAT WIND WAS APPROX 080 DEGS AT 8 KTS. A SLIGHT TAILWIND; SO WE SET UP FOR MAX PWR TKOF AND CALCULATED WHAT THE FULL 10 KT TAILWIND WT PENALTY WAS; WHICH WE WERE LEGAL FOR; IF NECESSARY. APCHING THE RWY; WE NOTED ANOTHER ACFT PULL OFF RWY 32L AND HEAD TOWARDS RWY 9L. WE WERE NOT ON THE TWR FREQ AT THAT TIME SO WE DIDN'T KNOW WHY. WE WERE CLRED FOR TKOF; AND AS WE TAXIED ONTO THE RWY WERE GIVEN WINDS 120 DEGS AT 13 KTS. I TOLD TWR IT WOULD TAKE ME A MIN TO CALCULATE THE TAILWIND SO THEY TOLD ME TO CLR THE RWY BY XING AND HOLDING IN THE RWY 9R PAD; THEN CALL WHEN READY. AFTER WE PARKED WE WORKED OUT THE WIND TO BE A 160 DEG TAILWIND AND AT 13 KTS THAT EQUATED TO A 12 KT TAILWIND. WHILE WE WERE DOING OUR CALCULATIONS; TWR CLRED AN ACR #1 AND ACR #2 FLT FOR TKOF; SAME WINDS; WHICH THEY BOTH ACCEPTED AND THEY BOTH TOOK OFF. WE TOLD TWR WE WEREN'T LEGAL AND THEY TAXIED US TO RWY 9L; AND I NOTICED SEVERAL OTHER PLANES FOLLOWING US FROM RWY 32L AFTER WE SWITCHED TO GND FREQ. MY CONCERN IS THAT THIS WAS A HUGE GOTCHA WHICH WE AVOIDED. THE WIND GIVEN JUST AT TKOF WAS SIGNIFICANTLY STRONGER AND FROM A MORE TAILWIND POS THAN ANY OTHER INFO UP TO THAT POINT. ANOTHER PLANE BEFORE US APPARENTLY FIGURED THIS OUT AND CHANGED RWYS. TWR DID NOT GET THE HINT. I TOOK TIME TO FIGURE OUT THE ACTUAL TAILWIND; DETERMINED WE WEREN'T LEGAL; AND APPARENTLY TWR WAS CLRING OTHER JETS FOR TKOF WITH AN ILLEGAL TAILWIND. I KNOW OTHER OPERATORS MAY HAVE DIFFERENT LIMITS; BUT I SUSPECT NOT IN THIS CASE. IT IS MUCH EASIER FOR A TWR CTLR TO HAVE SOMEONE FIGURE OUT THE TAILWIND COMPONENT; THAN IT IS FOR AN AIRCREW; LAST SECOND; IN THE COCKPIT JUST PRIOR TO TKOF.