Adjusting road bike front derailleur?

The other answer is right. If you bought your bike in a shop and it doesn't shift properly you should return an ask them to correct the problem. If you break something you could void your warranty. You may not have adjusted the high limit screw correctly which would prevent the chain shifting to the big sprocket no matter how tight the cable is. If it is as tight as you say it is, you could break your shifter, the cable, or the derailleur. Now id=s the time to go back to the shop where you bought your bike