Depending upon how much extra length your existing chain has, it may very well be too short for a 4 teeth-larger big chainring. The Biopace ring further confuses the matter. Probably the best is to replace your chain with one which is correctly-sized for your new crankset. If there is much wear on your cassette the new chain may skip, requiring it to be replaced also. You will also probably need to move your front derailleur higher to accommodate your new crankset.