is it normal? to be going 20mph uphill in a 1989 325ix(all-wheel drive) and not be able to slam on the brakes and stop in time for a squirrel to cross?(R.I.P) my car has a recently bleed system and renewed brake fluid, also brand new from brake pads the rears are about 50% worn. could it be the brake booster or should i rebuild the master cylinder or what?