all due respect I have over 1500 rounds of 40 cal in my garage and and know full well that a piece of gravel stuck in the tire would do more to un-balance a tire then a piece of brass or nickel that ways less then 1/4 of an ounce. I mount and balance my own tires to I don't use wheel weights I use plastic beads for airsoft guns 7oz for 33" tires and 1oz to every inch you add to the diameter. I have even ran tires with no weights and the arent effected by anything less then about 3 ounces out of balance. I have had tires (big ones 37") that were 12 ounces out of balance. They ran perfect with 10 ounces of beeds in the tires. even small radials weigh in at 60-70 lbs of rubber/steel or aluminum/ and air. 1/4 ounce won't make a difference and no the tires are not balanced with the valve cap on. Infact in most cases your lucky if you get the same ones back from the tire store since they have thousands laying around on the floor.