now when you put new tires or rims on your car u have to balance the tires right? What about about if i take them off another car and put them on mine? And if i go from 14' to 16' rims what do i have to make sure i do to make sure my speedometer isnt off.

what they do when they balance is put the tire on a machine that simulates 60mph it then finds the flat spots on the wheel, and adjust how much weight(little adhesive weights) needs to be put on the flat spot, i would def get them rebalanced the min you leave the shop after your wheels are balanced every time u hit a rock a bump in the road ect...... the balancing is affected so if they have been on a car for awhile no doubt they need to be done again