ONE of my front tire went bad,I got me a new one same kind as the the other good one in the car with almost same amount of thread left.
Should I balance just the new tire or both.

 

yeah balance the tire, the other one should already be balanced if you haven't changed anything. Now are you wondering should you get an alignment of the fron t end is different. most problems are tire, but if your hitting lots of curbs or pot holes you might get an alignment

 

If I take one from the rear and put it up front instead ,same things apply right.

 

yeah the tires are balanced when there mounted to the tire. They should still be balanced where ever you rotate them to. A normal price for a mount and balance is about $20.00 per tire.

 

If you feel any steering wheel vibration at any speed you should get the tires balanced. I get mine balanced almost every 5 to 7k. Some tires simply do not wear perfectly, especially if you have a damaged wheel.

I have a lifetime balance contract with Wal-Mart. They rotate & balance my tires every 5k. It cost something like $7 per tire.