I get it and understand that a wheel becomes out of balance when one section of the tire or rim is heavier than the others and needs weights added to make it even. So how does one section become heavier? Are not rims and tires manufactured evenly through out? Or is it mostly when tires wear out? If that’s the case, then why do brand new tires and rims need balancing?

 

They are not.



They do.



Because they are not made perfectly.

 

Rims can be slightly bent too. I have one that requires weights on both sides of the rim to balance right.

 

tires are not perfectly round. The belts/fibers are not perfectly distributed. tires are not perfectly weighted in every direction

Wheels are not perfectly round. Wheels are not perfectly cast (forged wheels are usually better) so that they are equally weighted in every direction

Now add in tire pressure monitor sensors that put weight in a small area, plus valve stems.