It depends on what you mean by "hold air". Because of the physics of the thing the tube can't keep up the pressure and so air somehow 'magically' leaks out over time. I pump my tubes up to about 100 psi and then the next day it will be down in the 80-90 psi range. I have to air them up every time I go ride. Now if you can't hold pressure long enough to ride then you have a leak and need to repair/replace the tube. If the tire pressure gets a little low and the tube is getting squashed--especially if you hit a bump--it can get 'pinched' by the rim and you will have to repair/replace it. There are lots of good videos online that will show you how to go about replacing the tube. Pretty simple and can be done in just a few minutes.