Is there a certain size tube for my tyres? When it comes to fixing bikes, i'm not to crash-hot. I can clean grime, oil the chain and put it back on if it falls off. However, when it comes to the inner tubes I usually rely on someone else to get me another tube and put it on for me (I can put them on, but in that sense I'm too lazy). So, today, when I went to pump up the tyres I found they had a puncture and I would prefer to change them as I haven't ridden this bike in a LONG time, only I'm not sure if there has to be a certain size tube. Help? Please? :)
Each tube reference size fits a certain number of tire sizes.
For example, I ride 700x23c tires and my tubes are 700-18-23c.

So just find out the size of your tire (should be written on the sidewall) and go out for a tube that will hav this tire size in its fitting range.

Be careful about the valve specification too. get a tube with the same valve type as your previous tube/as your wheel supports : http://sheldonbrown.com/gloss_u-v.html#valve