Is a bolt bought from a hardware store a suitable replacement for old bolts on a bike (e.g aerobar bolts, seat bolts etc)? In other words, is there anything special about bike bolts?
Yes, bike bolts are made of a specific hardness, or rating. You should not replace bolts unless they are for bikes and you know what you are doing. You shop should ahave a supply. However, if you are replacing bolts because they are rusted I would not replace them with hardware store bolts. Look for stainless bolts first.
If you want to get some chi-chi bolts in Titanium and aluminum you can find them at www.srp-usa.com and www.racebolts.com