For the purpose of carrying water, gas, or whatever.
What bike has the most volume in the hollow chambers of the bicycle frame?
1920's De Dion Bouton Propeller Bicycle https://www.carandclassic.co.uk/car/C1077449
For the purpose of carrying water, gas, or whatever.
What bike has the most volume in the hollow chambers of the bicycle frame?
1920's De Dion Bouton Propeller Bicycle https://www.carandclassic.co.uk/car/C1077449
If I was a (stupid) drug dealer and I had the (stupid) idea of asking Stack Exchange the best way to smuggle drugs in the frame of a bicycle, I’d use a time trial bike.
However, I’d be quickly caught because customs xrays can easily penetrate bike frames and detect organic materials; or I’d go out of the drug business because carbon fiber time trial bike frames are quite expensive and i might find that I’d make more money selling the frames than the drugs (jk).
Thinking of standard bikes there are some ways you can maximise the volume. While they may not get you the absolute biggest they'll get close enough that you won't notice the difference. First you want a big frame. The largest size that fits you in something with a long wheelbase - perhaps a trekking style hybrid. Then you need fat tubes. Some bikes - particularly cheap ones these days - make a feature of "oversize tubes"; in general aluminium tubes come up larger than steel or carbon fibre. But not too heavy as some of the extra weight will come from increased wall thickness. This probably means something that tells you what grade of aluminium it is.
At this point though, your problems are only just beginning: you would have to get the liquid in, and keep it in until you want to get it out. The various tubes should be regarded as separate volumes anyway, so you'd be trying to turn the bigger ones (toptube and downtube) into tanks. The downtube would nearly always let liquid out at the bottom bracket and in other places; sealing them all up would take some effort and involve stripping the bike down a long way. The toptube would be easier but even a generous estimate gives you a max of under a litre and a touring bike with big bottles in 3 standard cages could already carry 3 litres. Any liquid you put in the frame would be likely to get contaminated anyway, at least as regards drinking (any many fuels could damage paintwork getting them in/out, or strip grease from necessary places. If you want ballast there are better ways too.
You got to use a custom body one that has larger tube diameter and totally sealed on joints. It would possible for some local machinist, but it would be definitely one weird bike.