Hey guys.

If I was to try and drill a couple of holes in the frame of my bike for an extra drink bottle (its pretty old, and only has the proper holes for one at this stage), will that change the overall durability of the frame? I doubt it will, but I am just checking with everyone, as you guys will probably have more of a clue if it is a bad idea. Thanks.

The holes create a stress riser, which ideally you should fix by reinforcing around the edge of the hole.
Screwing straight into a hole in a thin tube wall might not be strong enough to support a 1.5 kg of water bottle bouncing around. Butted steel tubing will be 0.4mm - 0.7mm thick, and aluminium a bit thicker I guess.

For a factory bottle mount a fine tube is inserted through a hole, all the way until it touches the other side of the frame tube. The fine tube is brazed or glued at both ends. A hole is tapped into the fine tube fo take a bolt. You can glue aluminium and carbon frames at home but there is a bit to it - see the article on making your own carbon frame on SheldonBrown.com for some problems and solutions. It would be simpler to use a clamp-on bottle cage. If your bike is a cheapie it will have a good thick wall so may be fine with just drilling and self-tapping screws.

Topeak make a simple bolt /strap on second mount that you can put on your seattube above derailleur band. Easy.

Simonius_Titius wrote:The holes create a stress riser, which ideally you should fix by reinforcing around the edge of the hole.
Screwing straight into a hole in a thin tube wall might not be strong enough to support a 1.5 kg of water bottle bouncing around. Butted steel tubing will be 0.4mm - 0.7mm thick, and aluminium a bit thicker I guess.

For a factory bottle mount a fine tube is inserted through a hole, all the way until it touches the other side of the frame tube. The fine tube is brazed or glued at both ends. A hole is tapped into the fine tube fo take a bolt. You can glue aluminium and carbon frames at home but there is a bit to it - see the article on making your own carbon frame on SheldonBrown.com for some problems and solutions. It would be simpler to use a clamp-on bottle cage. If your bike is a cheapie it will have a good thick wall so may be fine with just drilling and self-tapping screws.

Wot abouts Rivnuts Guv'na

Whats the frame made of?

I wouldnt do it on one of those Bamboo bike frames, thats for sure.

Its a mountain bike thats about ten years old at least. Made of some kind of metal lol.

if the tube is thick enough to think about tapping ( like my comuter bike is) then the hole is not going to make much differance at all, if its not then dont, but why don't you just get a cammel back tm