I have signed up to do the London to Brighton Cycle ride in June. As my training milages are getting longer I decided it would be good to have an extra drinks bottle on my hybrid.The main problem being that the existing water bottle position on the down tube and the frame being quite compact, wouldnt allow for an extra one on the seat tube. I took the existing one off and zip tied another to the seat tube in the position I thought it should be. Then by offering up the existing one found that it had to go up the down tube by about an inch.
I was lucky to find a piece of 13mm x 5mm stock aluminium in my offcut box. I marked this 10mm up from the bottom and a centreline up the middle of the 13mm. From this point i marked at 25mm. Also from that first point I marked 64mm (the pitch of the bolt holes on a bottle cage) and then another 25mm from that one. These were then drilled with a 3mm drill bit. The first hole and its coresponding one 64mm away were then opened up to 5.5mm then counterbored for the screw head. The remaining two holes were opened up to 4.2mm and then tapped with an m5 tap. The rest of the bar was cut of with a hacksaw another 10mm from the last hole then rounded off with a file. This was now screwed to the holes in my frame and the cage screwed to the m5 holes, moving it 25mm up the frame.
Now I turned my attention to the second cage. I measured from the top hole in the cage to the underside of the top tube then cut the zip ties. That measurement was then marked on the frame with a scribe and a second one 64mm below. The centre of the tube was then scribe at these points "by eye" but I could have been more scientific if I hadnt just got carried away! I then centre punched these using an automatic center punch which didnt need a hammer swinging around inside the frame.
Now the scary bit. I have a cheap angle drill head which goes in your normal drill chuck. I started with a 3mm bit and carefuly drilled a hole through each centre dots. This I then opened up to 7mm which is the correct size for the rivnuts I was using. The rivnut was then screwed onto the tool and pushed into the 7mm hole and the tool sqeezed by hand inturn squashing the rivnut into place. After the tool was unwound this was repeated on the bottom hole leaving me with two profesional looking m5 bosses in my frame. Quickly I screwed the second cage into position then the first back on too.
If your bottom bracket isnt a sealed one like mine you now need to remove the swarf that would have gone down the seat tube when drilling the holes by removing the bottom bracket, cleaning then replacing (alternatively take it out before you start). I cleaned the bike with bike cleaner then a wash down to get any swarf of the frame and away from the chain and chainwheels. Cant wait to try it out when the rain stops!!! AHHH!!! the sun is shinning over Kent Tonight and the bottle cages have just had a ten mile test run with nothing to report.
After my training rides then the 54 miles from Clapham Common, London to Madera Drive, Brighton I have had no issues with the rivnuts, I had read negative reports on different sites but now laid my mind to rest. I have even done this to my old steel mountain bike with similar results.