Drillium.

Most vintage bike enthusiasts know about cutouts in frame bottom brackets, but some, especially newbies don’t know the reason. Someone recently asked me why I didn’t put drain holes in my bottom brackets? I was baffled and asked, “Who does that?” He listed frames that had “Drain holes,” and I realized he was talking about bottom bracket cutouts.

It was a fashion gimmick of its time, that’s all. There was no logical reason. Think about it, it is a poor drainage system. The bottom bracket is in direct line of fire from water spraying up from the front wheel. These large holes let in more water than they let out again.

For those who don’t know, here is a history lesson. In the 1970s a craze started amongst cyclists all over Europe, later referred to as “Drillium.” (Picture left.)

Drilling holes in component parts to reduce weight. The fad was huge in the UK, especially amongst time-trialists, who were forever looking for ways to save weight. And of course removing metal reduces weight.

The amount of weight saved by drilling holes in aluminum components was miniscule, but it didn’t matter.

It was a way to customize a bike and a few more holes than your competitor was a psychological boost if nothing else.

If your bike had so many holes, it had no shadow, you were a winner, in style anyway.

Component manufactures were quick to follow this trend, and for example, a seat post that was previously round and smooth, now had flutes machined in them. Frame builders too got on the band wagon. A large hole cut out of a bottom bracket shell, was a considerable chunk of steel that was no longer there.

Of course all these holes and flutes created more aerodynamic drag, but no one thought of that at the time. Aero bikes would be a future craze.

Frame builders used a special die and a press to stamp out these cutouts in seconds. Holes were similarly stamped in lugs before the frame was assembled. It also gave framebuilders an opportunity to individualize frames with cutouts in the form of their logo. It was done for brand recognition.

My newbie inquisitor was still not satisfied. “If these are not drain holes in the BB, then why weren’t they engraved?” I’ll tell you why. Holes can be stamped out in seconds, but engraving takes time, and is super expensive. Especially engraving on a curved surface.

I know this because I had my name engraved in the top of the BB shell.

It had to be done with a special fixture that rotated the shell as the engraving progressed, so the router bit that does the cutting is always at right angles to the curved surface of the BB shell. (Picture right.)

It is a highly skilled operation and is one of the reasons my custom frames cost so much. If you see what appears to be engraving on the bottom bracket of a production bike. Things like lettering, a logo or grooves. It was most likely cast that way. The design was in the mold.

Just as my custom frames had my logo engraved in the crown, whereas my production Fuso frame had the name cast in it. (See above.)  I had to buy 1,000 crowns to get that feature. So why did my Fuso not have a cutout BB? By 1984 when production on the Fuso started, the fashion had run its course.

Some Italian framebuilders continued doing cutouts, but remember they had dies to stamp the holes. I was not about to invest that kind of money for the tooling and a press, for fad that had run its course, and was dying out anyway.