On 01/24/2011 09:50 PM, Mark Stonich wrote:
> At 9:04 PM -0500 1/24/11, Marcus Coles wrote:
>> It wasn't just a Trek thing, I have a couple of Jim Miele "Bianchi"
>> bikes from around the same time frame with one piece head tubes with
>> false lugs.
>> I believe these bikes were sourced in Japan.
>
> I first saw these on small Sekai road bikes in about '76.
>
> The problem was that in order to take that much forming they had to be
> made from relatively soft metal. And the headset bearings on a small
> frame are close together so there was a lot of leverage on them. Small
> road frames were usually ridden by small people. So while there were a
> few failures they could generally get away with it. But then Trek and
> (and I suppose others) used them on MTB frames. Larger riders for a
> given frame size, shallower head angles and more abuse led to lots of
> bellmouthed "head tubes".
One-piece "bulge-formed" head tubes were used by Trek and many other companies, but in the mid-80s Trek started using an investment cast one-piece head tube. This was much stronger than the bulge-formed head tube, but much heavier as well. The investment cast head tube can be identified by the "TREK" name cast into the pseudo-lug:
http://pbl.gatech.edu/
--
-John Thompson (john@os2.dhs.org)
Appleton WI USA