I believe that Reynolds increased the tube thickness midstream in production to take care of customer complaints about 753 tubing collapse...
Regards, Steve Neago
>
> I was a framebuilder for over 20 years; working with your hands all day
> every day keeps 'em pretty strong, but I was never able to permanently
dent
> the thinnest 753 by hand. Even the thinnest Tange Prestige, at 0.3mm
> (0.012") only 3/4 as thick as the thinnest 753, would flex noticeably but
> not permanently dent, hard as I tried. I have to say I think it's a myth
> that anyone ever dented a bike tube with their hands - unless it was
turned
> to lace by rust!
>
> Greg Parker wrote:
>
> > I've also heard a story of a brazed-on shifter and its boss being
> > pulled off of a 753 DT on a Cuevas, leaving a fatigue-type hole!
> > (Too much heat perhaps?)
>
> Cuevas was vocal about his belief that brass brazing was proper for 753.
He
> must have sent Reynolds a silver-brazed sample to get certified, but then
he
> made all his frames (as far as I know) with brass. I have done
instrumented
> crush testing of frames, and I can tell you for sure that
> quenched-and-tempered low-alloy steels like Prestige and 753 can be strong
> enough despite their light weight, if the heat is kept to a minimum. In
> many cases the thinner heat-treated tube (753) was stronger than the
thicker
> normalized tube (531). But brass brazing on the thin unbutted part, like
> the Cuevas shifter boss, is asking for trouble. The initial crack may
well
> have even started during brazing.
>
> Since the middle of the tube where you're sitting usually hasn't been
heated
> much, at most only a tiny cable housing guide that's almost certainly
> silvered on, it's safe to say: Garth, go ahead and sit on your top tube.
> Just don't quote me out of context... ;^)
>
>
> Mark Bulgier
> Seattle, Wa
> USA