"Doc" <
[email protected]> wrote in message news:<3e8f512e$1_1@newsfeed>...
Hitting just a few of the points
> Last year the axle of my BB broke(Shimano BB UN-51) can I attribute this to fabrication vice or to
> metal fatigue?
In years past bottom bracket spindles did break eventually. With modern cartridge bottom brackets
this is rare. Since modern cartridge BBs are cheap and can not be serviced they are discarded long
before there should be any danger of the spindle breaking.
The spindles in the older bottom brackets did usually last many tens of thousands of miles before
failure though.
I'm of the opinion that your bottom bracket was defective.
> Do metal fatigue exist? I have an old cro-mo touring frame with many thousands miles,is this frame
> will break one day by metal fatigue?
Bicycles are built to last many thousands of miles. For the most part when steel frames fail they do
not do so catastrophically; they give some warning and even when they do fail they often do not dump
you to the ground. The steel frame that I broke creeked for months before the seat stay finally
broke. Several riders I know broke their downtube near the bottom bracket because the builder
overheated the tubes. None of these cases resulted in injury to the cyclist. Breaking a BB or pedal
spindle, crank arm, or stem often does produce injury.
If your frame is well built it should last as long as you care to ride it, if it isn't well built it
should still last a long time and isn't likely to maim you when it does fail.
> I saw some alu frames broke,is steel(cro-mo) will do the same with time? In a century,could I ride
> this old friend without risk?
Other posters ansered this.
> Other question:is the metal (frame) becomming more soft with time? Thanks. Doc.
Steel does not change its stiffness over time. It maintains the same stiffness until almost the
point of failure.
best, Bruce
--
Bruce Jackson - Sr. Systems Programmer - DMSP, a M/A/R/C Group company
