Donald Gillies writes:
>>>> The Mavic 517's on my beloved Marin Team Issue
>>>> won't stay true anymore and the LBS says they are
>>>> ready to go.
>> Well that's basically BS unless they showed you cracks or
>> kinks from crashing.
>>> What the heck does he mean "They won't stay true
>>> anymore". I have only had a single pair of rims that
>>> wouldn't stay true, and these were heat-treated rims.
>>> Once they bent, they NEVER got true again, because they
>>> were just too darned stiff.
>> No matter how much you heat treat aluminum or work harden
>> it, it's elasticity does not change. I suspect the
>> wheelbuilder who made the assessment you express had no
>> idea of how to true a wobbly wheel, or for that matter,
>> what to do if a rim gets a non-fatal wow in it. This has
>> nothing to do with heat treatment.
> irrelevant.
> My rims experienced plastic deformation. the yield
> strength can be increased by heat treating. therefore, if
> the rims had not been heat treated, plastic deformation
> might have been less, or alternately, the higher yield
> strength meant that my spokes could no longer pull the rim
> straight by exceeding the now-increased yield-strength,
> now that the rims had been bent.
That's a different story but a higher yield strength still
does not effect truing the wheel. Besides, I am not the
least convinced that these rims have a higher yield strength
than others, having straightened many wheels with rims of
different designs. If the wheel is bent it cannot readily be
plastically deformed back into alignment with spoke
adjustments. That must be done by first carefully bending
the rim manually until the it is near planar before
beginning with spoke adjustments.
Recently at a coastal hangout, the San Gregorio store, where
an assortment of motorcyclists often stop, one of them
knocked down my friends bicycle and roared away, riding over
the rear wheel and leaving it a pretzel. That was a classic
bend and re-bend exercise after which the re-trued wheel has
survived a few hundred miles. Without careful inspection it
does not reveal its trauma.
> check your facts, jobst.
Those are my facts. I think either your wheel was worse off
than described or you need a better wheel builder. In any
case, when I hear that heat treatment is the culprit, I
doubt the assessment.
Jobst Brandt
[email protected]