may have said:
Werehatrack said:
The string test for rear dropout centering is a good ballpark test,
but bear in mind that many older aluminum frames were found to be
misaligned when new due to the warpage induced in heat-treating the
frame. Thus, you could have an uncrashed aluminum-frame bike
(perhaps
Quoted message said:even with a major name brand involved) that has never been straight
since day one. Sometimes, the bike will ride just fine, and
sometimes
Quoted message said:it will ride just well enough to outlive the interest of its first
owner.
I'd be interested in some evidence of this "never straight since day
one." How often is a new Cannondale out of alignment? How do you know
this?
Early on, it was reportedly common enough with that make that they had
numerous returns, based on the statements of a couple of CDale
dealers, at least one of them here in this newsgroup. I ran across a
CDale that was likely an undetected example of such not too long ago;
an acquaintance dropped by with a an older near-mint unit with an
aluminum frame that he'd just picked up for very little, and when I
looked at it, something seemed odd; one piece of string later, it
became obvious that the seat tube was about 6mm off the centerline of
the frame. There wasn't a scratch or dent anywhere on the bike, and
it rode well, so he decided to ignore it. The owner of a local store
that specializes in used bikes had also advised caution in evaluating
used aluminum-frame bikes for purchase when I was shopping for a
mountain bike a couple of years ago; he openly warned that there were
some which were warped to begin with, and the misalignment wasn't
always caught by the assemblers. That said, he also noted that it
wasn't common...but it shouldn't be ignored as a possible issue,
either.
Quoted message said:I ask because, according to what I've heard, Cannondale has always used
alignment fixtures to re-align the important points on the frame after
heat treating, those points being the dropouts, bottom bracket, head
tube, seat tube, brake attachement points, etc. (At least when I
bought mine, they did not bother to perfectly straighten the tubes
between those points.)
More likely, they *couldn't* perfectly straighten them after the
heat-treat process.
Quoted message said:They were able to do this realignment because after the quenching stage
in the "precipitation hardening" heat treat, the aluminum is dead soft
and easy to realign. It gains its hardness and strength only after the
"aging" part of that heat treatment.
Yeah, aluminum is a whole different thing from steel when it comes to
hardening.
Quoted message said:I haven't heard of any problems with their scheme, assuming one can
accept a seat stay that's not cosmetically straight. If you have heard
of problems, I'd be interested.
The measures that you describe were evidently adopted after they
discovered that they'd already shipped a bunch of frames that had
problems. Yes, later units have been (from what I've heard) very good
in those areas, but they definitely made some that had all sorts of
alignment issues that weren't fixed before the frames got out the
door. Even after they got the alignment of the critical points nailed
down, as you noted, they still were producing frames which had visible
snakiness in tubes which varied from one frame to another. ISTR one
comment from a CDale dealer that they would point out the variations
as being a feature; each frame was really unique. It must have made
for some interesting conversations.
I've never seen a CDale with a non-straight seat tube or top tube that
wasn't due to a collision, though. I've noticed seat stays and chain
stays with "artistic features" a number of times, but only the one
personal instance of a frame with something out of whack where it
could have mattered, and even then, the buyer didn't seem to find the
result objectionable. Still, if I were looking at a used bike to buy,
I'd check it anyway, just in case. If it's something that's going to
make a difference, it doesn't matter whether a fault was present for a
day, a week, or a decade; it's still better to find it before laying
the money down. (In the case of that off-center CDale, though, the
guy would have had a decent deal even if the frame was junk; he paid
all of $60 for it, and the wheels had no wear on the brake surfaces.)
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