Re: Rear Triangle Alignment -- Will 6mm make a difference I can feel?

On Mar 13, 5:49 pm, carlfo...@xxxxxxxxxxx wrote:
On Fri, 13 Mar 2009 11:25:01 -0700 (PDT), Jeff





<the-dha...@xxxxxxxxxxxxx> wrote:
On Mar 13, 10:16 am, carlfo...@xxxxxxxxxxx wrote:
On Fri, 13 Mar 2009 10:10:11 -0700 (PDT), Jeff

<the-dha...@xxxxxxxxxxxxx> wrote:
On Mar 12, 5:46 pm, jim beam <retard-t...@xxxxxxxxxxxxxxx> wrote:
Jeff wrote:
On Mar 12, 2:47 pm, raam...@xxxxxxxxx wrote:
On Mar 12, 5:38 pm, Jeff <the-dha...@xxxxxxxxxxxxx> wrote:

I just bought a new carbon road bike frame, and when I measured the
rear triangle, I found it offset 6mm to the left.
[snip]
the wheel is centered because of spacers on the axle ? how did you
measure to determine the offset ? care to name the manufacturer of the
frame ?

I used the rear wheel from my current road bike.  The rear spacing on
the carbon frame is correct (130mm) so the wheel goes right in and is
centered left/right in the triangle.  Looks to me like the whole rear
tirangle was laid up wrong (jigging error) at the factory...

I measured the offset using a Park frame jig that grabs the frame at
the BB and has an adjustable "slider" arm (similar to the one on the
Park rear derailleur hanger tool) that you can adjust to pick up the
desired part of the frame.  The you reverse the frame (without
changing the slider arm setting) and pick up the same point on the
other side of the frame.  This is a nice heavy-duty stand that makes
coldsetting steel frames as easy as that operation can get.  (I'm not
sure Park makes that stand any longer -- couldn't find it on their
website.)

if it's the tool i think it is, are you measuring to the outside or the
inside of the drops?  if you're measuring to the outside, you can easily
measure a difference, yet the frame is perfectly straight.  different
thickness drops, etc.  what matters is that the two wheels are centered
wrt each other, and that's measured on the *inside* of the drops.

I guess I could take my current steel frame and introduce a similar
6mm misalignment to see if I can feel the offset when I ride it, but I
was hoping that someone would say "Nah, you won't feel it" or "Yeah,
it will be unrideable" to save me the work and mental anguish of
coldsetting an error into a perfectly good frame...

fwiw, i've seen frames with different thickness rear drops set
"centered" for their outside, not their inside, and thus they were
off-center.  apparently it's a simple mistake to make.

and yes, it does make a difference to ride.

Thank you for pointing that out -- I'll measure the dropout thickness
this evening.  The "6mm" figure I stated was an eyeball; last evening
I actually measured the offset and it is 3.7mm.  I still think that is
a lot...

Dear Jeff,

What's the alignment on your current bike on the same Park jig?

Cheers,

Carl Fogel

Hello Carl!

When I built my current steel bike, I cold set it on the same jig for
equal measurments on each dropout.  I built it with Campy dropouts
which are the same thickness on the left and right...  That was some
years ago, but I haven't crashed the bike (or backed into it with a
car!) so I assume it is still square.

Dear Jeff,

Sounds reasonable to me.

I see some vague concerns in this thread, but I can't help wondering
if anyone can detect a 3.7 mm axle offset by just riding the bicycle.

Apart from the natural wish to have the damn thing dead center, since
it's brand-new, what would a 3.7 mm offset actually do, assuming that
the wheel spins and the pedals turn without hitting the frame?

Make the bike pull to one side? If so, which side? Increase rolling
resistance? Make it more prone to shimmy?

I'm not arguing, just wondering what the specific expectations are.

Cheers,

Carl Fogel- Hide quoted text -

- Show quoted text -

I think you might find your rear wheel more prone to sliding out when
leaning into a hard corner- I'm not sure, it was a long time ago and
my early wheel builds using a manure truing stand ( centred in the
stand but visbly off in the frame), so it could be something else.
.

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