front shifting woes - braze-on issue?

Kyle.B.H said:

In the two years I've had my bike, the front shifting (shimano STI triple),
has never been great. The major problem has been that the front derailer
bottoms out against the seat tube before it can push the chain onto the
granny. And while I've had success getting it to work, the adjustment is
_extremely_ sensitive, such that when I make any sort of drivetrain change,
it can be a nightmare to get working properly again.

My question is - is this likely an issue with my braze-on? This is a
hand-made frame, so could it be that the braze-on is not allowing the proper
distance between f.der and seat tube? I've tried two different deailers
with the same result. I could go with a wider bottom bracket, but that
would mess up my chainline. Is there a 'standard' for the seat tube to
derailer (say, the mounting bolt) distance?

I'm seriously considering removing the braze-on so that I can use a clamp-on
front derailer. I'm sure an hour or so with my hacksaw and dremel would
take care of it nicely, albiet leaving a nasty scar on my beautiful frame.

Any tips? I've considered going to friction or Campy front shifting, but if
the derailer can't move in far enough, those solutions won't help.

Thanks,

Kyle

Shimano triple chain line spec is 45mm +/-1.5mm. If yours is less,
then a longer spindle is a good idea and should help reduce the
problem.

Shimano spec for the lateral distance between the bike's center plane
and the center of the braze-on slot is somewhere around 25mm. This is
from memory, so might be +/- a millimeter or so.

But braze-on position doesn't sound like the issue; you say the
derailleur hits the seat tube. Moving the braze-on won't move the seat
tube out of the way. ;-)

Considered filing the derailleur? You might be able to get another
millimeter or two of travel.

Considered asking the builder to add a careful dent on the seat tube?
Many new bikes come with intentional dents from the factory.

Kyle.B.H said:

In the two years I've had my bike, the front shifting (shimano STI triple),
has never been great. The major problem has been that the front derailer
bottoms out against the seat tube before it can push the chain onto the
granny. And while I've had success getting it to work, the adjustment is
_extremely_ sensitive, such that when I make any sort of drivetrain change,
it can be a nightmare to get working properly again.

My question is - is this likely an issue with my braze-on?

-snip-

Quoted message said:

Any tips? I've considered going to friction or Campy front shifting, but if
the derailer can't move in far enough, those solutions won't help.

That's a regular situation with Shimnao fronts. Campagnolo
fronts have a different issue- the anchor hits the frame
when you shift to high gear.

It is really tough to remove material as the spring mount is
what hits. A slight chainline adjustment, adding a 2mm
spacer under the right cup, may help. Changing to bolted
format won't help. I'm no fan of braze fronts but that isn't
the cause of this.

It's sometimes possible to judiciously bend the cage such
that the outer plate hits the chain sooner at a point toward
the rear of the cage. An experienced mechanic can do that
quickly.
--
Andrew Muzi
www.yellowjersey.org
Open every day since 1 April, 1971

none-<< The major problem has been that the front derailer
bottoms out against the seat tube before it can push the chain onto the
granny. >><BR><BR>
<< My question is - is this likely an issue with my braze-on? >><BR><BR>

Issue with the seattube width/BB shell placement.

Try a spacer under the right BB cup, a 'small' dent in the seattube, a
grindaway on the front der where it hits the seattube.

Peter Chisholm
Vecchio's Bicicletteria
1833 Pearl St.
Boulder, CO, 80302
(303)440-3535
http://www.vecchios.com
"Ruote convenzionali costruite eccezionalmente bene"