Compact front derailleur on large diameter seat tube

I have a Scott CR1 frame that has a diameter 35mm seat tube. Per Campy specs
the derailleur braze on's mounting slot should be centered 27.2mm from the
middle of the seat tube. It seems odd to me that Campy specs the mounting
slot further away as the diameter of the seat tube get larger, e.i, (seat
tube/mounting slot in mm) 28.6/24.75, 32/26 and 38/27.2. This means that the
derailleur must have more inward travel as the seat tube gets larger in
diameter, since the chainline doesn't change with the diameter of the seat
tube.

My problem is that with a Campy compact front derailleur adjusted to the
maximum inward position will not clear the chain in the last 2 rear cogs.
The chainline is correct.

I don't see any fixes to using a compact crank on this frame other than:
1. Get a new derailleur that moves inward more.
2. Modify the derailleur, grind metal off, so it move more inward.
3. Make a custom brazeon that has the slot more inward by about 2mm.

Anyone else run into this problem?

 

[Qui si parla Campagnolo]

Use a standard front der...

 

Yes thanks for the tip I have one on order from Excel. I hope it works out.


"Tom Kunich" <[email protected]> wrote in message
news:[email protected]...
> <[email protected]> wrote in message
news[email protected]...
> >I have a Scott CR1 frame that has a diameter 35mm seat tube. Per Campy
> >specs
> > the derailleur braze on's mounting slot should be centered 27.2mm from
the
> > middle of the seat tube. It seems odd to me that Campy specs the
mounting
> > slot further away as the diameter of the seat tube get larger, e.i,
(seat
> > tube/mounting slot in mm) 28.6/24.75, 32/26 and 38/27.2. This means that
> > the
> > derailleur must have more inward travel as the seat tube gets larger in
> > diameter, since the chainline doesn't change with the diameter of the
seat
> > tube.
> >
> > My problem is that with a Campy compact front derailleur adjusted to the
> > maximum inward position will not clear the chain in the last 2 rear
cogs.
> > The chainline is correct.
> >
> > I don't see any fixes to using a compact crank on this frame other than:
> > 1. Get a new derailleur that moves inward more.
> > 2. Modify the derailleur, grind metal off, so it move more inward.
> > 3. Make a custom brazeon that has the slot more inward by about 2mm.
> >
> > Anyone else run into this problem?
>
> The IRD Compact front derailleur may work but you'd have to try it out.
>
>

 

I got the IRD and it works!


<[email protected]> wrote in message news:[email protected]...
> Yes thanks for the tip I have one on order from Excel. I hope it works
out.
>
>
> "Tom Kunich" <[email protected]> wrote in message
> news:[email protected]...
> > <[email protected]> wrote in message
> news[email protected]...
> > >I have a Scott CR1 frame that has a diameter 35mm seat tube. Per Campy
> > >specs
> > > the derailleur braze on's mounting slot should be centered 27.2mm from
> the
> > > middle of the seat tube. It seems odd to me that Campy specs the
> mounting
> > > slot further away as the diameter of the seat tube get larger, e.i,
> (seat
> > > tube/mounting slot in mm) 28.6/24.75, 32/26 and 38/27.2. This means
that
> > > the
> > > derailleur must have more inward travel as the seat tube gets larger
in
> > > diameter, since the chainline doesn't change with the diameter of the
> seat
> > > tube.
> > >
> > > My problem is that with a Campy compact front derailleur adjusted to
the
> > > maximum inward position will not clear the chain in the last 2 rear
> cogs.
> > > The chainline is correct.
> > >
> > > I don't see any fixes to using a compact crank on this frame other
than:
> > > 1. Get a new derailleur that moves inward more.
> > > 2. Modify the derailleur, grind metal off, so it move more inward.
> > > 3. Make a custom brazeon that has the slot more inward by about 2mm.
> > >
> > > Anyone else run into this problem?
> >
> > The IRD Compact front derailleur may work but you'd have to try it out.
> >
> >
>
>

 

I second thought the IRD didn't work after road testing. The derailleur
wouldn't mount low enough so the chain derailed when shifting to the big
ring. Also the spring tension is too high and self shifted back toward the
little ring.

I finally bit the bullet and modified the Campy record derailleur by taking
metal off a pivots point to increase travel and sanding down the inside of
the cage for more clearance.


<[email protected]> wrote in message news:[email protected]...
> I got the IRD and it works!
>
>
> <[email protected]> wrote in message
news:[email protected]...
> > Yes thanks for the tip I have one on order from Excel. I hope it works
> out.
> >
> >
> > "Tom Kunich" <[email protected]> wrote in message
> > news:[email protected]...
> > > <[email protected]> wrote in message
> > news[email protected]...
> > > >I have a Scott CR1 frame that has a diameter 35mm seat tube. Per
Campy
> > > >specs
> > > > the derailleur braze on's mounting slot should be centered 27.2mm
from
> > the
> > > > middle of the seat tube. It seems odd to me that Campy specs the
> > mounting
> > > > slot further away as the diameter of the seat tube get larger, e.i,
> > (seat
> > > > tube/mounting slot in mm) 28.6/24.75, 32/26 and 38/27.2. This means
> that
> > > > the
> > > > derailleur must have more inward travel as the seat tube gets larger
> in
> > > > diameter, since the chainline doesn't change with the diameter of
the
> > seat
> > > > tube.
> > > >
> > > > My problem is that with a Campy compact front derailleur adjusted to
> the
> > > > maximum inward position will not clear the chain in the last 2 rear
> > cogs.
> > > > The chainline is correct.
> > > >
> > > > I don't see any fixes to using a compact crank on this frame other
> than:
> > > > 1. Get a new derailleur that moves inward more.
> > > > 2. Modify the derailleur, grind metal off, so it move more inward.
> > > > 3. Make a custom brazeon that has the slot more inward by about 2mm.
> > > >
> > > > Anyone else run into this problem?
> > >
> > > The IRD Compact front derailleur may work but you'd have to try it
out.
> > >
> > >
> >
> >
>
>