Front derailure shifting function factors

Gary Jacobson said:

I'm not talking about adjustment here.

What are the factors of design that contribute to poor shifting with a 46-34 front set up?

Seems that "overshifting' is an ongoing problem with me set up. 73 degree seat tube. TA
chainrings. 105 double, and Campy record triple FDerailures. Chain gets hung up on and then falls
off to the outside of big chainring. Back off the travel and then no shift to big ring.

I just bought a Sachs microdrive FD. If this a possible solution? Why? What is it about a
microdrive FD that could make it work better than the other two FD's I have tried ?

Can I modify the standard FDs to work?

Don't really "understand" front shifting issues. Seems straight forward, but apparently is not.

A compact cage is shaped with a tighter radius for usually a 46 or a 44 outer. That will work
better than a full size cage for your purposes as it can be set at a good height. That height is
usually about 1-2mm above the chainring at the closest point. Adjusting that correctly puts the
chain in the meatiest part of the cage during a shift. Also get the cage aligned in the plane of
the chainrings when viewed from above. A dramatic loss of shift quality will ensue if that's even a
few degrees off.

--
Andrew Muzi www.yellowjersey.org Open every day since 1 April, 1971

Quoted message said:

Seems that "overshifting' is an ongoing problem with me set up. 73 degree seat tube. TA
chainrings. 105 double, and Campy record triple FDerailures. Chain gets hung up on and then falls
off to the outside of big chainring. Back off the travel and then no shift to big ring.

I just bought a Sachs microdrive FD. If this a possible solution? Why?

What

Quoted message said:

is it about a microdrive FD that could make it work better than the other two FD's I have tried ?

Assuming you're running a friction shifting setup for the front derailleur-

The Microdrive FD should work much better than the Campy because its curvature will better match
that of the chainring. Right now you're running a front derailleur that, when mounted high enough to
clear the large chainring, has a tail end (the part pointing towards the rear of the bike) that's
hanging high in the air, because the chainring's radius is considerably smaller than what its
designed for.

Another possible problem would be if the 46t chainring you're using is designed to be used as
something other than the outside position.

--Mike-- Chain Reaction Bicycles chainreactionbicycles.comchainreactionbicycles.comOpen ↗

"Gary Jacobson" <[email hidden]> wrote in message
"]news:[email hidden]...

Quoted message said:

I'm not talking about adjustment here.

What are the factors of design that contribute to poor shifting with a

46-34

Quoted message said:

front set up?

Seems that "overshifting' is an ongoing problem with me set up. 73 degree seat tube. TA
chainrings. 105 double, and Campy record triple FDerailures. Chain gets hung up on and then falls
off to the outside of big chainring. Back off the travel and then no shift to big ring.

I just bought a Sachs microdrive FD. If this a possible solution? Why?

What

Quoted message said:

is it about a microdrive FD that could make it work better than the other two FD's I have tried ?

Can I modify the standard FDs to work?

Don't really "understand" front shifting issues. Seems straight forward,

but

Quoted message said:

apparently is not.

Thanks.

Gary Jacobson Rosendale, NY

Gary Jacobson said:

Don't really "understand" front shifting issues. Seems straight forward, but apparently is not.

Put your bike in a stand with the front derailleur in the 2nd ring. Use the shifter and move it to
the big ring position without moving the cranks. Then, slowly turn the crank and you'll see how the
front derailleur climbs up the inner plate and mounts the chain on the larger ring.

At the outset the lower part of the inner plate pushes the chain toward the larger ring and the
shape of the inner plate raises the chain. When the chain gets near the top of the big ring, the
upper part of the front derailleur ticks the chain onto the teeth.

The shape and length of the inner plate is designed for rings within a certain range.

For 46/34 a Shimano XTR 900 front derailleur is best. That is a pre-microdrive front derailleur. I
have no idea if it works with indexed STI.