front derailleur placement for compact cranks?

jim-<< This is a question for those of you who have sucessfully converted to
compact cranksets. Did you have to lower the front derailleur? If so,
by how much? >><BR><BR>

Mount the front der the same distance from the big ring as on a bigger ring.
Same distances, same orientation, just lower. Usually with a brazeon, you can
get it low enough but if not, a few minutes with a file and you can make the
slot lower.

If on a clamp on and the bottle boss is in the way, take a little metal off the
clamp, make a little 1/2 circle to accomodate the boss

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

[email hidden] (Jim A) wrote in message news:<[email hidden]>...

Quoted message said:

Hi Folks,

This is a question for those of you who have sucessfully converted to
compact cranksets. Did you have to lower the front derailleur?

Depends on the size of the outer chainring on the 110 mm bcd crankset
compared to the size of the outer chainring on the curent crankset.

If so,

Quoted message said:

by how much?

Depends on the size of the outer chainring on the 110 mm bcd crankset
compared to the size of the outer chainring on the curent crankset.

If you have a braze-on derailleur, how did you remedy the

Quoted message said:

adjustment?

The size of the outer chainring on the 110 mm bcd crankset compared to
the size of the outer chainring on the curent crankset will determine
if you need a remedy. If going from a current 53 tooth chainring to a
50 tooth chianring on the 110 mm bcd crankset, then the brazeon will
have enough adjustment. If not the small gap between the front
derailleur outer cage and the chainring won't make any difference.

Quoted message said:

I'm asking because I have a bottle boss about 3mm below my derailleur
clamp and I'm afraid that if I convert to ta compact crankset I won't
be able to adequately reposition the front derailleur, if necessary.

Why are you asking about front derailleur brazeons if you have a clamp
on front derailleur? 3 mm of downward adjustment will be good enough
if you change from a 53 to a 50 tooth chainring. And a 48 outer ring
will work just fine too. I've run a crankset with about 1/2 inch of
space between the front derailleur outer cage and the chainring and it
shifted just fine.

Quoted message said:

Thanks,
Jim Andreyo

(Jim A) said:

Hi Folks,

This is a question for those of you who have sucessfully converted to
compact cranksets. Did you have to lower the front derailleur? If so,
by how much? If you have a braze-on derailleur, how did you remedy the
adjustment?

I'm asking because I have a bottle boss about 3mm below my derailleur
clamp and I'm afraid that if I convert to ta compact crankset I won't
be able to adequately reposition the front derailleur, if necessary.

Thanks,
Jim Andreyo

The radius of the chain ring changes by 2mm per tooth. If changing
from 53 to 50, then you will probably lower the front derailleur about
6mm.

I'd consider filing the band to clear the bottle boss.

That said, many folks have reported acceptable operation with a
substantial gap.