help: front derailleur adjustment - compact crank

I am having allot of difficulty with the front derailleur setup for my
new compact crank. The chain will rub the outer plate (right side) of
the front derailleur when it's in the small or big ring up front and in
the middle (!) of the rear cassette.

I had the bike shop adjust the derailleur twice and I did so once
myself. I am at the point of scratching my head what to do next. It's
very frustrating.

The bike setup is a 50/34 crank, Ultegra 9sp (6500) front derailleur,
STI shifters and a 12x27 9-speed cluster in the rear. The derailleur
cables are new and the rear shifting is perfect.

It's a Nashbar labeled compact crank made by "RPM" which is the same
Taiwanese company that makes FSA cranks as far as I can tell from doing
some research on the web. I have a 68x108mm ISIS bottom bracket
installed and the q-factor is spec'd at 160mm.

The front derailleur limit screws seemed to be setup correctly; shifting
to and from the rings is fine. The number of usable gears is very
limited though. For instance the 3 or 4 smallest cogs are off limits
while in the small ring due to too much chain-n-derailleur grind.
Trimming wont help. One notable item is that the cable tension must be
set real high. This is more so than I've had to do with past bike
setups. While riding the bike, shifting from big to low or low to big,
I would always have to trim the front derailleur.
This is so even when the chain is in the middle of the rear cassette.

After putting a few miles on the bike, eventually trimming the shifter
would not be enough. I'd still get the grinding noise even while the
chain is residing in the middle of the cogset. Retightening the cable
tension helped alleviate this problem only temporarily and the cable
clamp torque is definitely adequate.

Any suggestions as to what I can do? I wish for the day I could ride in
peace. I'd rather be grinding coffee at the moment instead of my
derailleur. Thanks for your help!

I am having allot of difficulty with the front derailleur setup for my new
compact crank. The chain will rub the outer plate (right side) of the
front derailleur when it's in the small or big ring up front and in the
middle (!) of the rear cassette.

I had the bike shop adjust the derailleur twice and I did so once myself.
I am at the point of scratching my head what to do next. It's very
frustrating.

The bike setup is a 50/34 crank, Ultegra 9sp (6500) front derailleur, STI
shifters and a 12x27 9-speed cluster in the rear. The derailleur cables
are new and the rear shifting is perfect.

Could be that your front derailleur is actually too low (too close to the
chainrings). Try moving it up just a bit and see if that helps.

The front derailleur limit screws seemed to be setup correctly; shifting
to and from the rings is fine. The number of usable gears is very limited
though. For instance the 3 or 4 smallest cogs are off limits while in the
small ring due to too much chain-n-derailleur grind. Trimming wont help.
One notable item is that the cable tension must be set real high.

Too-high cable tension is nearly always a sign of a misadjusted front
derailleur (on a Shimano STI system). If the tension is too high, you're
unable to "trim" the large chainring. If you are able to trim it, then the
tension probably isn't too high.

I just checked my own bike (a Trek 5900 with FSA carbon 50/34 front, D/A
front derailleur and 12/27 rear), and notice that the trailing end of the
front derailleur is just slightly inward (toward the frame) compared to the
front. This is a slightly-different position than you'd set up normally, but
it works very nicely on my bike.

--Mike-- Chain Reaction Bicycles
www.ChainReactionBicycles.com


"Sir, It's Just Me" nospam?@thanks?.? wrote in message
m...
I am having allot of difficulty with the front derailleur setup for my new
compact crank. The chain will rub the outer plate (right side) of the
front derailleur when it's in the small or big ring up front and in the
middle (!) of the rear cassette.

I had the bike shop adjust the derailleur twice and I did so once myself.
I am at the point of scratching my head what to do next. It's very
frustrating.

The bike setup is a 50/34 crank, Ultegra 9sp (6500) front derailleur, STI
shifters and a 12x27 9-speed cluster in the rear. The derailleur cables
are new and the rear shifting is perfect.

It's a Nashbar labeled compact crank made by "RPM" which is the same
Taiwanese company that makes FSA cranks as far as I can tell from doing
some research on the web. I have a 68x108mm ISIS bottom bracket installed
and the q-factor is spec'd at 160mm.

The front derailleur limit screws seemed to be setup correctly; shifting
to and from the rings is fine. The number of usable gears is very limited
though. For instance the 3 or 4 smallest cogs are off limits while in the
small ring due to too much chain-n-derailleur grind. Trimming wont help.
One notable item is that the cable tension must be set real high. This is
more so than I've had to do with past bike setups. While riding the bike,
shifting from big to low or low to big, I would always have to trim the
front derailleur.
This is so even when the chain is in the middle of the rear cassette.

After putting a few miles on the bike, eventually trimming the shifter
would not be enough. I'd still get the grinding noise even while the
chain is residing in the middle of the cogset. Retightening the cable
tension helped alleviate this problem only temporarily and the cable clamp
torque is definitely adequate.

Any suggestions as to what I can do? I wish for the day I could ride in
peace. I'd rather be grinding coffee at the moment instead of my
derailleur. Thanks for your help!

Sir, It's Just Me wrote:
I am having allot of difficulty with the front derailleur setup for my
new compact crank. The chain will rub the outer plate (right side) of
the front derailleur when it's in the small or big ring up front and in
the middle (!) of the rear cassette.

The bike setup is a 50/34 crank, Ultegra 9sp (6500) front derailleur,
STI shifters and a 12x27 9-speed cluster in the rear. The derailleur
cables are new and the rear shifting is perfect.

What chain? I was told that a 9-spd Sram would "work" with Campy
10-spd, and I had the same rubbing. I went to a "real" 10-spd chain (a
nickel-plated Wippermann). With no further adjustments, I now don't rub
until the last cog.

Read the follow-up for M.J. (busy shop owner who rides a compact crank
with short chain stays) and others as well.

richard wrote:
What chain? I was told that a 9-spd Sram would "work" with Campy
10-spd, and I had the same rubbing.

It's a 9-spd SRAM as well, but for a 9 speed setup. The rubbbing occurs
in more than the last cog, too.


Read the follow-up for M.J. (busy shop owner who rides a compact crank
with short chain stays) and others as well.

Ok, I will. Thanks!

Thanks for the reply, Mike.

Mike Jacoubowsky wrote:

Could be that your front derailleur is actually too low (too close to the
chainrings). Try moving it up just a bit and see if that helps.

Ok, I'll give that a try. It's currently about 2mm above.



Too-high cable tension is nearly always a sign of a misadjusted front
derailleur (on a Shimano STI system). If the tension is too high, you're
unable to "trim" the large chainring. If you are able to trim it, then the
tension probably isn't too high.


I'll recheck the cable tension and turn it down a notch. Just out of
curiosity, how do you trim using D/A shifter? For instance, I'm able to
do such with the Ultegra because the right shifter is designed for a
double or a triple ring setup; D/A has two respective 9 spd models.

I just checked my own bike (a Trek 5900 with FSA carbon 50/34 front, D/A
front derailleur and 12/27 rear), and notice that the trailing end of the
front derailleur is just slightly inward (toward the frame) compared to the
front. This is a slightly-different position than you'd set up normally, but
it works very nicely on my bike.

I'd give that a try but it looks like I don't have any leeway space in
the front and between the outer plate and the chain to give.

My intuition is telling me it may be a chainline problem. How would I
know is that's the case?

Sir, It's Just Me wrote:

Mike Jacoubowsky wrote:

Whoops, looks like my newsgroup writer threaded the wrong needle. The
reply s/b to Mike.

I am having allot of difficulty with the front derailleur setup for my new
compact crank. The chain will rub the outer plate (right side) of the
front derailleur when it's in the small or big ring up front and in the
middle (!) of the rear cassette.

Could be that your front derailleur is actually too low (too close to the
chainrings). Try moving it up just a bit and see if that helps.

Ok, I'll give that a try. It's currently about 2mm above.

2mm is normally a pretty good distance. When I see issues it's usually
because somebody has the derailleur almost sitting on top of the largest
chainring.


Too-high cable tension is nearly always a sign of a misadjusted front
derailleur (on a Shimano STI system). If the tension is too high, you're
unable to "trim" the large chainring. If you are able to trim it, then
the tension probably isn't too high.


I'll recheck the cable tension and turn it down a notch. Just out of
curiosity, how do you trim using D/A shifter? For instance, I'm able to
do such with the Ultegra because the right shifter is designed for a
double or a triple ring setup; D/A has two respective 9 spd models.

Not sure what the issue is here; the DuraAce and Ultegra (when used as a
double) shifters both have trim, or centering capabilities. If you don't
have two distinct positions for the large chainring, then you're definitely
running the cable too tight. OR... (read on to next remark)

I just checked my own bike (a Trek 5900 with FSA carbon 50/34 front, D/A
front derailleur and 12/27 rear), and notice that the trailing end of the
front derailleur is just slightly inward (toward the frame) compared to
the front. This is a slightly-different position than you'd set up
normally, but it works very nicely on my bike.

I'd give that a try but it looks like I don't have any leeway space in the
front and between the outer plate and the chain to give.

Could be that the crankset in question doesn't allow for enough room between
the chainring and crank arm. There's quite a bit of room on the FSA carbon,
so there's nho problem with clearance. Sounds like your particular crank may
be a bit too tight there, which is fine for reducing the infamous "Q factor"
but most definitely creates shifting issues.

My intuition is telling me it may be a chainline problem. How would I
know is that's the case?

Run a straight edge between the two front chainrings, and see where it falls
on the cassette. It should never ever fall inboard of the middle of the rear
cassette; that would imply that the crankset is too far inboard, rendering
quite a few small-front-chainring combos useless. Perfectly centered is OK,
although common practice now is to offset outboard (towards the smaller rear
cogs) so that you can use most, if not all of your rear cogs when on the
small chainring.

But there's another type of alignment issue that's rarely discussed. An
out-of-plane bottom bracket (one that's not perpendicular to the frame) can
cause all manner of shifting problems. It's not seen too often, but it
occurs more often than it's diagnosed, and rarely (if ever) checked for at
the factory on less-expensive bikes. Why? Because it's generally not
correctable; the frame has to be tossed.

--Mike-- Chain Reaction Bicycles
www.ChainReactionBicycles.com