nashbar compact crank

On Sun, 31 Jul 2005 17:13:28 GMT, "Sir, It's Just Me"

nospam?@thanks?.? said:

Every time I shift between the small and big rings it requires some
trimming action to get the shifting just right. This is so even if the
chain is currently in the middle of my 12x27 9speed cassette with a nice
chain line.

Quoted message said:

Is there anything else I can do other than get a new compact crank
setup? (And yes, I'd like to stick with STI; no downtube shifters for me.)

I think your problem is common for any compact crank used with a
standard shifter and front derailleur. At least I have the same
complaint. The standard shifter and derailleur are designed for 15
tooth max capacity for optimum shifting. So they work perfectly with
the usual 53-39 rings, only a 14 tooth span, for which they are
designed. The compact 50-34 rings comprise a 16 tooth jump, and the
ultegra shifter and ultegra derailleur don't handle it well. Which is
why IRD now sells a compact specific front derailleur :
http://interlocracing.com/cdfrtder.html

In my case, I was running 9 speed dura ace shifters with ultegra
derailleurs (front and back) and was able, after some fiddling with
limits and tension, to get decent but not perfect shifting in front.
Then a few weeks ago, my right shifter broke, and I decided to upgrade
to 10 speed shifters. I found it hard if not impossible to buy a
right shifter only, and since the dura ace pair was too pricey, I
bought ultegra.

Although my left dura ace shifter was working fine, and forgetting the
truism "if it ain't broke, don't fix it," I installed the new ultegra
shifters front and back. Bad decision. No amount of adjusting and
tweaking would get the ultegra front shifter to move the derailleur up
from 34 to 50 with any degree of acceptability. So I put the dura ace
back on, and it just seems to pull more cable or is more powerful than
the ultegra (hence the price difference?).

I have no clue whether the ultegra front shifter and the IRD compact
front derailleur will be a perfect combo, but $50 for a derailleur
beats $350 for two shifters any day for your particular problem.

While you're at it, check out the IRD compact specific cassettes,
offering an 11-28 span (for both 9 and 10 speeds). Neither shimano
nor SRAM have figured out yet that compact crank users need an 11
tooth cog to keep the from spinning out in the highest gear, as well
as a big cog for super low. The only other choice is Harris Cyclery
"High and Wide" cassette, 11-28, but 9 speed only.

Sir said:

Quoted message said:

Mike Yankee wrote:
Nothing wrong with your crank per se.

The first thing that occurred to me was that you have the wrong BB
spindle length, but you say your chainline is OK so that's not it.

Thanks for the reply. I'm afraid I was not clear enough in my original
message. I think my chainline may be the problem. Here's why. I have
no trouble moving the chain from the small chain ring to the large chain
ring and vice versa.

The problem is after I shift the front derailler, I then have to trim it
to move the front derailleur further out to prevent the chain from
rubbing the front derailler's outter plate.

I suspect the start position is wrong then. You should be able to move
the front der and chain to the big ring and have clearance when on the
smallest cog. Then shifting up the cogset will require you trim the
front der to prevent rub, while still being in the big ring(the trim
function of the lever), then when going to the small ring, you should
have no rub as you go to the biggest cogs.

Quoted message said:

This is always true when shifting to the large chain ring. While moving
the chain to the lower chain ring, I must trim the fron derailluer if
the chain is positioned in a cog other than the 27,24, or 21.

I'm using the bottom bracket recommended by Nashbar, their BB spec'd at
68x108mm. This is the narrowest bb spindle length they offer. That
said, my guess is given my shifting behavoir, it is too wide.

I'm not 100% sure; does this seem reasonable? Again the issue is with
rubbing of the outer front derailler plate.

Quoted message said:

My second thought is that you need to lower the front derailleur a few
mm (closer clearance to your smaller big ring) and, while you're at it,
double-check its other variables (parallel to chainline, inner and out
stops, cable tension).

I tried that already. This crank replaced an Ultegra crank retrofitted
with a 50 tooth chain ring. The other items you mentioned have been
reviewed, too.

Thanks again for the reply.