Compact cranks

RJ Peterson said:

I just bought a compact crank and am wondering if it will work with standard
(short cage) road rear and front derailleurs? The crank has 50/34 teeth --
it will replace a 50/39 setup.

Thanks

Rear derailleurs are rated by capacity. Capacity equaling the
difference between the smallest and largest cassette cogs PLUS the
difference between largest and smallest chainrings. Pretend you have a
13-26 cassette and 50-34 chainrings. That is 13-26=13 PLUS 50-34=16.
Total equals 29. Short cage rear derailleurs are rated at roughly 27
capacity. Medium cage at roughly 30. Long cage roughly at 36.
Roughly meaning you can add 2-3 or so to these rough numbers and be
perfectly fine. If you exceed the capacity of the derailleur the chain
will droop in the small chainring-smallest 2-3 or so cog combinations.
Usually not a problem since you don't use these gears much. But if you
were using your 50-34 crank with a 13-29 cassette, total is 32, and a
short cage rear derailleur, you would probably have chain droop in your
smallest 3-4 or so cogs. That would be concern because if you use
these gears, and you probably would, the drooping chain could jump the
pulleys and catch on the derailleur cage. Its possible.

RJ Peterson said:

I just bought a compact crank and am wondering if it will work with standard
(short cage) road rear and front derailleurs? The crank has 50/34 teeth --
it will replace a 50/39 setup.

I ran an FSA Energy 50/34 with an 2004 Ultegra short cage and a 12-25
cassette, no problems. I ran the same derailleur with a Ultegra 600
53/39 and a 12-28 cassette, again no problems. Currently using same
derailleur and a Campy 52/42/30 and a 12-25 cassette, I get slight
chain rub on the rear derailleur cage when in the 30 (front) 12 (rear)
combo, so really no problems. This whole short cage/long cage is
completely overrated. In my experience short cage works for up to 28
teeth in the back, over that use an MTB GS.

-Nate

On Mon, 30 Jan 2006 14:03:05 -0600, "RJ Peterson" <[email hidden]>

Quoted message said:

I just bought a compact crank and am wondering if it will work with standard
(short cage) road rear and front derailleurs? The crank has 50/34 teeth --
it will replace a 50/39 setup.

You won't have any problem in back. The front might possibly be a
problem, as most front derailleurs aren't really designed for the 16
tooth jump. I had an Ultegra 9 speed which I couldn't get to shift
smoothly and quickly. So I swapped it with an old Dura Ace 8 speed
off my circa 1990's bike and no problem. On my new build, I installed
a IRD compact specific front derailleur, but I really think the Dura
Ace worked better.

P.S. Think about installing a chain checker/keeper and take 2 links
out of your 53/39 chain

Doug Taylor said:

On Mon, 30 Jan 2006 14:03:05 -0600, "RJ Peterson" <[email hidden]>

Quoted message said:

I just bought a compact crank and am wondering if it will work with standard
(short cage) road rear and front derailleurs? The crank has 50/34 teeth --
it will replace a 50/39 setup.

You won't have any problem in back. The front might possibly be a
problem, as most front derailleurs aren't really designed for the 16
tooth jump. I had an Ultegra 9 speed which I couldn't get to shift
smoothly and quickly. So I swapped it with an old Dura Ace 8 speed
off my circa 1990's bike and no problem. On my new build, I installed
a IRD compact specific front derailleur, but I really think the Dura
Ace worked better.

P.S. Think about installing a chain checker/keeper and take 2 links
out of your 53/39 chain

Don't just take the links out, without checking. Going from a 50 to a
50, there should be no reason to change chain length.

Life is Good!
Jeff

On Mon, 30 Jan 2006 14:03:05 -0600, "RJ Peterson" <[email hidden]>

Quoted message said:

I just bought a compact crank and am wondering if it will work with standard
(short cage) road rear and front derailleurs? The crank has 50/34 teeth --
it will replace a 50/39 setup.

Depends on which front derailleur you have. Some do a much better job
than others.

Doug Taylor said:

The front might possibly be a
problem, as most front derailleurs aren't really designed for the 16
tooth jump. I had an Ultegra 9 speed which I couldn't get to shift
smoothly and quickly. So I swapped it with an old Dura Ace 8 speed
off my circa 1990's bike and no problem. On my new build, I installed
a IRD compact specific front derailleur, but I really think the Dura
Ace worked better.

My exact experience, The DA FD 77?? works expecially well. The IRD
compact is a lost cause. It does nothing well. Stiff springs and set
too high for a braze on fitting and you must use an adapter for a
clamp. Currrent Campy fronts work fine too.

Doug Taylor said:

You won't have any problem in back. The front might possibly be a
problem, as most front derailleurs aren't really designed for the 16
tooth jump. I had an Ultegra 9 speed which I couldn't get to shift
smoothly and quickly.

So strange! I have the same (Ultegra 9v) and replacing 53-39 with FSA
50-34 works perfectly.

Sure, I should adjust it, since with 53-39 can work even not perfectly
aligned, while with 50-34 requires a perfect setup.

I mean, I placed chain on 53/13 (my hardest gear) then I aligned derailer
with *chain*, not with crank. Then I reduced clearances to minimum.
Finally I adjusted cable tension to have a proper trim-click, even if
with my setup I don't need trimming at all.

Cheers.

--
Massimo Bacilieri AKA Crononauta
ICQ:4005815

RJ Peterson said:

I just bought a compact crank and am wondering if it will work with standard
(short cage) road rear and front derailleurs? The crank has 50/34 teeth --
it will replace a 50/39 setup.

Thanks

Yes it will, just lower your front der, perhaps take one link out of
your chain(depends on how ell it was sized before) and go ride.

Paul Kopit said:

On Mon, 30 Jan 2006 14:03:05 -0600, "RJ Peterson" <[email hidden]>

Quoted message said:

I just bought a compact crank and am wondering if it will work with standard
(short cage) road rear and front derailleurs? The crank has 50/34 teeth --
it will replace a 50/39 setup.

Depends on which front derailleur you have. Some do a much better job
than others.

We have tried some of the 'compact front ders, both IRD and Campag and
find the standard front derailleur for a double works the best for all
compact systems. A chain watcher and ....wait for
it....................Robert is your father's brother.

On Tue, 31 Jan 2006 04:34:45 GMT, Jeff Starr <[email hidden]>

Quoted message said:

Quoted message said:

P.S. Think about installing a chain checker/keeper and take 2 links
out of your 53/39 chain

Don't just take the links out, without checking. Going from a 50 to a
50, there should be no reason to change chain length.

You mean 53 to 50. Surely he should check, but my experience was the
chain was slack without removing the links. Of course, better to have
it too long than too short.
http://sheldonbrown.com/derailer-adjustment.html#chain

Qui si parla Campagnolo said:

We have tried some of the 'compact front ders, both IRD and Campag and
find the standard front derailleur for a double works the best for all
compact systems. A chain watcher and

I believe you are totally correct. I think that they design the
'special' compact front derailleurs to minimize dropping the chain
inside. When I tried a Campy CT that seemed the case. The regular
Campy front works fine. And yes, I use Jump Stops with compact and
triple cranks.

Doug Taylor said:

On Tue, 31 Jan 2006 04:34:45 GMT, Jeff Starr <[email hidden]>

Quoted message said:

Quoted message said:

P.S. Think about installing a chain checker/keeper and take 2 links
out of your 53/39 chain

Don't just take the links out, without checking. Going from a 50 to a
50, there should be no reason to change chain length.

You mean 53 to 50. Surely he should check, but my experience was the
chain was slack without removing the links. Of course, better to have
it too long than too short.
http://sheldonbrown.com/derailer-adjustment.html#chain

Go read the original post. The guy said he had a 50/39. Maybe he
mistyped, or maybe that is what he has. Shimano did have some cranks
that came with 50.

I'm just going by what the OP wrote.

Life is Good!
Jeff

On Wed, 01 Feb 2006 00:58:09 GMT, Jeff Starr <[email hidden]>

Quoted message said:

Quoted message said:

You mean 53 to 50. Surely he should check, but my experience was the
chain was slack without removing the links. Of course, better to have
it too long than too short.
http://sheldonbrown.com/derailer-adjustment.html#chain

Go read the original post. The guy said he had a 50/39. Maybe he
mistyped, or maybe that is what he has. Shimano did have some cranks
that came with 50.

I'm just going by what the OP wrote.

Hmmm. I read right over making the assumption that "just bought"
compact meant that he must have had a 53 before. I am under the
impression that 50 tooth rings are all 110 mm bcd, i.e. compact. If
he already had 110 bcd, he already had compact.

Whatever. My point is that if you are switching from 53/39 to compact
50/34, I advise checking your chain length - I had to shorten mine
because my chain was slack in the "bad" gear ratios of small ring/
smaller cogs.

Doug Taylor said:

On Wed, 01 Feb 2006 00:58:09 GMT, Jeff Starr <[email hidden]>

Quoted message said:

Quoted message said:

You mean 53 to 50. Surely he should check, but my experience was the
chain was slack without removing the links. Of course, better to have
it too long than too short.
http://sheldonbrown.com/derailer-adjustment.html#chain

Go read the original post. The guy said he had a 50/39. Maybe he
mistyped, or maybe that is what he has. Shimano did have some cranks
that came with 50.

I'm just going by what the OP wrote.

Hmmm. I read right over making the assumption that "just bought"
compact meant that he must have had a 53 before. I am under the
impression that 50 tooth rings are all 110 mm bcd, i.e. compact. If
he already had 110 bcd, he already had compact.

I have had a 50/39 on my Record crank for 5 years. 135mm BCD.

Quoted message said:

Whatever. My point is that if you are switching from 53/39 to compact
50/34, I advise checking your chain length - I had to shorten mine
because my chain was slack in the "bad" gear ratios of small ring/
smaller cogs.

Qui si parla Campagnolo said:

Doug Taylor said:

I am under the
impression that 50 tooth rings are all 110 mm bcd, i.e. compact. If
he already had 110 bcd, he already had compact.

Frankly, I'm astounded anyone with an internet connection could make a statement
like this, unless they're profoundly lazy. A trivial google search shows availability
of "130mm 50 tooth chainring". Why waste everyone's time without doing even a few
keystrokes of research to back up your assertion?

Dan

On Wed, 01 Feb 2006 14:39:42 GMT, Dan Connelly

d_j_c_o_n_n_e_l@i_e_e_e.o_r_g said:

Qui si parla Campagnolo said:

Doug Taylor said:

I am under the
impression that 50 tooth rings are all 110 mm bcd, i.e. compact. If
he already had 110 bcd, he already had compact.

Frankly, I'm astounded anyone with an internet connection could make a statement
like this, unless they're profoundly lazy. A trivial google search shows availability
of "130mm 50 tooth chainring". Why waste everyone's time without doing even a few
keystrokes of research to back up your assertion?

I was trying to explain why I misread the original post (thinking he
"meant" 53/39 when he typed 50/39), because of "my impression" that 50
tooth was compact 110 bcd. I didn't do any research. Very generally
speaking, most people "switching" to compact these days are going from
the standard 53/39 to 50/34 or 50/36. Like me and a bunch of my 50+
friends who figured out it was cheaper and "cooler" than going to
triples.

So really, I only have one bad: I misread the original post.

Qui si parla Campagnolo said:

I have had a 50/39 on my Record crank for 5 years. 135mm BCD.

48/36 on my Zeus crank for 20 years. 120mm BCD. Plus ça change, plus c'est
la même chose...

--

John ([email hidden])