compact crank and chain wrap

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In article <[email hidden]>,

anerobic said:

i'm building up a new bike for myself and i got a new compact crankset
with 50/34 rings. i run a 12-27 cassette. so it seems i need a rear
derailleur with a chain wrap capacity of 16+15=31. when i look at the
specs for an ultegra
short cage it's listed as 29 max wrap. anyone running a short cage
with such a set up? can i squeak by or do i need a "triple" long cage
rear. thanks
i don't want to replace the cassette cause it's a dura-ace i got for
cheap. 🙂

_ Sheldon Brown thinks it should work

http://www.sheldonbrown.com/gloss_ca-m.html#capacity

You're only exceeding the very conservative manufacturer's
capacity by two, as long as you avoid small/small you should
be fine.

_ Booker C. Bense

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On one bike I have a 34-48 compact on the front and a 12-27 cassette
in the rear with a DA double rear derailleur. This shifts perfectly
on that bike. On the other bike I run a 34-48 compact on the front
and a 12-30 cassette in the rear with a DA double rear derailleur.
This configuration rubs a bit on the front derailleur when in the 34
ring in the front and 30 cog in the rear combo. But I like the really
low gear without having a triple or mt components. I am trying this
combo for the first time and it might need a bit more adjust to work
smoothly.

anerobic <[email hidden]> wrote in message news:<[email hidden]>...

Quoted message said:

i'm building up a new bike for myself and i got a new compact crankset
with 50/34 rings. i run a 12-27 cassette. so it seems i need a rear
derailleur with a chain wrap capacity of 16+15=31. when i look at the
specs for an ultegra
short cage it's listed as 29 max wrap. anyone running a short cage
with such a set up? can i squeak by or do i need a "triple" long cage
rear. thanks
i don't want to replace the cassette cause it's a dura-ace i got for
cheap. 🙂

anerobic said:

i'm building up a new bike for myself and i got a new compact crankset
with 50/34 rings. i run a 12-27 cassette. so it seems i need a rear
derailleur with a chain wrap capacity of 16+15=31. when i look at the
specs for an ultegra
short cage it's listed as 29 max wrap.

You should be OK. However, you might want to think about a tighter
cassette the next time you replace it. That is one of the advantages of a
compact crank, you still get decently low gears without gaps.

--

David L. Johnson

__o | "What am I on? I'm on my bike, six hours a day, busting my ass.
_`\(,_ | What are you on?" --Lance Armstrong
(_)/ (_) |

anerobic said:

i'm building up a new bike for myself and i got a new compact crankset
with 50/34 rings. i run a 12-27 cassette. so it seems i need a rear
derailleur with a chain wrap capacity of 16+15=31. when i look at the
specs for an ultegra
short cage it's listed as 29 max wrap. anyone running a short cage
with such a set up? can i squeak by or do i need a "triple" long cage
rear. thanks
i don't want to replace the cassette cause it's a dura-ace i got for
cheap. 🙂

I'll swap you a DA 12-25 for it. Then you can use a short cage RD. 🙂
Keep kicking myself for not buying another 12-27 DA cassette when you
could get them for $54 at Performance. Now they're unavailable or
$100+. Oh well, you shouldn't have trouble with hills once you get it
working.

--
Mark Wolfe Lakeside, ca http://www.wolfenet.org
gpg fingerprint = 42B6 EFEB 5414 AA18 01B7 64AC EF46 F7E6 82F6 8C71
Pretty, smart, sane: Pick two.
- Ron Echeverri

I replaced a DA 53/39 crank with an FSA 50/34. I have a DA short cage
derailleur. I use both a 12-25 and a 12-27 rear cassette and it works
just fine with the FSA compact crank.

anerobic said:

i'm building up a new bike for myself and i got a new compact crankset with 50/34 rings. i run a 12-27 cassette. so it seems i need a rear derailleur with a chain wrap capacity of 16+15=31. when i look at the specs for an ultegra
short cage it's listed as 29 max wrap. anyone running a short cage with such a set up? can i squeak by or do i need a "triple" long cage rear. thanks
i don't want to replace the cassette cause it's a dura-ace i got for cheap. 🙂

I run 50x34 and 12-30 with Dura-ace short cage rear der. with rated capacity of 29. You gotta size the chain exactly right and don't use the small-small or big-big combos.

anerobic-<< i'm building up a new bike for myself and i got a new compact
crankset
with 50/34 rings. i run a 12-27 cassette. so it seems i need a rear
derailleur with a chain wrap capacity of 16+15=31. when i look at the
specs for an ultegra
short cage it's listed as 29 max wrap. >><BR><BR>

Don't worry about the numbers.
If a 53/39 and a 12-27 needs a short cage, smaller rings certainly will work
also.

You 'may' need to take a link outta the chain otherwise it will work fine. We
do this conversion all the time w/o changing the rear der.

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

Gonzo-<< I run 50x34 and 12-30 with Dura-ace short cage rear der. with rated
capacity of 29. You gotta size the chain exactly right and don't use
the small-small or big-big combos. >><BR><BR>

Not true, you can use a short cage rear der, a compact crank and a big cogset
and still use the small/small w/o droopy chain and the big/big w/o breaking a
chain...this ain't brain science...

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

In article <[email hidden]>,

(Qui si parla Campagnolo ) said:

this ain't brain science...

Or even rocket surgery ;-)

--
Shane Stanley

[email hidden] (Qui si parla Campagnolo ) wrote in message news:<[email hidden]>...

Quoted message said:

Don't worry about the numbers.
If a 53/39 and a 12-27 needs a short cage, smaller rings certainly will work
also.

You 'may' need to take a link outta the chain otherwise it will work fine. We
do this conversion all the time w/o changing the rear der.

I would suggest the best (secret weapon) is the "long-er" cage Dura
Ace rear deraileur. It should be able to take anything you will throw
at it. Too bad I wasn't in a buying mood when they were $46. That's is
below dirt cheap for a best of breed deraileur.