Originally Posted by
oldbobcat
Alf, thought you would have known that cage length has nothing to do with the maximum rear cog capacity--it's the maximum distance between the axle and the jockey pulley, which is a function of the length of the derailleur body, the length and shape of the hanger, and the offset of the jockey pulley from its pivot on the knuckle. Anyway, the point is moot, it's a short cage with a nominal max cog of 26t.
As maydog mentioned, you might get it to clear a 30. I'm more conservative and I hate pulley rumble, so I'll say you should be able to push the 2300 to 28t.
Anyway, the cheapest workaround, and a pretty damned elegant one to boot, is a new Shimano Claris rear derailleur (RD-2400). It's spec'ed to handle a 32t max rear cog and 37t total wrap, exactly what you're aiming for. Your local bike shop should be able to get you one for around $37 US, or less. A more economical substitute is the SunRace RD-R81 rear derailleur, advertised as a direct substitute for the Claris. You might be able to find these online.
Should you decide you need 1:1 gearing with a 34t cassette, any Shimano MTB rear derailleur made for 8- or 9-speed chains will do the trick. For an appropriate mix of performance (shifting precision), weight, durability, appearance, and price, I recommend the new 9-speed Alivio (RD-430) and Acera (RD-390) units.
And as alfeng mentioned, you will need a longer 8-speed chain.
Originally Posted by
Volnix
Thanks
Since the 28t cassette is allready beyond the specifications of the derailleur it's probably the maximum I might try and maybe a new chain. Hope that the derailleur wont brake and damage the wheel spokes. One LBS allready told me half a year ago that the chain is allready a bit streched and should be replaced...
As for a more extensive upgrade I might check some campagnolo stuff online, but e-shopping is starting to give me a headache lately, tracking the orders and stuff, so I would prefer to get them for a local shop for 2 euro more or something, but they dont sell them...
Might put the current stuff on sale too, just in case I can get some Campagnolo or Sram 10 speed shifters of the net...
@maydog
the climbs are kinda steep. The problem is that, in no way I can climb them with a near 90rpm cadence. It was like weightlifting on the last time I tried! So I am usually just doing some flat rides or some very easy climbs.
OH!?! There ARE a lot of things which I don't know ...
BUT, the limitations of Shimano (
and, I suppose Campagnolo to a lesser extent) rear derailleurs is probably NOT one of them ...
I guess that I need to make
a sweeping generalization based on a limited, but meaningful (
in my mind!?!) observation of various derailleurs & derailleur hangers ...
The Cog Size which is spec'd by Shimano & Campagnolo is based on the old 70s-80s derailleur hanger as seen on my OLMO ...
You will observe the minimal
drop because the derailleur hanger was designed for the Campagnolo Nuovo Record & OTHER vertical rear derailleurs which preceded the Japanese takeover of the component market.
As you may-or-may-not recall, the largest Cog which was spec'd for a Nuovo Record rear derailleur was (
also) a
26t Cog.
BUT WAIT. I was able to a Nuovo Record rear derailleur with a 13-28 Freewheel because my Peugeot's derailleur hanger was MUCH LONGER. No, it wasn't ideal ... not even close, but it was usable with "rumble" only with the 42t Chainring (
?) & 24t Cog (
?!?) combination (
due to the orientation of the cage & how the Upper Pulley wheel was situated) but NOT when the chain was on the 28t Cog (
again, due to the orientation of the cage ...).
The Nuovo Record's greater limitation (IMO) was the
lack of chain wrap because I had paired the 13-28 Freewheel with an XT front crank when I used THAT Crank/Freewheel combination for one ride when I was trying to determine how low a gear I
needed ...
BUT, the slack chain was a
cosmetic issue
BUT, despite the Olmo's minimal hanger drop, you should also observe that it is a Shimano 105 (
RD-5600) rear derailleur whose design I "
corrected" by replacing the 11t UPPER Pulley Wheel with a 10t Pulley Wheel.
That might be an 11-32 Cassette (
who can remember?!?) ... but, maybe that's an 11-34 because I know that at the moment the Olmo has an 11-34 Cassette ... for the record, I reverted to using an (
older) XTR rear derailleur on the Olmo.
OTHER people made the observation that they have successfully used a Shimano Road rear derailleur with an 11-32 Cassette by
adjusting the B-screw to provide more clearance for the Upper Pulley wheel so that the 11t Pulley Wheel does
not have to be replaced.
At some point, I modified an Ultegra rear derailleur with the cage from an XT rear derailleur (
kids, don't try this at home!) because I thought it would be nice to have a little more chain wrap just in case I was going to wuss out with a 50-34 crankset ...
And, here is a 12-34 Cassette with a "
corrected" Dura Ace rear derailleur ...
Yes, that chain is
too short for that Cassette!
!!
Further ...
It must have been about 10 years ago that I re-stacked a 12-25 (?) Cassette for a friend with a 28t Cog. The bike (
Giant CADEX) had a "normal" rear derailleur hanger ... although the DA (
7400) rear derailleur was
/is spec'd to 26t, there was no problem ... and, the chain was JUST long enough that it didn't need to be changed.
In other words (
the point of all of the preceding verbiage), the max Cog size is a VERY CONSERVATIVE specification for Shimano's rear derailleurs ...
And so (
again, based on the FUJI Sportif 2.3 C being capable of handling the combination of a 50-34 Crankset + 11-32 Cassette) ... trying the existing rear derailleur, first, is a realistic & more economical path to try.
BTW. The previously mentioned CAMPAGNOLO Veloce shifters are from a "real" brick-and-mortar bike shop which apparently sells its excess inventory on eBay.