Rear Derailer for 9-speed Campy Set-up Questions

[johnkjos]

Hi All,

I'm converting from a 9-speed triple Campy set-up to a compact crank set-up. I just bought a Campy Record crankset today. I think I need to replace my long cage rear derailer with a medium cage unit. I am wondering if I can also use a short cage unit (have 13-26 cogs). I assume the shifting would be a bit crisper if I can use the short cage. Is there any offsetting impact?

John Kjos

[thwart]

Don't think you would absolutely have to switch RD's if you're going to switch from a triple to a compact, but your shifting may improve with a shorter cage. Only benefit to a medium cage over a short cage is it leaves open the option of running a larger than 26 cog in the future, if that is pertinent.

In my experience there is little difference in shifting quality between a short and medium cage Campy RD. Although I should add that impression is based mostly on 10 speed drivetrains...

Your triple FD will likely work OK in the new set-up, although you'll have to lower its position to match the slightly smaller big ring.

[johnkjos]

Thanks for your input. I think you helped me previously when I asked about using a 10-speed compact crankset with a 9-speed shifter group. I think I'll try to find the medium cage lenght RD so I have the furure option of using larger cogs.

[palincss]

Hi All,

I'm converting from a 9-speed triple Campy set-up to a compact crank set-up. I just bought a Campy Record crankset today. I think I need to replace my long cage rear derailer with a medium cage unit.


Why? What reason do you have for believing your existing derailleur wouldn't work with whatever cassette you wish to use?

[Dave]

The shifting occurs at the top pulley area, not the lower one, so shifting precision will not be improved with a shorter cage. Apparently some peole think that you can't transmit power until the lower pulley swings back and takes up chain slack. That is not the case.

With 9 speed there are differences between 2001 RDs and shifters and those made prior to 2001. If you mix them, shifting won't be perfect. The older RDs have the B screw in the traditional location, while the newer models have a screw that's hidden under the main pivot. The older RDs require more cable pull than the newer model, to produce the same movement. Literature I have says the average cable pull from the old shifters is 3.2mm and the newer ones is only 3.0mm. That's about the same difference as 9 to 10 speed, since 10 speed shifters pull an average of 2.8mm per shift. I have measured the 10 speed cable pull myself, but don't have either 9 speed shifter, so I can verify those numbers.

The shifting from an older RD can be improved by eliminating some of the axial play at the main pivot, where the RD bolts to the frame. I fixed my old Chorus medium cage RD by making my own shim washer from some aluminum sheet stock (from Home Depot) and installing it behind the c-clip that holds the mounting bolt and spring assembly in place. To figure out how much shim is needed, insert feeler gages behind the c-clip and make a washer that will produce .004 inch or less of axial play. I managed to use one that was .031 inch thick. While you have the RD apart, clean the pivot area and regrease it. I'm using this older medium cage RD with 11 speed and it shifts just fine.

[oldpotatoe]

Hi All,

I'm converting from a 9-speed triple Campy set-up to a compact crank set-up. I just bought a Campy Record crankset today. I think I need to replace my long cage rear derailer with a medium cage unit. I am wondering if I can also use a short cage unit (have 13-26 cogs). I assume the shifting would be a bit crisper if I can use the short cage. Is there any offsetting impact?

John Kjos

No reason to change the rear derailleur. You can use a long cage with a compact, no problem and I doubt you could tell any shifting difference between long-medium or short cage RDers.

[johnkjos]

Thnk you all for the responses and assistance offered with respect to my RD questions. I don't have the experience to install shims, but will take the RD to my local Serotta dealer (Bicycle Ranch in Scottsdale, AZ) if shifting is not precise with my current long cage RD.

Also, thanks for not pointing out that my use of the the term "derailer" should have been spelled "derailleur". Lesson learned.

[Louis]

Also, thanks for not pointing out that my use of the the term "derailer" should have been spelled "derailleur". Lesson learned.


Or "dérailleur" if you want to be snooty ;)

[John M]

You can use the long cage RD. Only real difference between the long and the others is that you will need a longer chain. I guarantee that you will not notice any difference in shifting smoothness--I know this from experience using a long-cage Campy RD with triple and double and cassettes from 13-29 to 12-23. A non-functional difference is that on really rough roads, the longer chain will bounce around more when in the small chainring/smaller cog combos than if you had a short cage RD and commensurately shorter chain.

If however, your RD is pre-2001 (may be based on your post in the classifieds,) then you do need a new RD to go with your new 10s shifters. Most people don't have the wherewithall to do the shimming/modifying that Dave does. If you do get a new RD, look for a mid-cage or long cage to use with your compact crankset. It gives more flexibility with cassette choices than a short cage.

[AndrewS]

As pointed out, your current derailleur will work fine.

It should also be pointed out that cage length (on it's own) has nothing to do with cog size. A short cage and long cage rear derailleur of the same design will shift up onto a 30 tooth cog with equal precision.

The cage length merely determines what the total difference in chain wrap for the whole drive train can be, known as capacity. That is; the combination of largest cogs (53+26) minus the smallest cogs (12+39). The greater the difference, the larger capacity rear derailleur needed and the longer the cage.

The upshot of that is that you don't need a long cage rear derailleur, even with a triple, if you avoid shifting into the extreme crossover gear combinations (which you shouldn't, anyway). If you avoid those gears you reduce the needed capacity of the rear derailleur and can use a shorter cage if you wish.

I've used short cage Shimano road derailleurs for the past 20 years on mountain bikes with compact triple cranks and 12-28 cassettes. Why? Chain rides higher, under more tension and it's a little lighter. It used to be such a common practice that the DX and XT derailleurs had short cage options.

So use whatever derailleur your heart desires. The one you already own is the cheapest option.