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Sora to Ultegra rear derailleur(7 posts)

Sora to Ultegra rear derailleurGFocker
Nov 20, 2003 9:53 AM
My rain bike has an 8-speed Shimano Sora set up. I have an extra 9-speed Ultegra rear derailleur. In order to use it, what is the minimum amount of parts that need replaced (my wheels will accommodate a 9-speed cassette)?

(I'm thinking, shifters, cassette & chain)

Thanks for the help.
Maybe I'm missing something here...Lone Gunman
Nov 20, 2003 5:01 PM
The deraileur does not care if you have 8 or 9 speed in the rear, but the shifters do. You could put the Ultegra on the rear and adjust the limit screws for the 8 speed and all should work fine.
Wouldn't the spacing be a problem?GFocker
Nov 21, 2003 8:45 AM
I can always try that. Thanks
Lone Gunman is correct...BenR
Nov 21, 2003 3:16 PM
You should be able to use your ultegra 8/9 speed derailleur with no problems. Other than dropping some weigth and achieving a quicker shift to smaller cogs (due to stronger springs), you won't see a big performance difference. I use a modern 8/9 speed ultegra derailleur with 8 speed 600 (ultegra) downtube shifters with no problems. It shifts quicker and more accurately than any vintage of shimano STI, with the exception of 8 and 9 speed dura-ace.

To see a big performance increase with your Ultegra derailleur, you would have to upgrade shifters as well, which would then require a 9 speed chain and cassette, unless you found 8 speed shifters which are hard to find and probably not worth spending money on.

Here's the general shimano history: When going from 7 to 8 speed, they basically re-made the rear hub wide enough to stick another cog on. I don't think the spacing between the cogs changed much, if at all (someone chime in here), which is why the same chain is used for 7 and 8 speed but a different derailleur was needed due to the wider movement range. They may have redesigned the parallelogram, but I don't know for sure. 8 speed didn't last very long (with the exception of low end gruppos) because Shimano quickly figured out how to cram another cog on the new 8 speed hub. Thus, 9 speed uses the same derailleur and hub, but needs a narrower chain due to the tighter spacing. This is also why you can't use 9 speed shifters with an 8 speed cassette. Due to the different spacing, you will be able to dial in on one cog and then the shifting will become progressively inaccurate with each cog farther away.

Also beware of mixing 8 speed and older dura ace derailleurs with shifters from other component levels and vice versa. Older Dura-Ace used a different parallelogram and cable pull length. The cassettes themselves have the same spacing between cogs(I think). This isn't a problem with 9 speed parts.
Thanks for the thorough answer! (nm)GFocker
Nov 21, 2003 3:27 PM
OK, but-Chen2
Nov 21, 2003 3:36 PM
"a different derailleur was needed due to the wider movement range."

I don't mean to contradict you but when I converted a friends 7-speed RSX STI to 9-speed I decided to try it with the old derailleurs which, to my surprise, worked perfectly and have for two years with no adjustments. This bike now has 9-speed 105 shifters, Ultegra 12-27 cassette and chain, 105 rear hub, RSX derailleurs, triple crank-set, rings, and BB. It shifts as well as any triple I've ever seen.
I stand corrected, thanks!..BenR
Nov 24, 2003 8:20 PM
that's what I thought I was told by the LBS (who I know longer do business with due to honesty issues) but never had reason to try it myself. I can see the motive behind the claim by him or his Shimano rep since it would sell more derailleurs.