Follow up derailleur question
 

The Rd on my roadie is original (19 yrs) and has a few issues. Pivots are worn, tension spring is slack, shifting is somewhat erratic especially on inclines. Rear sprocket is a 6 speed with some wear as well. My intent is to go with a 7 speed mega range fw and change the derailleur. A friend has a couple of gently used Rd's. An Ultegra 65 or 6600 short cage and long cage. Are they good choices? I can get a set of seven speed down tube shifters as needed. The Deore has also been mentioned as a decent replacement. Additionally is there any advantage using a short vs a long caged Rd? Thanks for all the help as I am a total noob! Lp

Your choice of long chage s short cage is dictated by total wrap capacity... if for instance your front chainrings were 30 and 52 you would have a 22 tooth difference, and similarly a 11-34 rear cassettee has a 23 tooth difference, The total wrap capacity required in the RD would then be 45 tooth. it would also need the max and min cog capacity to match the rear casette sprockets ie handle a 11 t and a 34 t.

Typically Ultegra (and most other Road RDs max out around 29 t max ( shimano says 25t nax) .... so would not work with your 34t bail out gear, even if they had adequate wrap capacity.

Go to the Nashbar site and take a look at some different RD's select the "spec" tab for each of them and you will get the idea pretty quick of what will and wont work for your set up

Shimano Tourney long cage is what I use with the megarange. At $14.99 and reliable I like it. It always shifts well unless you bend it.

OK the tooth count numbers and chain wrap lingo are making sense now. Another Rd question. Will a nine speed Rd work with a six or seven speed system if the tooth count and wrap are within specs? And can the H and L limits be adjusted for the six or seven speed shifters? Ya'll be patient with the noob. thanks Lp

There's functionally no real difference between a 6 speed RD and a 9 speed RD. If it can't be adjusted with the stock ones you could probably get longer screws.

Thats what I was thinking ---- thanks. Lp

It's all about 'lateral swing'. As long as the 9 sp derailieur can cover the distance from the smallest to the largest cog in the cluster 'laterally' you'll have no probs whether it's 5-6-7-8 or 9 cogs. Derailleurs themselves have no 'indexing', but do have limits to the distance they can travel horizontally. For example, you can use a 7 speed derailleur to cover a 9 cog cluster provided it has the swing distance required.

Currently, I'm using a Shimano Sora 8/9 speed derailleur rated at 27t limit on a 12x28 8 sp cluster. It BARELY makes it as the 'B' screw adjustment is cranked all the way, but it makes it and that's all that matters to me. The H/L limitscrews are set in normal positions and the system works fine. I've got a single 48t frt w/bar-end shifter.

In answer to your 2nd question as long as there's no indexing involved. The H/L limit screws are just there to stop the chain from falling off either end. Downtube, stem and Bar-end shifting are functionally the same, ie they're all friction/cable systems. Obviously, the quality varies afa smoothness, etc goes, but they're all pretty much the same technologically speaking.

OK I'm confused again. The current Rd is an indexed 6sp worn out Shimano Exage. How does indexing come into play whether the Rd is a 6 vs 9 speed? Lp

As long as they are all Shimano or Shimano index compatible rear derailleurs (with the sole exception of Dura Ace prior to 9-speed) the number of "speeds" is determined by the shifter and the derailleur just goes where the shifter sends it.

Thanks for the clarification. Lp