rear derailleur size
12-09-21, 03:35 PM
#26
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I thought the topic is simpler and closer to "pure arithmetic":
Calculate N1=Nr teeth largest ring + Nr teeth large cog - nr. teeth smallest ring - nr teeth smallest cog.
Compare N1 with N2 (N2 = max. deraileur capacity - nr. of teeth).
If N1>N2, it does not work.
If N1=N2 or N1<N2, it works.
If you have 2 alternatives that work (N1<=N2) - say medium and long, then:
The medium will give faster shifting (although the difference might be too small to feel it) and might be noisier when close to "big - big". The large should have opposite behavior.
Weight difference also exists... surely too small to feel it.
One more point: if you want to alternate 2 cassettes, one for flat roads and another for climbing (bigger cogs), then I think you should consider only Large (to fit both) and dimension it for the largest cassette. Another limitation should be the maximum number of cog teeths accepted by the combination of derailleur and hanger length.
Calculate N1=Nr teeth largest ring + Nr teeth large cog - nr. teeth smallest ring - nr teeth smallest cog.
Compare N1 with N2 (N2 = max. deraileur capacity - nr. of teeth).
If N1>N2, it does not work.
If N1=N2 or N1<N2, it works.
If you have 2 alternatives that work (N1<=N2) - say medium and long, then:
The medium will give faster shifting (although the difference might be too small to feel it) and might be noisier when close to "big - big". The large should have opposite behavior.
Weight difference also exists... surely too small to feel it.
One more point: if you want to alternate 2 cassettes, one for flat roads and another for climbing (bigger cogs), then I think you should consider only Large (to fit both) and dimension it for the largest cassette. Another limitation should be the maximum number of cog teeths accepted by the combination of derailleur and hanger length.
Last edited by Redbullet; 12-09-21 at 03:39 PM.
12-10-21, 02:26 AM
#27
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these discussion are always complicated by terminology.
I try to use what manufacturers use when defining their stuff and that changes, like modern deraillers designed for compact doubles now list the max difference for the front crank and 1x are different also
Also absolutes are to be avoided (which i did not do in earlier disagreement) it really is case by case, so you need to do your research and not rely on rules of thumb
I have seen deraillers where the short cage and long cage had same max cog and small cog, but a larger chain wrap capacity so the long cage could handle a triple.
That is no common at all any more, with deraillers with longer cages being different so they can handle handling bigger max rear cogs in addition to the larger chain wrap (example is the ultegra 8000 derailer for a 34 tooth max cog is different from the, GS (medium cage) that can do 32.
sorta of of topic but if anyone is pushing specs (Shimano is known to be conservative, Campy less so) chain length helps, and IME the best chain sizing is small/small to get the max change and best chance for smooth ops when pushing limits
https://www.youtube.com/watch?v=QuhHn7HaZcQ
I try to use what manufacturers use when defining their stuff and that changes, like modern deraillers designed for compact doubles now list the max difference for the front crank and 1x are different also
Also absolutes are to be avoided (which i did not do in earlier disagreement) it really is case by case, so you need to do your research and not rely on rules of thumb
I have seen deraillers where the short cage and long cage had same max cog and small cog, but a larger chain wrap capacity so the long cage could handle a triple.
That is no common at all any more, with deraillers with longer cages being different so they can handle handling bigger max rear cogs in addition to the larger chain wrap (example is the ultegra 8000 derailer for a 34 tooth max cog is different from the, GS (medium cage) that can do 32.
sorta of of topic but if anyone is pushing specs (Shimano is known to be conservative, Campy less so) chain length helps, and IME the best chain sizing is small/small to get the max change and best chance for smooth ops when pushing limits
https://www.youtube.com/watch?v=QuhHn7HaZcQ
12-10-21, 07:46 AM
#28
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In terms of wrap capacity needed A crankset with 22/36 rings is the same as a 36/50. Both are a 14t difference.
