Originally Posted by sydney
First, your undertaning is somewhat flawed or poorly understood.And that is not because it was poorly articulated on my part. There are short cage mtb RD that do shift big cogs. Also, there are old RD that shift big cogs because old freewheels with 33 and 34 cogs were fairly common, and there were even old 38 tooth freewheels... Secondly, that cage length business is the common misconception you get about long cage RDs, and it comes not just form LBS guys that should know better.... Duno how many times I have said it, but cage length is about wrap capacity, not big cog, which is in the parallelogram design. All one has to do is look at current shimano shimano road RD specs. The big cog capability is the same for both long and short cage.That's cuz the parallelograms are identical. The 27 tooth spec is conservative tho and most will shift a 30 and sometimes, depending on the application, one can get away with a 32 with them.If it was me and I wanted to use a 32 or bigger cog, I'd just go with a mtb RD, unless I had a road type just lying around and didn't mind spending some time fiddling with it. Campy spec does not tend to be as conservative and one can get away with less with them...A Shimano mtb RD is different in that in order to clear the bigger cogs involved, it tracks a steeper angle as it traverses the cassette, and that applies wether it is a long or short cage model.
Actually I think you are saying the same thing but I think you're arguing from the opposite way. I mentioned you specifically because you have indeed repeated it so many times, and it finally sunk in, through all of the layers of smoke.
Let's review. I said:
Originally Posted by 'nother
That is to say: a short-cage derailer will not generally handle a 32 or 34T cog . . . however, not necessarily because of the cage length, but because of the length of the parallelogram/arms.
Now, I'll grant that you can pick on the first part of this as being inaccurate, since there are indeed short-cage derailers that will handle 32+, but to evaluate the entire statement on the basis of that phrase alone is to take it out of context improperly. The bit I've emboldened above is the important part, and I don't think that's in any way contradictory to what you've said, or to reality.
However, relative to Sheldon's article, what I'm referring to is the part that says:
Long-cage derailers have greater takeup capacity, and work with all types of cassettes.
Which to me is a bit misleading, based on my understanding and first-hand experience, which is: simply being "long-cage" does not mean a RD will handle any cassette (e.g. any cog size, which is what I assume Sheldon means when he says "all types of cassettes").
I do not think my understanding is flawed as you proclaim, but please feel free to correct as necessary.