Originally Posted by
Andrew R Stewart
One concern regarding cog count is that with increasing cog numbers the large one often gets close to the spokes. The older, freewheel assumed, ders can have rather thick cage plates, pulleys that are wide and can catch on the spokes if not careful. If someone needs to ask questions about basic der capacities they might not be aware of the cage/spoke clearance issue until too late. Andy.
Very good point; the wide range of motion can get you across all eight cogs, but it can also get you in trouble!
As usual, one question can and should lead to another, but to answer the original question, "Which of these RDs will work across 8 cogs?" The answer is "All of them, Katie!" (most likely)
YMMV, spacing of the cogs the cogs, spacing of the hub, thickness of the dropout, how the RD is hung all make a difference.