I’ve been running SRAM and Shimano 10sp wide-range cassettes for almost a year now with road shifters, as well as having installed them on a number of custom bikes. They work pretty well. In fact, my SRAM Red shifters/X.9 mtn rear derailleur/XT 11-34 cassette shifts with crisp perfection. I don’t have really strong preferences for SRAM vs Shimano cassettes, and I’ve installed SRAM, Wipperman, and Shimano 10sp chains. But there are certain recipes for shifters and derailleurs.
SRAM Double-Tap shifters (Red, Force, etc): for 11-32 cassettes, you can use either the longer cage Apex derailleur (which is nice and inexpensive), or any of the 10sp mtn rear derailleurs. The Apex rear derailleur is rated for a 32T cog and might not work for cassettes bigger with cogs bigger than that (eg, 11-36). In my experience, you can’t often cheat the max cog rating of a SRAM derailleur. Better to go with the 10sp mtn derailleur. Make sure you choose a cage length with enough chain wrap capacity to deal with the combined ranges of the chainrings and cogset. Also, SRAM’s unfortunate nomenclature for mtn components can be confusing. For example, there is a X.9 rear derailleur that is 10sp and several generations of X.9 that are 9sp. Only the 10sp stuff will work.
Shimano STI: for 10sp road cassettes and chains, the best choice is 9sp Shimano mtn rear derailleurs, though older 8sp might be passable. New Shimano 10sp mtn derailleurs are completely INCOMPATIBLE with any road shifters. Also, the Shimano 9sp rear mtn derailleurs seem to be a fairly tolerant of exceeding the rated max cog size (ie, they were never meant to accept cogs bigger than 34T but in practice they’ll work on a 36T with margin to spare). Again watch the chain capacity.
Campagnolo: you’re screwed, thanks for playing. Well, not completely. Campagnolo doesn’t make cassettes with cogs larger than 29T,and Campag 10sp spacing (cog-to-cog) is physically wider with different mounting splines than the Shimano/SRAM standard. And Campagnolo rear derailleurs aren’t meant to work with cogs bigger than 29T….so what part isn’t completely screwed? Here’s some voodoo that I’ve tried. Take Campagnolo 10sp Ergopower shifters, SRAM 10sp mtn rear derailleur, and a SRAM or Shimano 10sp mtn cassette (on a wheel with the Shimano-type splines). It seems all wrong, but if you calculate cable pull for shifters vs cog-to-cog spacing vs derailleur ratios, it works out. Even better, other people like Lennard Zinn have been doing this with SRAM road derailleurs for a few years. Now that the SRAM mtn derailleurs (10sp) have the same ratio as the road derailleurs, this magic mix is even more useful. I’ve installed that on one customers bike so far.
Note: all this info sets aside issues of cranks. front derailleurs, and front shifters. That is a very complex story of integrated systems, shit that sorta works, and then stuff that just doesn’t. The basic rule is don’t mix and match there.
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