Originally Posted by
base2
I built an CS-RK3 into a 622 rim with 42mm tires on to. I installed a 11 speed 11-42 cassette because mountain 11 fits on a road 10 speed free hub. I installed a 42 tooth chainring so as to maintain a 1:1 drive ratio. The derailleur was a Shimano mountain M8000/9000 shifted with Road 11 speed shifters and aTanPan to translate road/mountain pull ratios.
The package resulted in a range of 21-146 gear inches & 680% range. I mostly cruised in 3rd/overdrive in the 24-32 tooth cogs at 16-22mph. The hub worked perfectly fine.
I've since moved that wheel set to Mrs. Base2's Salsa Marrakesh and installed 622x32 tires. 20.5-138 gear inches. She doesn't ride terribly fast, but the tall gearing allows her, her preferred 60-70 cadence with out being in the fast wearing 11, 12, 13 end of the cassette.
Hypothetically, on a 20 inch 406, with 50mm tire you'd have 15-102 gear inches with out exceeding 1:1 which is that hubs actual limit any way. A derailleur that is long enough to accommodate a 42 tooth big cog has it's own concerns with ground clearance. 1:1 gets you your 15gi low no matter what chainring & big cog you choose as long as they are equal tooth counts. All you need to do then is decide how big of a chainring nets you the top speed you want and choose ring and cassette range accordingly.
I like the RK3 and am seriously considering building another wheel set so I have another of my very own.
My only complaint, if you can call it that is the freehub engagement is a function of the ratio selected. (Underdrive/direct/overdrive) This is magnified by the cog selected. Meaning if you are coasting in overdrive in a big cog you may need to turn the crank set as much as a ⅓ to ½ revolution to engage the pawls to drive the wheel. This is not really an issue in direct or under drive or towards the small end of the cassette. It's hardly a problem. Just a source of minor irritation, sometimes.
FWIW: I'm used to fast engaging free hubs and I tend towards faster than the utility/recreational cycling end of the spectrum. So, I may be hypersensitive to very wide range cassettes and hub engagement speed. IOW: YMMV.
thanks for sharing your real word experience!
glad to know the SA hub can handle the 15 gear inch low as that was my main concern. It also does provide nice ground clearance while offering a very wide range so it may well be a great setup for small wheeled bikes.
Although as Ron points out this comes with a weight penalty and the entire range may not be used often.
Still I think I may try it in one of our bikes (have been tasked with building up 4 touring folders for the family!)