Would 1x10 make sense in the mountains, or at Moab, where the terrain is steep and traction amazing compared to our snotty clay? Probably not. But then, it's not like I get to ride in those locations often. Also, I'm pretty strong rider and can usually power through stuff without shifting, where most riders need to shift. Provided I can cover the gearing extremes for my usual riding, all the extra ratios should be unnecessary.
Choosing the right ratios
Stock 2x10 gearing was 26/38T rings and 11-36T cassette. The extreme ratios for these numbers are 1:0.72 - 1:3.45. Most of my riding was in the 38T ring and 19-24T cogs, for a range of 1.58-2. Taking the average, my most common ratio is 1:1.79.
Replacing the front with a single 32T ring and keeping the cassette the same would give me a range of 1:0.88 - 1:2.9, with the middle ratio being 1:1.89. For a 34T ring, the range is 1:0.94 - 1:3.09, with middle 1:2.01. Given I usually ride higher gears, a 34T was tempting. But since many people reported good results with a 30T, I settled on the 32T as a compromise. It'll give gearing only slightly taller than my most commonly used 2x10 ratios.
Wide-narrow rings are the secret
These are not your mother's chainrings. To ensure your chain stays on the ring without the safety of a front derailleur, the teeth are designed with an alternating wide/narrow pattern that completely fills the corresponding holes in your chain. The teeth are also taller to reduce the chances of bounce-off. The RaceFace (104mm BCD) was highly rated and a bargain at about $45 from Jensen.
Below you can see the size difference between 26T, 32T and 38T.
Ideally, the chain line should be centered with your cassette. I used a couple of spacers to nudge the ring inwards of the middle position on the spider. I also shortened the chain by about 4-6 links to reduce chain slap. Look at all the stuff that came off!
A quick ride down the street suggests everything works perfectly and the ratios are in the right ballpark. Hopefully the gearing proves not too short (or tall) for riding at Kingdom Trails in a couple of weekends. Already I prefer the setup because it completely eliminates the risks of hitting the derailleur with the swing arm, or nasty chain suck. The more open space means easier maintenance when the clay starts flingin'.
Look at that extra ground clearance!
Thanks to my riding buddy "Skid" Marc Labonte for sharing his thoughts on his own conversion to a 1x10 setup.
Update: Just gave it a good trail workout and can say this is an AWESOME setup. Bike feels more planted, maybe because there's absolutely no chain slap or noise like you'd hear with a front derailleur. The larger teeth and smaller ring probably also contribute to the sense of a better connection to the back wheel. Gear ratios are good too: no problems tackling a few steep (but short) climbs or picking up some speed on long downhills. The simplification of having one less thing to fuss with (front shifting) also seems to let me focus more on riding. This was definitely a good good upgrade to the Tallboy.
Update 2: After a long weekend of riding at Kingdom Trails (including some DH at Burke Mountain) and a punishing steep technical ride in Gatineau Park (well beyond the limits of traction in places), I can say there are absolutely no shortcomings with the gearing. Bike runs cleaner, quieter, and more reliably across the full range, in both sandy and muddy conditions, than with a front derailleur. I wouldn't change a thing.