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Thursday, June 30, 2022

A transition to 1x Drivetrains

 For a couple of years now, I've been hearing a creak and clack on my bicycle whenever I pedaled hard, but would disappear when I stood up. I replaced the chain, and the problem persisted. I looked for a crack in the chainstay, and didn't see any. Then one day at the end of January, I looked at the seat tube, and there it was, a crack around the seat tube just above the front derailleur clamp. I conferred quickly with Carl Strong, shipped the bicycle up to him, and he confirmed that yes, it was the derailleur clamp that cracked the tube, but that there was no way a clamp should have done that. He searched through his records and discovered that the seat tube and top tube were from a defective batch where heat treatment had not happened. He promised to build me a new frame, putting me near the front of the line.

I called around to see who could build me a frame. Rivendell didn't have any frames my size handy, and the closest that came was R&E cycles in Seattle, who could build me a new frame in 6-8 weeks, they thought. Grant loaned me a Charlie Gallop prototype for a week, but he wasn't going to sell me that bike, and while it was a fun enough bike, it wouldn't have been a good substitute for my custom touring bike, though I decided that I would place an order for a Roadini whenever Grant got a new batch in. Having cracked 2 titanium frames I think I can justify having a backup road bike!

Since I had the frame stripped anyway, I decided that now was a good time to try a 1x drivetrain. The problem with 1x12 was that they all needed a new wheel or a new freehub body for my white industries hub. Those xD/xDR drivers for the T11 hubs were not to be found for love or for money, so I gave up on that idea. The NX Eagle 11-50t cassette was one possibility if I wanted 12 speed, it wasn't compared favorably to the Deore groupset. The M5100, however, was available and reasonably priced, if on the heavy side. The Shimano 12-speed MTB groups all require a wider wheel spacing (135-142mm) and so weren't even under consideration. What is surprising is that the 11s MTB cassettes fit onto 10s wheels without any modification --- it turned out that the only reason Shimano introduced 11s road specific groups was because the racers would disdain running any cassette with as big a sprocket as 30t, and with smaller big sprockets the chain would rub against the spokes of a 10s wheel!

I did the analysis on the weight and to my disappointment it would come up to be a wash. Sure, I'd lose the left shifter, 2 chainrings and the front derailleur clamp and cable, but the increased weight of the m5100 11-51 over the 11-36 was 314g, and the total savings of all the other parts was only 340g. Nevertheless, after Pengtoh mentioned how much he disliked his front derailleur, I realized that there were many occasions when I would avoid shifting the front simply because I didn't want to risk dropping the chain, and the few times when I did drop the chain it was annoying.

I ordered the m5100 cassette 11-51, the m5100 SGS rear derailleur, an ultegra 11s chain, and a microshift 11-speed MTB bar-end shifter. You need the MTB specific bar-end because Shimano increased the pull ratio of the 11 speed MTB rear derailleurs, so my old 10-speed silver shifters wouldn't be able to shift the whole range of gears. I eschewed getting even a barrel adjuster because experience has taught me that the way I ride and the places I ride will simply get the indexing out of adjustment faster than I can keep it adjusted. I considered getting the DiaCompe 11-speed downtube shifter, but when I mentioned that to Carl, he thought that a braze-on on the thinnest part of the downtube wasn't a good idea, so I stuck with a bar-end shifter. I also got new bar tape. I also splurged and got the RX810 GRX crank, since I wanted to save the triple for the Roadini, which did have downtube shifter bosses for my Silver downtube shifters. In retrospect, I should have just ordered a Wolf-Tooth 38t chainring for the Ultegra triple, since after trying the 1x for a few weeks I cannot imagine going back to a triple chainring setup.

It took 2 months for Carl to deliver me a new frame, and I got very bored riding my MTB everywhere, though I did find a few interesting trails around my neighborhood to tide me over. When the frame arrived, I put it together, learning the hard way that it's easy to put together the 11s cassette's 11t sprocket in wrong. Then I learned the hard way what the B-screw was for, and how you have to adjust it carefully or the derailleur would move too close to the cassette in the middle gears and interfere with upshifts! It took a few rides to get the headset/fork all settled in, but once I got it together I quite enjoyed it. There are shifting challenges since I'd gotten used to shifting 10-speed on my triplet and on my previous singles, but a few days with the bike made me realize that I hardly ever used the 13t sprockets on my bikes with multiple chainrings, and that indeed I had frequently stood up and stomped on the pedals to get over steep sections rather than gear down because I didn't really want to bother with the shift to and from the granny --- the extra lower gears don't come into play unless you plan for it and are willing to take the hit because you know it's going to be that steep.

My initial rides with the new low gear were grindy --- in low gear the cage would rub. But after adjusting the B-screw that grind went away and now the bike is quiet in all gears. In the extreme range the chainline definitely looks funny, but so far it's been perfectly functional and quiet. And of course, the bike no longer makes that creak/clack when pedaling hard since the frame isn't cracked! I discovered that it's possible to install the Shimano Ultegra 11s chains wrong --- the logo needs to face away from the bike, and the words are supposed to read right side up on the upper side of the chain. Trust Shimano to make something that used to be idiot-proof something that's easy to get wrong. After 300 miles I fixed the reversal, and to my surprise the drivetrain became more noisy. I had it checked at a local bike shop, and the employee said I did it right. The answer is to stop buying Shimano chains and switch to non-directional chains like KMC and SRAM.

Looking at the gearing, it looked like I could get a Wolf-Tooth 36t chainring for the bike for touring, and get a 19inch gear, which was what I had back when 11-34 cassettes were the norm rather than 11-36. When touring, I'd be restricted to an 88" high gear, but when I toured with Arturo, the only time he missed a 100" high gear was one day in Austria when we had a tailwind and a downhill. I could definitely live with that.

When putting the drivetrain together, I thought the 11-51's top gear would hardly ever gets used: to get to use the 40/11, I'd have to be riding at 30mph at 100rpm. To my surprise, I found myself doing that far more often than I would back when I had a 3x setup --- I simply never thought to shift to the big chainring/small sprocket because it was too much hassle, but when it was easy to just slam the shifter to the small sprocket I'd do it all the time! 

To my surprise, I discovered that I was a little faster over the local climbs than on my triple. What happened was that on the triple, I'd get down to the 39/36 (29" gear), and not bother trying to get to the 24/28, 24/32, or 24/36 unless I was anticipating steep stuff. On the 1x drivetrain, I could go from the 40/39 (28" gear - just slightly lower than the 39/34), and if it got a little steeper I'd just shift down to the 40/45 or even 40/51 on dirt before bottoming out. I took the bike over all the steepest local hills I could find: Montebello RoadBohlman-On-Orbit Bohlman, Black Road, and Rapley trail. Sure, my low wasn't as low as the 24/36, but making the shifts convenient and not risking chain drops meant that I actually used more of those gears. As usual, the engineer in me got confounded by the human factors, which turn out to be much more important than numbers on a spreadsheet. And all this despite lots of studies showing the 1x has more drivetrain friction/drag than 2x or 3x, because of the extreme chain angles in lower gears! It turns out that running a 24t chainring is much less efficient than a 40t chainring, and I bet that means the actual frictional drag difference is a wash for someone who was running their 3x drivetrains out of spec anyway (officially, Shimano would only have supported 30/39/52 on my Ultegra SL). As usual, the default Shimano gearing works only if you're a strong 25 year old but wouldn't work at all for anyone else. This default position explains why SRAM has been steadily gaining market share --- the 1x setups are actually far better and more easily customizable for only moderately strong cyclists.

I think left to my own devices I probably wouldn't have switched to a 1x gearing, but now that I have it I can see why it's taken off --- with 11 speeds at the back and a wide enough range, there's no need to put up with the additional issues of having a front chainring or derailleur. During this testing period I did an aggressive ride with Bowen on the tandem and dropped the chain no less than 3 times despite having a chain watcher installed. The unreliability of triples definitely means that I will do my best to ride only 1x from now on. This is one of those technologies that the tourists will adopt long before the racers will do so. In fact, I think I should consider it on the triplet, where a chain drop is very disruptive (and it's hard to coordinate easing off on the pedals when shifting), and I care even less about the high end! When I build up my backup road bike this summer I anticipate going all in on 1x as well. That's how good it is! All in all, I think the 1x11 and 1x12 are good enough to justify the expenditure and hassle to switch over.

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