Hello everyone,

So, as expected, my trial 1x conversion was a failure; the chain just wouldn't stay put, given that the factory 50t chainring is designed to "throw" the chain rather than retain it. So I put everything back the way it was, and even managed to break a couple of bolts in the process (replacements already on the way.)

With that being said, I liked the bike - and the trigger shifter - far better than I did with its factory 2x10 setup, so I'm looking into going ahead with an actual, permanent 1x setup. A few questions:

1. Can I go wrong with a 42t chainring as a starting point? (50+34) ÷ 2 = 42 was my simple(ton) logic here.

2. My factory FSA Vero spider is 110bcd. The chainrings that I looked at were the FSA Megatooth 110bcd chainring ($75 shipped to my door in Jeddah,) the Wolf Tooth 110bcd Cyclocross (also $75 shipped to my door) and the Hope 5 Bolt 110bcd Retainer Ring ($65 including this set of chainring bolts, shipped to my door.) All of these chainrings feature the alternating narrow/wide tooth design that's supposed to hold the chain down. Can I go wrong with either of these?

3. On which side of the spider should the replacement chainring go? Naturally, aesthetics would dictate that the chainring be bolted to the outer side of the spider, but the mechanics of it all (chainline, etc.) could dictate otherwise...

4. Would it be just better (in terms of fitment and cost) to find and order a complete 1x crankset rather than individual chainrings that may or may not fit the existing FSA Vero spider?

Thanks in advance!

We can't tell you what gear ratio range (and therefore which chainwheel) will work with your unspecified cassette and your particular needs. Neither can we tell you which position on the spider will work without knowing your chainline. In fact neither may be ideal. Think about what gear combinations you used as a 2x10 and look up a gear ratio calculator, then look up info on determining and adjusting chainline before you make any more mistakes, as 1x cranksets designed for fixed/single gear bikes may have a different chainline than you need..

And you're right! So, unless I have ready access to a brick-and-mortar shop that's willing and able to let me try different things and see what works before I buy (which is impossible where I live) - it's all a crap shoot...

Regardless of whether you buy a complete 1x crankset or just a chain ring, a 42t ring might work well, but not because it's the average of your two previous ones. If you need to (and it may be worth doing, to ensure you spend your next money only once), put it back to the 34-50 that it had and go ride your normal routes, looking for particularly fast and slow sections. You want to try to find the gear ratio range that works for you, on average. The shortest ratio (slowest speed) will probably be in your 34t ring. At your slowest, where are you on the cassette? Largest sprocket? Or do you never go that low? Maybe you go only as low as the 3rd largest or 4th largest. Say it's an 18t sprocket (for example). Whatever it is, that's your shortest ratio -- use a gear inches calculator (online) and find the gear inches. Say it's 35. Now figure your tallest ratio. Do you really need a 50-11 ratio? If you're up in the 50t ring, do you go as small as a 13t or a 12t or an 11t on the cassette? Whatever that is, that's your tallest ratio -- use a gear inches calculator to figure it out. Say it's 103.

Now you're armed with the data necessary to find what will suit you the best. If you're keeping your rear cassette, whatever it may be, start playing with gear inch calculators and determine what your range (shortest to tallest) will be with a 38t ring, a 40t ring, a 42t ring, etc. Maybe a 38t ring will give you a range from 32 to 87 (I have no idea what your cassette is, so this is just as an example). Maybe a 40t ring will give you a range from 36 to 93. Maybe a 42t ring will give you a range from 45 to 106.

You can see how, with the cassette kept as a constant, changing your single chain ring will move your range of available ratios up and down. If you find yourself more often using the shorter ratios, then you probably want to consider a smaller chain ring on the front. You'll lose top end, but you'll maintain your climbing gears. If you would rather have the top end and will walk the bike if forced to on a hill, then maybe you want a larger ring.

1x drivetrains are best served by wide ratio cassettes. Many run 42-11 cassettes or 48-11 or even wider. It takes more sprockets to keep the jumps reasonable. Lots to consider.

Good luck and have fun!

Understood. There's nothing particularly favorable about a42t; I just thought it might be a good starting point to see what works in the long run.

With that being said, this is by far my least ridden bike, and it's a far cry from my Dahons. As you said, I need to ride it much more often in its current setup to better understand how I can and should mod it.

If you have a working 2x system you can use it to figure out the gear range you need (assuming that range is somewhere within the existing 2x system), then use that knowledge and a gear calculator to choose a chainring.

I understand all about gear ratios. No problems there. The more immediate issue, however, is one of practical mechanics rather than pure physics: the possibility of getting an actual chainring - with the right bcd and all, and with with money paid - only to find out after it gets here that it won't physically fit onto the existing spider or may work poorly with the rest of the bike for one reason or another. I'm sure you can understand just how big of a bummer that would be when you live halfway around the world from the source.

Another fact to consider is that, if I elect to go for a complete crankset instead, square-taper cranksets (such as this one or this one) are becoming harder to find - which means that I may need to think about swapping out a perfectly good bottom bracket for a more "modern" one for more and better crankset choices. That's both more money I'm able to spend and more involved than I would prefer!

Food for thought.

What brand crank is it? There are a number of BCDs out there, but not THAT many and unless you have a modern crankset you shouldn't have trouble trusting that a ring with the right BCD will fit.

It's an FSA Vero 50/34compact 110bcd - the bike's factory set. No idea about the other, more nerdy aspects of it, such as chainline and Q-factor (pedal face to pedal face, is that it?)

A 42T is an excellent choice-- paired with an 11-42 cassette, you can climb just about any hill you would come across, and the 42-11 spins out around 30mph.
The Vero will fit any traditional 5-bolt 110bcd chainring. Of those three, I would recommend the WolfTooth. They make fantastic parts. Also check out availability of RaceFace-- as good as WolfTooth, might be a little cheaper.
I run my narrow-wide chainring in the outer position on a 110bcd 2X crankset (FSA Gossamer) because I spend more time in the bottom half of the cassette than I do in the top half.
You can find some dedicated 1X cranks fairly cheap, but few in square taper, so you would also need to change the bottom bracket-- not a huge issue, as you'd be looking at a Hollowtech II or MegaExo most likely, either of which can be had for $20-30 (plus the tool to install/remove.)

Great advice. I'm still thinking all this through while I wait for my replacement chainring bolts to get here.

I've seen a few square taper cranksets ranging between 42t up to 50t, from Origin8 at the more affordable end to Sugino at or near the top. That Wolf Tooth chainring indeed looks like a quality product that's not too pricey for being US-made.

With that being said, I'm still not prepared to go all out and swap the bottom bracket out for a more "modern" setup. The limited finances notwithstanding, that does feel like a bridge too far at this point.

I have a 1x11 setup on one of my bikes and like it a lot. I ride mostly smooth surfaces so I thought I was safe from chain drops. After close to 1000 it finally happened in a way that was not easy to resolve on the road without breaking the chain, so I made "the call home". I replaced the generic inner 42t ring with a narrow wide Wolf Tooth and it's been working great. Other options would be a chain saver, running a dummy FD, or installing a clutch RD.

I'm thinking 1x's are the future for a lot of cycling applications.

While it's true that knowing your chainline measurements would be ideal, on most 2x bikes the conversion to 1x will place the chainring closest to the "middle" of where the 50 and 34 are (in your case). If you take a look at pics of the 1x conversion chainrings installed (Wolftooth site is a good reference), you will note that they bolt up to the large chainring position.

I would quibble a bit with that. A 42-11 does not "spin out" at 30mph - that's only about 100rpm.

p.s. I don't see it as progress to go from 15% jumps on a 5 speed freewheel with double chainrings (30+ years ago) to a 15% jump on a 10 speed cassette with a single chainring.

Lots of single chainring cyclocross racing setups over the decades..

Road crank, triple length BB, 42t etc. chain ring on inside,
and a disc chain-guard in place of the outer chainring..

chain minder or a 2nd disc chain-guard on the inside...

I was in the biz for over 20 years, well aware of single ring options. I'm referring to road setups. To each his own, but I can't stomach the look of a 42 tooth cassette cog.

I'd like to see a situation where a person is riding solo, on level-ish ground, spinning a 42-11 in excess of 100rpm. That's not why we do it. On any given ride, I will not exceed 105rpm, and have an average cadence in the 80s. Yeah, Pro Tour guys spin out above 140rpm. We are not those guys.

I'm talking about real-world spinning out. Not a gear calculator, or what the pros do. A typical rider on a typical day stops pedaling at a certain speed/cadence. No free jersey for getting home 2 minutes sooner.

Uh I spin at ~100rpm on flat ground at sweet spot(90-95% FTP) for miles on end solo. When a put road tires on my 1x Superx with a 42T it spins out at a relatively slow speed so 100+rpm is also normal. I use a 34/46 double on my commuter so a 46x11 spins out a relatively low speed also, so I descend at 110+rpm almost every day. In groups guys are spinning out 50x11 at 120 rpms on descents before tucking or coming out of turns. Its not that uncommon

Not all of us ride on flat ground. Sometimes I go downhill too.

Well, when I can get my FTP up over 8W/kg to match yours, I'll think about changing out my 42T. Until then, I will quietly continue to turn ~85rpm in 42/14 on on the flats, which is good for around 21mph. Almost pedestrian, such speeds.

I think you are misunderstanding. A 42T is good for speeds much past 30mph you think so why would you need to change it out? When people talk about spinning out is typically on descents

Wow, did not think my comment would start a storm. It is simply not true that a 42-11 will "spin out" - that is, be unable to be pedaled faster - at 30 mph. Even for a non-racer 120 rpm is not outlandish for a short time. Saying that one does not want to spin faster than 100rpm is not the same thing.

As for pedaling downhill, it has two functions only - getting maximum exercise out of a ride and keeping the legs warm. If one is trying for maximum speed over a given distance (up and down course) it's wasteful to pedal rather than to tuck and coast, because wind resistance at speed makes the incremental cost of a couple miles per hour too high.

At my size, moving on flat ground on 42-11 @ 100rpm would require something on the order of ~700W. This is not a matter of want. This is a matter of can't.

Wow, did not think my comment would start a storm. It is simply not true that a 42-11 will "spin out" - that is, be unable to be pedaled faster - at 30 mph. Even for a non-racer 120 rpm is not outlandish for a short time. Saying that one does not want to spin faster than 100rpm is not the same thing.

As for pedaling downhill, it has two functions only - getting maximum exercise out of a ride and keeping the legs warm. If one is trying for maximum speed over a given distance (up and down course) it's wasteful to pedal rather than to tuck and coast, because wind resistance at speed makes the incremental cost of a couple miles per hour too high. It's much wiser to use that energy uphill, where one's effort yields much more at low speed.