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Very recently I've started seeing a setup like this on pretty regular bikes:

Single chainring bike

(Image taken from CyclingID forum)

Appeal of the single chainring

To me the positives of this setup became quite obvious the moment I saw it: fewer parts to clean and maintain, no "dead" chainring-cogset combinations (and the occasional "thumb fight" that comes with it), less clutter on already busy handle bar. Weight is not an issue for me (see below). Price for many new parts is the single disadvantage I can think of, but I'm doing it for fun and money isn't a big problem.

My current bike

I have an older (10-15 years) 26" aluminium frame mountain bike with a suspension fork and hard tail. Shifting is Shimano SLX 3 x 9 with short derraileur tension arm and some very worn out levers. I upgrade and update the bike regularly for both practicality and the fun I get from taking the thing apart and making it a bit nicer. The scale of upgrades goes along the lines of upgrading the supermarket-grade fork to RockShox Tora Air, basic Shimano V brakes to Avid Juicy 5, nice sturdy Remerx wheels and so on. Weight is too horrendous to even mention but I don't mind (and don't want to mind). So basically a very expensive fairly crap bike. The original basic Shimano chainrings are getting old (and too worn, I fear) and I'm thinking about he best replacement.

The question: a small update or big upgrade

The chain, chain rings and cog wheels need replacing, and I'd happily swap the old (and perhaps a bit worn, too) square tapper bearing bracket for something nice as well. I'm not happy with the overal gear change function (caused by old age of the system from levers through wires to improper part combinations I came to over the years) and I'd like to overhaul that as well. So there are two options for me (see further down still), and I want to avoid the possible trap of the appealing and fashionable new thing, the silliness of which I fail to imagine in advance. Are there any downsides of the second option apart from higher part costs? Is there something important I am missing in the shopping list for the second option? Does the second option even make sense?

Option 1 - What I'd upgrade anyway: Chain, cables + cable housing, gear change levers, frame bearing bracket, crank arms with chain rings, cog wheels.

Option 2 - Upgrade to single chain link: Chain, fewer cables and cable housing, one more expensive gear change lever, more expensive crank arms with integrated bearings, new rear derailleur, a new hub with all that goes with it if necessary (I'm afraid it will be).


Update I don't want to buy a new bike even though I'd get more of a modern bike for less money. I'm drawn by the prospect of less shifting and less maintenance and am looking for possible drawbacks or obstacles one can't imagine until one bumps in them mid-upgrade.

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    For extra information, see this older question if you haven't already. Might be some overlap! bicycles.stackexchange.com/questions/40572/… – Smeato May 2 '18 at 9:40
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    You will probably end up spending more money and time to get a worse bike if you upgrade it yourself. Modern bikes are more than just lighter, they have better brakes, better shifting, more gears, etc. I would highly recommend considering a new bike. – Jonathon May 2 '18 at 9:41
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    Guessing your bike is a triple front chainring. Try riding it in the middle chainring only, and see if you run out of gearing at either end. If not, remove the big and little chainring and front shifter. Set the front derailleur as a chainkeeper, and you have a cheap 1x setup. Reverse by refitting all the parts you removed. Done! – Criggie May 2 '18 at 10:03
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    Modern 1x gear setups tend to have a much broader gear ratio than was available on older systems. The very latest can fit 12 gears into the rear cassette. This might be of interest. – T_Bacon May 2 '18 at 11:15
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    FYI 'cable tube' = cable housing – Argenti Apparatus May 2 '18 at 11:39
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The more general form of the questions is: is it worth upgrading a bike vs buying a whole new bike?

In many cases it is not worth it. Individual upgraded components are compromised by remaining lower end ones. Full upgrading of components is as expensive as a new bike. The bike is still saddled with older technology (such as rim brakes).

However, if the point is to mess around wrenching on a bike, give it a new lease of life, the components to be replaced are worn out anyway, and the limitations are well understood; then that in fine. Especially so if the builder is prepared to spend some time on Craigslist and Ebay finding cheap serviceable parts.

[Full disclosure - I own a mountain bike with components spread over two decades.]

  • As I mention in the question, my bike is actually quite in a good shape component-wise. Buying a whole new bike now for a tenfold price of theintended coponent set I'd have the same worn-out components to replace in another five years (even the same-level bike would come at four times the money, and I'm not inclined to spend so much just to change the status of my bike from old to new). – Pavel May 2 '18 at 12:28
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Your question is not about the financial aspect of getting a new bike vs upgrading the current one. It is rather "which upgrade should I go for", as I understand.

To summarise, you have two options:

  • stay with current setup, which is 3x7, I presume
  • go for a modern one 1x11 or 1x12

In both cases you need to replace considerable amount of components as both options include maintenance (replacing worn out parts).

But these are the facts. Now for the numbers. With 3x7 setup you don't have 21 gears as you won't ride with chain crossed and also some of the combinations may double (it would be great if you could post your setup with exact number of cogs). In practice you may have like 10 to 12 effective gear ratios.
With a 1x12 setup you have 12 gear ratios, no question about it.

What you should compare, is what is the highest and the lowest gearing ratio you can obtain with your current setup and how does it compare to 1x12 setup (as 12 chainring cassettes are quite fixed, there is some play with front chainring to obtain more terrain or road gear ratios).

If 1x12 setup gives you the same (or maybe broader) gear ratio range, why not go for it? You then hit two birds with one stone (more recent parts on your bike and maintenance done). Of course assuming that you will be still using this bike extensively and not overhauling it for sale (in the latter case you may not claim the money back you had spent on new parts).

The only hurdle I see in switching to 11 or 12 chainring cassette is the rear hub, as you mentioned. It may require complete new wheel, which can be hard to obtain in 26" and rim brakes option. But if you can relace the wheel yourself (or have it done at reasonable costs), the problem is out of the way.

Considering the bottom bracket update - I assume you have a square-taper BSC threaded setup. I would either stick to it and just look for a new crank (for one chainring) or go full-ahead and replace it with a Hollowtech or Octalink (as far as I know there are adaptor sets for BSC shells available).

  • I have Shimano 3 x 9 (I've updated the question, quite important info:). The why not go for it is my stance all right! My only fear is finding out it won't work mid upgrade (hence the question). A nice hollowtech bottom bracket would definitely look cool, and isn't much too expensive. The rim brake is not a problem, I already have nice disk brakes. You are right with the rear hub, I have a Novatec, but I suspect the bearings are no good anymore, so not much of a shame anyway. – Pavel May 2 '18 at 15:36
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    I understand your fears. Again, the hurdles are rear hub and disk brakes - many people on this forum claim that if your frame is not suitable for disk brakes - it won't work (all those bolt-on brackets for brake calipers are not reliable). Nevertheless, if you can overcome those, the rest is simply replacing/removing the derailleurs, shifters, chainrings and cables. And getting used to new gear ratios. – Mike May 2 '18 at 19:56

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