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About ten years ago, I built myself a new bike, for general utility riding and some light trips through the countryside (tens of miles on towpaths etc). I was most familiar with the classic (hardtail) mountain bike technical ecosystem, so that's what I used. Over time, various parts have worn out and I have replaced them. Most of the drivetrain has now worn out again, and I am looking to replace it.

But everything has changed! Some of the parts I want don't exist any more, and some do, but seem like they are on the brink of extinction. So I wonder if I should take this opportunity to bring things up to date. Can I do this, or are there features of my bike which make this impossible?

The bike currently has:

  • 26" wheels
  • quick releases
  • a square taper bottom bracket
  • a triple chainset (24, 38, 48 - this works, if only just)
  • a 9-speed cassette (11-34)

Specifically, what I need to replace is:

  • Chainrings
  • Chain
  • Cassette
  • Rear mech
  • Rear hub (the freehub body is malled; there are no replacements, so I need a whole new hub)

What I would quite like to do is move to a 2x11 setup, while maintaining a comparably wide range of gears. Is this possible? What do I need to check to make sure it will work?

Does anyone make cranks for square taper bottom brackets any more? Does anyone make hubs for quick releases? Can I switch to thru axles? Will I need an XD hub? Do I need to worry about this boost geometry stuff? Are there chainline considerations? Can I use my current front shifter and mech with a double chainset? Do 26" wheels make me an irredeemable caveman?

I realise this is a bit of a vague question. Part of my problem is that I don't know what I don't know!

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    Rim brakes or disc brakes? Do you want to keep them? Commented Sep 24, 2022 at 17:44
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    Consider that cycling itself hasn't really changed - you push pedals, bike goes forward. Try searching for a better bike shop in your area, it should be crowded and not sell running shoes/clothes.
    – Criggie
    Commented Sep 25, 2022 at 4:31
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    In addition to the answers you've gotten, I would ask you to also consider whether the bike/frame has any sentimental value to you. In that case, the monetary cost could well be worth it, especially if you are doing the work yourself. There is a ton to be learned from choosing, ordering, and (de-)mounting components on one's own -- the experience gained is invaluable, but the parts alone will be costly (let alone the time+tools needed). IMO if you intend to pay somebody to do the work for you, then the better solution is to sell this bike and buy a "better" one, as mattnz's answer suggests.
    – jayded-bee
    Commented Sep 25, 2022 at 12:58
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    Would have upvoted "irredeemable caveman" alone :-). And my bike is 20 years old, what does that make me? A troglodyte? Commented Sep 26, 2022 at 6:04
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    @TomAnderson you state 'everything has changed" when that's not really the case. If your parts source only carries 1-by parts, don't get railroaded into expensive run-on upgrades - find another bike shop that carries the parts you need. Don't assume that newer is better than older. Stuff's got expensive lately.
    – Criggie
    Commented Sep 27, 2022 at 23:08

3 Answers 3

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Despite the massive moves and designed obsolesce, with marketing and social media driving all the hype over the latest and greatest next best thing, the parts to maintain the bike are readily available. Walk into any half decent bike shop and they will have the most commonly worn parts on the shelf (e.g. square taper BB) and be able to order anything you need.

I have a similar aged bike and replace worn bits as needed. The modern upgrades that count are wheel size, geometry, though axles and boost - things you cannot change. The rest are really incremental increases in performance. 1x over 2x vs 3x is about frame design and removing the front derailleur from the crowded BB area of squishies but requires 11 or 12speed to get decent range without too much jump between gears.

Be very careful not to spend more than the bike is worth, especially if you are paying someone to do the work and not doing it yourself. I would replace what is broken and not look to changing much - only thing I might consider is 3x to 2x with a bigger (e.g. 11-42) cluster, at the same time (due need for new cranks) going to more modern BB/Cranks, but only if I could get all that at a the right price.

Consider selling the bike and putting those funds and cost of parts towards an new (or used) bike.

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    It's always a conundrum: Repairs/upgrades may cost more than the market value of the bike (before repairs ;-) ), which is often quite low. But buying a new quality bike is still much more expensive. Commented Sep 26, 2022 at 6:17
  • Damn right about the hype! The thing is, what is a "common" part has changed. I currently have a SRAM X7 rear mech. I cannot buy one any more - i can't find anyone selling one. Is there any good quality SRAM-compatible 9-speed rear mech still widely available? How much longer will there even be decent 9-speed cassettes? Interested to hear you might consider changing up the chainrings and cassette though. Are you talking about an 11-42 9-speed, or an 11-speed etc? Commented Sep 27, 2022 at 20:13
  • As for selling the bike - the resale value rounds to zero. It's a self-built Frankenstein's monster of old and weird parts (handlebar and stem reused from a Decathlon bike, Ergon grips worn to the shape of my hands, no-name carbon fork from Superstar, rack held on by a P-clip because there's no holes on the seat stays, etc). Meanwhile, an off-the-shelf replacement of similar quality would cost ~£1000 i reckon. So repairing definitely makes sense. Commented Sep 27, 2022 at 20:17
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A large 11-speed cassette with 26" rear wheel is tricky. The derailleur arm is very long in comparison to the wheel and the ground clearance is quite poor. But a good news is that usual hubs are compatible (if you are fine with 11t being the smallest sprocket, otherwise see Renaud's answer for XD hubs), you do not need a dedicated 11-speed hub like on road bikes. It is doable, but risks exist.

Square taper cranks: Yes, there are many square taper cranksets available. However, do not select your crankset based on your bottom bracket. Select your bottom bracket based on your crankset (the BB is much cheaper and must be replaced from time to time).

Thru axles: No, if you want to keep your frame, you must use what frame supports. That is likely a QR skewer.

Boost: Yes, you need to worry, your new wheels/hubs must be non-boost. No, your old frame cannot be expanded to boost.

Chainline: Just get the compatible set of components for your crankset, front derailleur, rear derailleur, cassette, bottom bracket and you will be fine.

Front shifter: If it is a friction on, you could reuse it, but just get a proper indexed 2x one.

Caveman with 26": Depends on individual taste. But for serious racing they are obsolete. And they are problematic for very large cassettes and their derailleurs.

Also:

Brakes: If you have rim brakes, you can check whether your frame also supports disc brakes. If you want different disc brakes, be careful about the mount standard used. It could be the old IS mount.

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    Regarding bottom bracket: different square taper cranks require different axle lengths so you’ll probably need to replace it even if you keep square taper.
    – ojs
    Commented Sep 25, 2022 at 9:15
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    IMO the Hollowtech II external bearing BBs are a substantial improvement over square taper BBs, and at this point no more expensive. Of course, you will need a crankset compatible with Hollowtech II.
    – Armand
    Commented Sep 25, 2022 at 10:29
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    Re: rear hub. Consider just having a new 26" rear wheel custom-built for you with a rim that fits your style and a good-quality rebuildable hub. For example, I get 26" wheels made with 32 spoke rhynolite rims and XT M756 6-bolt hubs (both available at reasonable prices as new old stock etc on ebay and similar locations. That way I can use rim brakes or disc brakes as I choose, and the wheels have tank-like robustness.
    – Armand
    Commented Sep 25, 2022 at 10:34
  • @Armand The reason i chose square taper in the first place is that, with a good cartridge, it needs little to no maintenance. I've been riding the same one since i built it, with no maintenance and no issues. I could switch to an external, but now i have another thing i need to lubricate regularly. Commented Sep 27, 2022 at 20:21
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    @TomAnderson AFAIK Hollowtech II BBs require no more maintenance than do square taper BBs. Nothing to lubricate -- the bearing cups are disposable, just like square taper cartridges. By "rebuildable hub" I just mean one that you can service and replace bearings (whether balls or cartridges) when they wear out. Many lower-end hubs (and thus wheels) have to be tossed once the bearings wear out.
    – Armand
    Commented Sep 27, 2022 at 21:29
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TLDR: "modernizing the bike" will bring loads of complications for questionable benefits, and serious drawbacks in all cases.

About the availability of the standards:

  • QR: still the norm on entry level MTBs, and some trekking bikes.
  • Through Axle, Boost: these require frames built for these standards. Some may argue that you can upgrade the fork, and take one with a TA (if such exist)
  • Boost (bis): Shimano has different references of hubs, cranksets and front derailleurs. Be sure to take the non-boost version.
  • Square taper: still available on entry-level ranges, but you can remove the bottom bracket by a another kind. Some cranksets also allow to replace the chainrings separately, so that may not be relevant.
  • XD hub: only required if aiming for a smallest sprocket of 10 teeth (or 9). Note that Shimano has release a competing format, called Microspline. Shimano has one QR hub with this format (FH-MT401).
  • transmissions like you have are sold as "trekking" nowadays, they still exist and sell well. However, if you have Deore or better, you may be better off keeping your mechs and just replacing the worn elements, as the current trekking Deore and up are 10-speed.

About upgrading to a 2x11, two notes:

  • recent MTB groupsets are designed for 29" wheels (that require lower rotational speed of the wheels for the same speed). Largest chainrings are 36T on the lastest Shimano 2x.
  • unless you upgrade to latest SLX or XT, expect less range than what you have now. Your current set up has 620%, a Deore M5100 530%. To improve the range, you would need to go the SLX/XT range (2x12, Microspline, 630%). But that will probably cost more than the value of the bike, and will also have a lower top speed than what you have now. But the cost will probably excessive compared to the value of the bike.

In term of ratios/ranges, having a modern 2x11/2x12 on 26er would be equivalent to removing your largest chainring, and fit another one, smaller than your current smallest. Whether it's a benefit or not depends on your use case.

If you are happy with your current range and ratios, and want a modern system 2x, the best option would be a 2x9, with an Acera 46/30 in the front, and a Microshift Advent (long cage) in the rear (with a 11/42 cassette). The benefit will be less chainring changes when riding, the inconvenient will be the cost, less intermediate steps (I anticipate some comments, with a 9-speed 11/42, you may not have enough intermediate steps) and more importantly less availability of parts (because these components are a "low end niche", while trekking remain more widespread than what the "coverage" of these products let think).

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  • Ah, i hadn't considered the point about ratios being designed for 29" wheels. Really interesting to hear about "trekking"! Which manufacturers make trekking parts? I have bought a lot of SRAM in the past, but it seems they don't? Commented Sep 27, 2022 at 20:28
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    @TomAnderson I don't think SRAM does. But Shimano has a trekking range, that may be a bit confusing because they use the same names as MTB ranges, but reference numbers start with T instead of M. What you have is very close to the Alivio range (T4000 series). bike.shimano.com/en-US/product/component/alivio-t4000.html
    – Rеnаud
    Commented Sep 27, 2022 at 21:51
  • Superb, thanks! Commented Sep 29, 2022 at 18:51

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