3x8 to 1x8 (with expansion to 1x10/1x11 in the future)

Question

I plan on converting my MTB fron 3x8 to 1x8.

I plan on leaving the rear derailleur as it is, or I would prefer not to upgrade it to save money.

My current crankset is a 3x8 square taper crank, I have yet to measure the bottom bracket but it'll be probably a 68 or a 73 shell, with standard BSA/ISO threading.

Part list installed:

Crankset:

https://www.paul-lange.de/shop/de/shimano/alivio-acera-altus-7-8-fach/kurbelgarnitur-altus-trekking-fc-m311-vierkant-78-fach.html

Bottom Bracket:

https://www.paul-lange.de/shop/de/shimano/innenlager/innenlager-bb-un26-vierkant-bsa.html

Part list to purchase:

https://www.bike24.de/1.php?content=8;product=164399;menu=1000,2,88;mid[70]=1;pgc[7296][7301]=1;orderby=2

https://www.bike24.de/1.php?content=8;product=7192;menu=1000,2,81;mid[77]=1;mid[282]=1;mid[170]=1;pgc[10624][10627]=1;orderby=2

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My question's/troubles:

BSA threading is universal/standardized right ?

If I purchase a 1x10 crank or a 1x11 crank for example I could install it on 1x8 setup right ?

What compatability issues should I look out for ?

Are the listed parts compatible with each other ?

Answer 1

1. It's unclear if you mean versus other standards, or if there are different kinds of BSC/ISO (BSA is kind of a misnomer, and in my opinion it's clearer just to call it all ISO, because that's the standard that current examples are actually made to). Some road bikes are still made with Italian, but only a couple brands, and bottom brackets can still be had for all the old national sizes. Other than that, yes ISO is the only threaded standard left. Each ISO BB is made for a certain shell width, or widths in the case of the common 68/73/e-type ones that come with 2.5mm spacers you use as needed, but there aren't shell interface differences within ISO beyond that.

2. Yes, no problem.

3. Chain retention tends to be acceptable with just a narrow-wide ring and nothing else helping it, but it's something I'd be looking at when test riding the new setup. Of all the many rear derailers in the world, you could probably come up with some that didn't pull on the chain adequately. It's also good practice to start a new chainring out with at least a new chain and ideally also a new cassette. (This is now less true of the cassette since suddenly it's much more common for people to have extremely expensive ones.) You could skimp on it if they're still pretty fresh, but the idea is that minimizing wear on the ring tends to save more money ultimately. Worn chains can bring a new chainring to their level of wear fairly rapidly.

   • Chainline is also something one should look at when putting a 1x or any other drivetrain together, although it's perennially overlooked and so parts manufacturers do what they can to make it work out okay passively. Buying a dedicated 1x mountain crank with 49mm chainline such as the one you link to and putting it on a normal 135 8/9/10
     rear (which wants a chainline somewhere around there) puts you in the camp of not
     having to worry about it. Other setups create some hoops to jump
     through.

4. Yes, presuming you get the correct version of the BB. (The BSA 68/73 unless it's got an 83 or 100mm shell.) You need an external BB cup tool.