1x chainline

What does the chainline measurement on the specs of cranks mean, exactly?  I saw one that said 49mm – how does this compare to the middle ring of a triple?

Chainline in the big sprocket of my 1×9 isn’t great – will a 1x crank be further in?  Don’t fancy the chanline if I have two more sprockets even further in.

Should find all your answers here…

https://www.oneupcomponents.com/pages/understanding-chainline-for-optimal-1x-conversions-boost-and-non-boost

And yes, dedicated 1x and/or boost or even 2x cranks have the rings in different places relative to a triple…

Middle ring of a triple is 47.5mm according to Sheldon, although may be a little wider, so dedicated 1x cranks may well make it worse.  IMO, “standard” 1x chainline is too wide, giving quite extreme chain angles on the big sprockets.  My SRAM 1x CX bike which has cranks on road chainline worked better than my XT M8000 1x setup, at least until I spaced the M8000 in by 4mm from stock.

Wolftooth seem to agree:

So a perfect 1x with minimal cross-chaining in the big cassette cogs is 46-47mm.  You might ask why SRAM designed a dedicated 1x drivetrain around a 49-50mm chainline, and the answer is very simple:  most bikes would only clear about a 28t chainring at a chainline that narrow and the most popular 1x sized chainring is a 32t with many riders wanting 34t and 36t options.

Can you move an BB spacers from the driveside to non-drive side?

I’ve moved the BB spacers across – you might also want to consider going for an sram cassette rather than shimano as the shimano hasthe big ring more towards the spokes.

Can you move an BB spacers from the driveside to non-drive side?

Yes but the cranks wouldn’t be in the middle then.  Not sure I could deal with that.

I wonder if boost hubs improves chainline?  Of course I’m tied in to normal with this bike but just made me wonder.

I posted a thread about chain and cassette wear a while ago with 1×11 and most people seemed to think that their chains didn’t wear unduly and the cassettes lasted much longer than with 3×9 – so the out-of-the-box setup would seem to be ok even if the chainline looks bad…

I’m sure clutch mechs will push the wear rate up – the noise and resistence when the clutch is engaged is much more.

Note sure you will notice moving the BB spacers – I suppose it depends how much float/movement your pedals allow.

the sram 12 speed chain is suppossed to be better at coping with the chainline angles.

Another reason for having a chainline outboard of the middle of the cassette is that in top gear the chain can foul (top-1) gear.  I did notice this when using non-boost cranks and chainline with a boost rear end, but it wasn’t a deal-breaker for me (though I now have a direct mount system and have gone for a boost chainline).  That was with a 2-tooth jump between those gears.

Sometimes you’re limited by the frame, when I changed to 1×11 on my hardtail I was using a 34t front ring and even with it virtually touching the frame the chainline in the lower gears was awful. It caused a lot of premature wear on the chain and chainring.

I’ve changed to a 32t front ring now just so I could move it further inboard and improve the chainline a bit.

That’s using the middle ring of an xt triple crank with spacers.

I wonder if boost hubs improves chainline?  Of course I’m tied in to normal with this bike but just made me wonder.

Boost hub with boost crankset maintains the same relative chainline (both move out by 3mm).  Boost hub with non boost crank potentially gets you a better chainline if you have the clearance for it.

Another reason for having a chainline outboard of the middle of the cassette is that in top gear the chain can foul (top-1) gear.

I’ve read that this is a bigger issue with 12 speed, although I can see that a 2 tooth gap between these sprockets would also make it worse.

Pretty sure having the chainline offset to the left/low gears is going to be mechanically best, since those are the gears you spend the most time pedalling in generally. But personally, I’m convinced it doesn’t really matter, in the amounts we’re talking about here, the cassettes and chains don’t seem to mind at all.

For 1x systems you should be choosing a chainring where most of your riding is in the middle of the block which for an 11spd cassette I’d define as gears 3 – 9. Then you spend a bit of time in 2 & 10 and very occasionally in 1 & 11. I.e. if time is the y axis and the gears are along the x-axis then usage should be similar to this:

Those who have them electric gears – do they keep data on gear usage you can subsequently download?  And if anyone has – does it follow a normal distribution?

Not sure that applies in this case whitestone.  As MTBers we spent most of our actual pedalling time going up steep hills.  We don’t pedal much on the descents, and on flats if there are any we are generally pedalling more lightly.  Unless you ride at Swinley a lot.  Certainly for me on local rides (which is where this bike goes) most of my time is pedalling in low gears, and this is when I pedal the hardest so I’d estimate the middle of the distribution is close to the biggest sprocket.

Was under the impression triples were offset, so the chainline was straightest when on the smaller most used sprockets, to minimise wear.

Measured the chain line. About 54mm ish, even after my extreme spacer mods. Cannot go in any further cos it fouls my chain guide bracket.

Well, wheel.lookong down at the bike I realise that the chainstays are obviously highly asymmetric. So suddenly makes sense now. I moved the chainring spacer from the drive side to the none drive side and, well, it helped a bit. But the chain guide no longer fits so I’ll have to modify it since the chain dropped a few times. Funnily enough, not whilst on rough off road, but when shifting across the block