I am in the process of changing over to 2×10 from 3×9 and have replaced the crank as general consensus on here was that it should run fine with the 9 speed chain and cassette

I’m pretty sure I’ve got the BB and crank installed correctly but the chainline looks quite bad when I’m on the larger cogs of the rear cassette, have I missed something?

swap a BB spacer from right to left?

swap a BB spacer from right to left?

I have considered that but measuring the space between the crank arms and the chain-stays they are identical at the moment so swapping the space would move the cranks off centre

Maybe try a 1mm spacer on the drive side (instead of the 2.5) to nudge it in a bit (assuming you’ll still clear the stays ok?). It’ll still go off-centre, but it’ll pull the chainline in a bit.

(Velosolo have them – very bottom of this page),

@ OP: true but would you notice?

Doesn’t look right does it.

But

What was the line like when it was 3×9? Cause that set up looks as though you’ve just taken the large chainring out. Especially in the last photo.

I think in a 2×9(or 10) you should expect the chainline to look more off due to the fact that the chainrings are moved in towards what would be the middle one on a triple and so at the extremes of the rear cassette the chain has to move out more. My roadie double looks more out of line than an equivalent triple for this reason.

@ OCB, you’d still need to make up the missing 1.5mm?

@Phush1 – Agreed, you’d need a couple of 1mm’s over on the non-drive side too to balance it out overall.

Good point to mention it explicitly tho’ – (I’d just lazily assumed people’d do the maths and stick spacers in the other side to balance it out. 😕 )

My OCD to your OCB 😆

onehundredthidiot – Member

Doesn’t look right does it.

But

What was the line like when it was 3×9? Cause that set up looks as though you’ve just taken the large chainring out. Especially in the last photo.Yeh, so the line to the biggest rear cog from the small chainring should be exactly as it was previously ?

I think in a 2×9(or 10) you should expect the chainline to look more off due to the fact that the chainrings are moved in towards what would be the middle one on a triple and so at the extremes of the rear cassette the chain has to move out more. My roadie double looks more out of line than an equivalent triple for this reason

Only at the small outer cogs, surely.

Ideally the middle of the chainring pair should run through the middle sprocket, assuming you want to use nearly all the available gears.
If not, work out which combinations will be used most and adjust the chainline accordingly. From what I can see, I would move the 2.5mm spacer from right to left and try the bike. I doubt you will notice the cranks being moved across and not being symmetrical with the chainstays (assumes they are symmetrical too, not always the case).

PaulD