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I built a 2023 Big Al (boost frame) with a full SLX groupset. It gave me a "perfect" 52mm chain line with the 2.5mm spacer on the DS.
But, has anyone experimented a 51mm or 50mm chainline? I always feel that the 51t would run smoother with a "less bent" chain event at the detriment of the 10t which I don't use much. I have some 1mm and 1.5mm spacers so it would be easy to give the tranny a bias towards the granny.
While I am at it, I didn't sand the BB faces. I can't remember if there was any overspray but probably. Does it need doing? And if so which tool or grade of sand paper do you use?
Cheers
I originally set my Marley up without 1 of the BB spacers by accident. Then I fixed it. Can't say I noticed a difference.
The faces did not need sanding.
Cheers. When you say "one of the spacers", there should only be one 2.5mm spacer used on the DS for a 73mm shell, no?
Off the top of my head I can't remember. I'll check when I got home, however many there are, I initially built it up with one less to no adverse effect. It was only neatness that made me add it after the fact.
I thought the same and swapped the BB spacer over to the NDS to shift the chainring inboard a bit. Gives a better chainline in my opinion.
My opinion is probably wrong in this case but the chain is more or less straight in the middle of the cassette so I can't how how it's better in any other configuration...
On my old Voodoo, I was limited to a 30t oval chainring though as a 32 marked the chainstay. Didn't catch pedalling in the garage but definitely did when riding.
Sounds good Ben. It's always difficult to gauge when the chain is at its straightest but the idea of swapping the single 2.5mm spacer to the NDS sounds good, will give it a go. And if that's going too far then I can tweak with the smaller ones.
Putting the spacer on the wrong side will make the smaller cogs noisier, the chain could scrape against the 11t when on the 10t even if you hardly use it it could be terrible, the cogs on 12sp are so close together so the extreme angles are better off on the descending order cogs rather than the smaller ascending, I run a blackspire snaggletooth chainring on 12sp XT which puts the chainline 1mm inboard making it 51mm, with 12sp I wouldn't wanna go much more inboard than that, chainstays at 435mm, longer stays will fair better though.
Yeh, I preferred my MmmBop setup with the spacer on the NDS. Was running Shimano 12sp.
I also had it setup with shimano 11sp with a non-boost crank/chainring. That also worked really well.
You've just got to make sure your chainring clears the chainstays. Only an issue if using a large chainring (I was using 32t).
Personally I would (and do) space the chainring inboard rather than moving the BB off centre. This is with older 2x and 3x cranks repurposed as 1x setups; 2-4mm depending on crank and whether the frame is boost or not.
https://www.spacycles.co.uk/m8b0s173p3306/SPA-CYCLES-Chainring-Axle-Spacers-large-%28x5%29
(They also do <2mm spacers if you're really anal).
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2x10 XT cranks, 32t chainring spaced in by 2mm gives a good chainline and clears the chainstay yoke on a boost frame (a 34t chainring only cleared the yoke if I ran it without the spacer, but was then sitting just a little too far outboard for my liking).
Cheers Monty. Looks neat but the 12speed Shimano mounts direct on the arm without ring bolts.
I need to take it off to sand the faces potentially anyway so will prob re install with 1.5mm on the NDS and 1mm on the DS to start with to see what happens.