chainline on 2 x 10

alexm77

I'm doing a complete overhaul of my drivetrain on my Inbred 456. Everything with the exception of the front mech is being changed from 3 x 9 to 2 x 10 (all SLX).

I've managed to get it set up okish, but when I go big to big, I can see the chain line isn't great, and it feels like cogs and chain are grinding a bit laterally. I suspect I might have set the bottom bracket spacing up wrong. It's a 68mm bb, with 1 x 2.5mm spacer on the non drive side and 2 x 2.5mm spacers on the drive side as per instructions here http://cycle.shimano-eu.com/media/techdocs/content/cycle/EV/bikecomponents/FC/EV-FC-M675-3397_v1_m56577569830801180.pdf

I can't seem to find any info on what spacers to use with different bb shell sizes, but is this the correct setup, and I just shouldn't go big/big on a 2 x 10?

Thanks,
Alex

benpinnick

No its right, 2x10 doesn't give you 20 properly usable gears, more like 16 or 17. That said under load you'll notice it a lot less.

The Rookie

Not all hubs put the rear cassette in the same place, between my Superstar and a Shimano rear hub they are pretty much spot on one gear out, that means the nominal chainline may not match your cassette and exacerbate the cross chaining in one direction and leave it not so bad in the other.

alexm77

Ah, I've got Superstar Evo hubs, so don't know if that's an issue then. Can't say I noticed any changes to the chainline when I originally changed from deore to superstar hubs when I was on 3 x 9.

It feels like I should just swap the second spacer to the non-drive side, which would move the chainset in 2.5mm. Would mean the small/small chainline would be worse (it's not as bad as big/big), but I'm pretty unlikely to go there very often, whereas would be nice to get the whole range on the bigger front cog, as I imagine I'll be using that one 90% of the time.

Antm81

If you're using the big ring 90% of the time why 2x10 instead of 1x10?

alexm77

for when I'm too knackered to make it up that big hill otherwise Isn't that the reason anyone has a granny ring, it's a bit like insurance, nice to know it's there just in case!