1x chainline advice on an old triple crank

So I’m 1x11ing on the cheap by keeping my old faithful triple crankset. I’ve a shiny new NW chainring on the middle position of the spider and am wondering whether I should fiddle with spacers before putting the bottom bracket back on (had to remove it to take off the chain device). It’s a 68mm shell so I’ve a fairly good amount of spacers to fiddle with. Should I leave the spacers alone or is it best to move the line slightly in?

Fit it, look, spin the cranks and decide, we can’t see your chainline.

I would but the cassette isn’t here yet. 🙂 I guess I was wondering if there was a best practise.

Xx1 uses a chainline of 49mm so, use that as a guide I would suggest…

Plenty will be along shortly but probably depends on the rest of the set up. If you have no cassette just hold off the rebuild till you do.

The vast majority of triple chainsets have a centre-ring chainline of ~50mm

M960 XTR = 50mm
M970 XTR = 50mm
M980 XTR = 50mm (for the triple)

Double chainsets of the M980/985 generation are slightly more problematic, but not by much.

I’ve got all the shiny installed now. The chain line looks middleish but when I backpedal in the largest sprocket (the 42t monster) the chain drops down a few sprockets straight away. This doesn’t happen in any other sprocket. Upper limit gear slightly out, or could this be due to the chainline needing to be pulled in a little bit? I’ve two 2.5mm spacers on the drive side so I can easily move one to the non-drive side to pull it in.

will probably still come off anyway, do you backpedal much in 1st gear?

I’d setup the chainline to be best around the part of the block you use most (4-8th?)

You can space the ring on the crank instead of moving the BB spacers around (could be a better option depending on how much crank arm -> frame clearance there is).

@rossburton this seems to be quite common. I’ve got two Shimano XT 1×11 setups one has 48mm chain line (425mm Chain Stay) (32T oval on SLX middle ring inset 1mm by threads on the ring) and a Next SL with 32T absolute black Cinch at 50mm chain line with 436mm Chain Stay.

Neither backpedal in the 42T and both drop to 3rd. In the 37T they both back pedal perfectly though.

I get a quarter back turn on the 42T. I can stop… quarter turn… stop… quarter turn and it’ll usually stay on. Maybe as the chain relaxes a little it’ll do better.

It has annoyed me a couple of times while in boggy ground needing to dab, reset, move, dab, reset. I’ve just ended up having to use the 37T instead of the 42T when I get to that situation.

In every other situation where you’re moving forward and having put 250 miles on 1×11 so far it’s been fine and the shifting is very good indeed.

Dropped the chain once on the bike that hasn’t got a chain guide.

The chain line looks middleish but when I backpedal in the largest sprocket (the 42t monster) the chain drops down a few sprockets straight away.

They do this. It’s annoying but doesn’t affect real world performance much.

Ride it as it is for a bit and see how it goes. If you’re getting no other problems then you have been luckier than many!

chakaping – Member

“They do this. It’s annoying but doesn’t affect real world performance much.”

Unless you’re trying to set off on a steep climb.

Unless you’re trying to set off on a steep climb.

Can you elaborate with details of what actually happened to you?