Chain line help - Hollowtech 2

[Roasted]

Chainline looks wrong on my current build, any idea how I can bring it in a bit?

I have a Hope BB with XT Hollowtech 2 cranks and the chainline looks to be at least 5mm too far out. I can't remove the spacers as the axle pokes out the other side unless I stack them all on the non-drive side. It's causing me a bit of a headache.

 

[Southville Hop]

The spacer position will depend on the BB shell size.

 

[Roasted]

I have a 68mm BB so 2 spacer DS and 1 NDS and it looks too far over.

 

[mdvineng]

Move at least one of the spacers from the DS to the NDS until alignment is good. I've seen bb's welded offset before now.

 

[Southville Hop]

Measure from the inside of the middle ring to the centre of the seat tube. Ideally it should be between 48-50mm.

 

[Suprachrgd82]

You can move spacers over from the right side to the left side of the bottom bracket to bring the chainrings in a few mm’s

 

[Roasted]

So I've measured the middle chainring to center of seat tube an it's dead on 50mm.

Next I put on the cassette and tested the chain line with an old chain.

The straightest on the middle is to the 7th gear, I think it should be the 5th.


Small to small looks reasonably straight, just a little kinked



And large to large looks very kinked.



I think I'll try moving 1 spacer to NDS to see what difference that will make.

 

[The History Man]

Might need both.

 

[bikeworkshop]

Triple chainset alignment suffered with the popularity of wide tyres, (2.4s+, early 2000s but still with 135 rear spacing) meaning its common for those running triples on fixed-length bb axles like ht2 to find the chainset's 5mm or so out in the breeze. Misuse of spacers is common - adoption of double and bash an ugly alternative.

 

[nstarmore]

Shimanos current double crankset that is supposed to be suitable for 135mm dropout spacing has a 48.8mm chainline and their 1x cranksets are 52mm!! They've been pushing chainline out for a while now.

I'm guessing this Deore crankset is around the same preiod as the XT one you have and it is listed as having a 50mm chainline:

FC-M590 triple

So it looks like what you have is 'correct' according to Shimano.

If I want a new crankset for a 135 bike now I tend to default to the Stronglight TD2 ones that Spa Cycles sell for this exact reason. I'm not even close to an expert on these things but just prefer it if my chainline is where I think it should be.