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I am looking for suggestions. The chainline is pretty extreme when in the middle front ring and large back cog. I wonder if anyone has seen this and done anything to make the chainline less extreme. That is my favorite climbing gear.
thanks
 

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timn said:
I am looking for suggestions. The chainline is pretty extreme when in the middle front ring and large back cog. I wonder if anyone has seen this and done anything to make the chainline less extreme. That is my favorite climbing gear.
thanks
I've just repalced the outboard BB bearing of my XTR cranks to Race Face X-Type bearings. I've noticed the extreme chainline. In my case the chain tries to jump onto the bottom chainring (this may be due to wear also in the middle chainring). Make sure your cranks are seated correctly in the bearings, a tap with a rubber mallet does this.

Also, for 73mm bottom bracket shell there should be one 2.5mm spacer on the drive side, none on the left side.

Alternatively, although I have not done this, I was thinking of getting the 2.5mm spacer machined down by a bit, not much 0.25mm - 0.5mm. I've got spare spacers so I'll try different amounts. This should move the middle chainring closer to the frame centreline and reduce the angle of the chain in middle chainring, top sprocket. Before I do this, does anyone know of any dodgy effects this might have on overall operation?
 

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timn said:
I am looking for suggestions. The chainline is pretty extreme when in the middle front ring and large back cog. I wonder if anyone has seen this and done anything to make the chainline less extreme. That is my favorite climbing gear.
thanks
Forgot about this. The bottom bracket shell needs to be faced if not already done. But this is a job for the bike shop.
 

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I'm running an XTR 960 crankset and with one 2.5mm spacer on the driveside, there's nothing "extreme" about the chainline when in the middle / granny combo. Like Timn, this is one of my favorite climbing gears and I've never had any chainline issues with this combo.

Now agreed, my situation is with using Shimano cranks, so I'm not 100% sure if the chainline offset would be the same with other brand's cranks, such as Raceface.

Peachy-B, this is not the same issue as with the VPX. The 5.5 has been out for well over a year now and any driveline compatibility issues have been put to rest.
 
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