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Old 10-11-20, 03:03 PM
  #26  
anotherbrian
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Originally Posted by Tourist in MSN View Post
If he moved the sprockets further to the right, would the parallelogram shape of the rear derailleur put the cage too close to the sprockets? I suspect that the last thing he wanted to do was to make any changes that had the potential to cause any shifting difficulties.

I suspect a better way to improve chainline would be to shift the chainring position with spacers. But, I am not familiar with that crankset and then frame clearance could be an issue too, so maybe that is not practical? From the photo, if any spacers were added, I can't see it.

Photo from article at:
https://cdn-cyclingtips.pressidium.c...3-1080x653.jpg

As chains get narrower with more speeds, is chainline less critical?

I have about a 5 or 6mm chainline error on my Rohloff bike, that has a relatively wide 8 speed chain and that does not appear to cause any increase in friction or reduction in chain life. I wanted my Rohloff bike to have a Q factor that was similar to my derailleur bikes, thus the crankset spindle is about 10mm shorter than it should be. But I would not want to have chainline error greater than that.
I did 50mi+ of 12%+ repeats on a badly (at least by appearance) cross-chained 11spd drivetrain, and while it never broke, looking down at the chainline as I rode was disturbing.

I don't know the actual % loss to efficiencies, but I'd read the larger idler pulleys were very marginal gains, so would think a straight chainline would have to be beneficial.

I think you're right on parallelogram though, at least for road components. A Shimano 1x MTB derailleur (spec'd for 46T but can fit a 50T), can at least clear a 32T sprocket in the 9th gear position (based on Shimano's 11-40, 11-42, and 11-46T cassettes). So if you are satisfied with 32T being your top gear, just put two gears of spacers behind it and set the limit screw (at least for mechanical).

An alternative might be an offset rear derailleur hanger. My Specialized Tarmac disc bike (first gen) had a wonky chainline spacing that required special hubs (135mm SCS) to mimic a traditional road 130mm, however they sold a derailleur hanger that shifted the derailleur outboard to allow regular 135mm hub to be used. It works great, and put the bike back to a traditional 135mm chainline ... add some washers and a longer rear derailleur fixing bolt and it could potentially space it out even further (or have a hanger machined with the extra offset), allowing a regular road derailleur to be used.
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