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My SRAM rear derailleur (Rival 22 circa 2016) has a non parallel movement. When it is in the lowest gear, the cage and pulley sprockets align with the cassette sprockets, but when it's in the highest gear, it is very miss aligned.

Aligned in lowest gear Not aligned in highest gear

I measured the distance between the pivot points. I got 48mm and 49mm, which would explain the non parallel movement.

enter image description here

Question 1: What was the design reason for this?

Question 2: Do I need to get the alignment of the derailleur hanger checked? The gears shift easily. I'm just worried about drive chain efficiency.

  • Have you ever crashed it? Or has the rear mech taken a knock ? – Criggie May 18 '18 at 9:23
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    No. I assembled the bike from new. It was like that from the beginning. – Gary van der Merwe May 18 '18 at 9:40
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    This is only speculation: could the design try to point the derailleur towards the front chainring? Checking the alignment of the derailleur hanger is something I would definitely do. – Christian Lindig May 18 '18 at 12:15
  • Parent avoidance – Rider_X May 18 '18 at 23:53
  • Just a guess, so no full answer: The derailleur has to bend the chain, there is no way around it, because the chain-wheel is fixed. If the chain is bent as it runs off the chain-wheel, that's just a bit of wear. If the chain is bent as it runs onto the derailleur, that's a danger of the chain jumping off the derailleur sprockets. You don't want this. So, the non-parallel movement minimizes that second bend of the chain. TL;DR: This seems to be a safety feature. – cmaster May 19 '18 at 12:20

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