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When I bought my Quarq DFour for Dura-Ace 9000/Ultegra 6800/105 5800 chainrings last year, I had planned to mount my o.symetric 50/34 chainrings. However the asymmetric shape of the inner ring couldn't be mounted due to a ring of some sort on the crankset.

Luckily, I had a pair of absoluteBLACK 50/34 oval chainrings collecting dust which could be mounted and works like a charm (although I still prefer the shape of the o.symetrics).

I'm planning a mountainous 4,000 km ultra endurance race, and hence want the following gearing: sub-compact 48/32 chainrings and a 11-34 cassette (or 12-34 frankensette).

Since I couldn't mount the inner o.symmetric ring, I'm afraid that the inner absoluteBLACK 32t ring won't fit. Will it?

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  • Try it and see?
    – Adam Rice
    Sep 20, 2020 at 13:41
  • I'm not clear why the Osymmetric chainrings wouldn't go on the Quarq DFour spider. In theory, I would expect them to. I would expect that the Absolute Black 48/32 rings should have the exact same BCD and shape at the mounting points as their Shimano counterparts, it's just that they would have an effective gearing that's lower. All this is in theory, however. Unless someone has practical experience, you might just have to order a pair and return them if they don't fit. Good luck with the race!
    – Weiwen Ng
    Sep 20, 2020 at 13:41
  • "Try and see" - too expensive and cumbersome.
    – T0TTE
    Sep 20, 2020 at 16:07
  • The o.symetric 34t chainring won't mount since the aforementioned "ring" of the DFour is too big. Try and see ;-)
    – T0TTE
    Sep 20, 2020 at 16:09
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    I don't know the answer, but what I'd be looking at is how close is the 34t ab ring to not working. I assume but don't know that the 32t is similar but scaled down.
    – Nathan Knutson
    Sep 20, 2020 at 16:34

2 Answers 2

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A way of getting a pretty good guess is find a laid-flat image of the ring in question, open in photoshop or gimp or cad or whatever, make some paths or circles that exactly cover two opposing bolt holes, then make a line between the centers. Get the measure of that line in whatever application you're using and the irl physical measurement of your spider, and then make a circle whose center is the midpoint of the line and whose diameter is scaled to the in-image length of the line as ratio between the spider diameter in mm and 110. That should give you a good idea whether it's way off, may take minor filing, etc.

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No, absoluteBLACK's sub-compact inner rings (i.e. 32t and 30t) cannot be mounted on a Quarq DFour for 11 speed Shimano chainrings.

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