Old 02-02-18, 03:29 PM
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twocicle
Clipless in Coeur d'Alene
 
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Bikes: Tandems: Calfee Dragonfly S&S, Ventana ECDM mtb; Singles: Specialized Tarmac SL4 S-Works, Specialized Stumpjumper Pro, etal.

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Originally Posted by willhs View Post
I did work it out which parts to buy but didn't do the drivetrain rebuild because the stock drivetrain was good enough (it was for a friend) and they might not be using it enough to justify adding bling.

...

You will need a total of two 34t 110BCD chainrings and one 50t 110 BCD narrow-wide 1x chainring (also called a CX1 chainring). So if you don't get them packaged with the above cranks, you need to buy them separately. You'll definitely need to buy at least one 34t ring in addition.
If you had tried the above, a big problem would have been with that choice of 50t "big" ring. Narrow-wide 1x chainrings are not intended to allow a chain to derail (ie: shift) and so do not have ramps, pins, ramping or tooth profiling to assist with chainring shifting. With the 1x chainring, this setup would simply not shift reliably to/from the big ring.

Solution is simple, just get a matched set of regular 50/34 compact crank 110bcd chainrings, then slap the 34t timing ring on the outside.

You would obviously need to add significant spacers to provide a gap to the timing ring, sufficient enough to prevent chain to chain contact when shifting up to the big ring (chains frequently ride on top of the big ring and a bit to the outside and so can tangle with a SSD timing chain).
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