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To obtain a proper chainline for a boost rear hub (~52 mm), is it enough to fit a boost (3 mm offset) chainring to a 1x crankset which is originally non-boost, or is an entire boost crankset required (i.e. not only the chainring but also the crankarms)? Namely, I am buliding a boost bike and can get a very good deal for a SRAM groupset that has a non-boost DUB direct mount crankset. The simplest and cheapest way to go for me would be to buy the groupset and replace only the non-boost chainring (6 mm offset) with a boost variant (3 mm offset), while keeping the rest of the crankset. Would this work?

  • I've done a little research in the meantime, and, at least for SRAM cranksets, it looks like changing the chainring is enough. That is according to page 14 of their Chainrings and Spider User Manual. In particular for all DUB and 24 mm spindle cranksets, it seems that one should use 6 mm offset chainring to get non-boost, 49 mm chainline, and 3 mm offset chainring for boost, 52 mm chainline. However, I'd like to confirm this with someone who has actually dealt with this issue. – Mick Jul 18 '18 at 8:53
  • I'm pretty sure you've got it right, at least in terms of the current SRAM direct mount cranks (i.e. that the cranks themselves are same, and the only thing that makes a crank the boost version is it comes with a 3mm offset ring as opposed to 6mm). – Nathan Knutson Jul 18 '18 at 19:42
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Answer: The entire boost system has to be used with all the pieces together to have a proper chainline 53 mm to my taste.

I've already had a boost hub, and a non boost entire crankset. At the end of the first month the chain touched the frame. On a race I confirmed a noisy chain, and finally had some missed shifts (twice).

Exactly what I have been searching for 3 weeks now, and found that as SRAM and one up moves the just chainring, and Shimano offer change the crankarms.

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  • Could you please elaborate on what exactly you mean with "i found that as SRAM and one up moves the just chainring, and Shimano offer change the crankarms." ? Thank you! – Maarten -Monica for president Dec 16 '19 at 0:05
  • Concur - I'm not sure what point you're making in the (now) last line. Can you please edit that to explain further? BTW, welcome to SE and thank you for your first post... do take a moment to read the tour to learn how the site works. – Criggie Dec 16 '19 at 23:17

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