how to fit 36t or larger chainring on 2015 niner air 9 RDO?

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how to fit 36t or larger chainring on 2015 niner air 9 RDO?
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flag jensnorman
Posted: Jan 29, 2020 at 12:05 Quote
I was naively thinking I could easily convert my 2015 Niner Air9 RDO into a gravel bike by swapping the 32t front chainring for a 40t.

Then I realized that Niner doesn't recommend anything larger than 32t in front.

Is there a way around this, by using an offset chainring to get to a 36t or 38t?

Here is what I have to work with:

non-boost spacing - 49 mm chainline
sram XX1 cranks with bb30
it looks like a direct mount chainring
68 Q-factor
appparently short spindle

wolf suggested an offset chainring, but i am not sure how much space that would buy me. also I am not sure how this would affect shifting.

any insight would be much appreciated!
flag joshsaxe
Posted: Feb 12, 2020 at 11:21 Quote
jensnorman wrote:
I was naively thinking I could easily convert my 2015 Niner Air9 RDO into a gravel bike by swapping the 32t front chainring for a 40t.

Then I realized that Niner doesn't recommend anything larger than 32t in front.

Is there a way around this, by using an offset chainring to get to a 36t or 38t?

Here is what I have to work with:

non-boost spacing - 49 mm chainline
sram XX1 cranks with bb30
it looks like a direct mount chainring
68 Q-factor
appparently short spindle

wolf suggested an offset chainring, but i am not sure how much space that would buy me. also I am not sure how this would affect shifting.

any insight would be much appreciated!

You may be able to cheat the clearance by using an Ecentric BB which would move the bottom bracket forward and away from the stays. I've done this with 38T chainrings, but not on a 2015.
flag Allpedalsnobrakes
Posted: Aug 7, 2023 at 8:43 Quote
jensnorman wrote:
I was naively thinking I could easily convert my 2015 Niner Air9 RDO into a gravel bike by swapping the 32t front chainring for a 40t.

Then I realized that Niner doesn't recommend anything larger than 32t in front.

Is there a way around this, by using an offset chainring to get to a 36t or 38t?

Here is what I have to work with:

non-boost spacing - 49 mm chainline
sram XX1 cranks with bb30
it looks like a direct mount chainring
68 Q-factor
appparently short spindle

wolf suggested an offset chainring, but i am not sure how much space that would buy me. also I am not sure how this would affect shifting.

any insight would be much appreciated!

What did you end up doing? I have a race in November that is about half suited for a gravel bike and the other half is more suited for a MTB. The course is layout is below:
- 4-5 miles of hilly pavement leading up to the first climb.
- First climb is about 600' over 3 miles and a descent down to the starting elevation.
- You then have about 2 miles of "flat"
- Then a massive 2700' climb over 10 miles which also descends back to starting elevation.
- Following that, you have 15-18 miles of rolling gravel/pavement. This is where my race set up on the gravel bike was able to shine. I ran a 34/50 chainring and 11-36T cassette. We were able to average 20 mph over this terrain. With a 32T chainring on the MTB, even in the 11T on the cassette, I'll likely spin out on this section.

Both descents are very rough and washed out fire/service roads in Appalacia. The time I scouted the route on a gravel bike, it's just not made for that level of roughness on the descents. I think I can make up serious time on the descents with the MTB but if I can push a larger chainring, it'll make the "flats" that much faster. If you couldn't figure anything out, not a big deal. The race organizers have said in emails, "bring whatever bike you desire, it'll still be the wrong bike for the race," so I know whatever I choose isn't going to be perfect.
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