Q:

Sub-compact chainring sizes?

I am looking for replacement chainrings for a mechanical, 2x Sram 11 speed drivetrain and was wondering if I can find chainrings anywhere that will fit the road bolt pattern of a standard crank but are smaller than 50/34 tooth size?
It's pretty easy to find 1x chainrings in smaller sizes for road and mountain, but Sram does not sell anything smaller than 50/34 for 2x sizes.
Does anybody make sub-compact chainrings in a size smaller than 50/34?

A:

We shy away from specific product recommendations, but the question is a decent one and it's impossible to answer without mentioning specific products. So, here goes.
I assume that "standard crank" means 5-arm cranks with a 110mm bolt circle diameter (BCDs). Many manufacturers are moving towards 4-arm cranks with 110mm BCDs, but their chainrings may not be mutually compatible. (FYI, I believe Shimano started this trend with Dura Ace 9000.)
Not Many Options for "Standard" Compact Cranks
110mm chainrings are limited in their minimum size. For 110mm BCDs, 33 teeth is generally the smallest you can get. This is due to the physical limits of how small a circle can fit to that diameter. TA and Stronglight, both French companies, make various chainrings down to 33t. The links go to one retailer in the US who sells them. If you are in the US, I am not sure if Quality Bicycle Products, which is a major distributor for cycling goods, can get these specific rings. Wickwerks makes a 41/33t cyclocross chainring set for 110mm 5-arm cranksets, but this combination may not be good for general purposes. In any case, it illustrates the fact that you generally cannot get chainrings smaller than 33 teeth on a standard 110mm crankset. I believe this only produces a 3.0% change in gain ratio.
Some readers may think of the Praxis Zayante 110mm 5-arm crankset, which comes with 48/32 chainrings, and wonder if my statement above is correct. It is. Praxis' note on their chainrings says that the 48-32 set is only compatible with their own crankarms. I don't recall the specific reason, but they may have done some custom machining to the rings or the crank spider to enable it to fit a 32t chainring. I read this in one of their site's technical documents.
Absolute Black do appear to make chainrings with effective gearing of 48/32 for any standard 5-arm 110mm BCD crankset. The catch is that they are oval. Not all users may like them, and it is more difficult to set up your front derailleur. There are some claimed performance advantages for oval chainrings, and I believe Chris Froome used or still uses them. However, these claims aren't clearly backed by research.
If you just meant to change the outer ring, then your problem is much easier. Standard cyclocross double gearing is 46/36 teeth, with some riders opting for an outer ring smaller than 46. These should be easier to find. However, I suspect you are looking for easier gears. This would entail searching for road sub-compact cranksets, as detailed below.
Sub-Compact Cranksets
If you are willing to change the crankset and bottom bracket, your options expand. The Praxis Zayante crankset described above is one option. There are a few more outlined here, some of which have 46/30 chainrings. However, again, many of these options will require a new bottom bracket. I am not aware of any specific options compatible with SRAM GXP bottom brackets.
As you already ride SRAM, I'm compelled to mention that the SRAM DUB 12-speed cranksets have a 46/33t chainring option, but they are very expensive and I believe they require SRAM's own DUB chain.
You'll Need Other Options
Everything on a bicycle is a compromise. If you need lower gears, a wider range cassette is an option. However, it may require you to change your rear derailleur. Not all riders may like the gaps between cogs in group rides: you need to match the group's pace at a cadence you find acceptable, and you may find yourself wanting something between cogs. This may be less of an issue on solo rides. I believe SRAM shifters don't support triple cranksets, and you will need to revert to 10s Shimano or Campagnolo groupsets. Campagnolo's older Athena 11s groupset, released around 2010, had a triple version, and new old stock parts may be available from some retailers.

