Here is one data point for 1X
"1.0" Tactical 1X Drivetrain Setup vs Baseline The "1.0" Tactical is designed to have both a traditional 2X Drivetrain chain ring setup, and a 1X Drivetrain chain ring setup. The small chain ring, front derailleur, and front derailleur mount were all removed for this test.
Drag in Grams @ 30mph Angle Premier "1.0" Tactical 2X Premier "1.0" Tactical 1X Differential -15
429
371
58
-12.5
464
417
47
-10
510
472
38
-7.5
551
527
24
-5
606
595
11
-2.5
647
640
7
0
656
641
15
2.5
654
637
17
5
607
593
14
7.5
523
515
8
10
462
460
2
12.5
402
384
18
15
364
363
1
There is limited data publicly available for the aerodynamic differences a 1X Drivetrain offers over a traditional 2X Drivetrain. To be clear, a 1X Drivetrain setup is referring to a single chainring on the drive side crank arm with no front derailleur on the bike; a 2X Drivetrain is a traditional double chainring on the drive side with a front derailleur. The results are interesting as there’s a small reduction in drag at yaw angles below 7.5, but quite clearly a significant reduction in drag on the non-drive side of the bike at higher yaw angles. It’s speculative, but not overly so, to presume this reduction at higher yaw is due to the missing smaller chainring, as it’s exposure is significant on the non-drive side at higher yaw angles. More tests on different bike models and drivetrain setups would be warranted to come to a more decisive conclusion. Also, it should be noted a rider would likely influence these numbers as the movement of legs, crank, shoes, pedals, etc. would all alter the airflow through the drivetrain area. Still, the results are worthy of further discussion and testing.
Dan Kennison
facebook: @triPremierBike
http://www.PremierBike.com http://www.PositionOneSports.com