I know that some have switched to 1x for a mixture of simplicity and aero reasons. Can anyone who has been able to do testing share any aero data? Was the switch to 1x a significant improvement, or just an incremental gain?
Thanks,
-Colin
We just did the testing a few weeks ago. You can see the results that Jim wrote up.
http://www.premierholding.org/pages/quality-control
Edit: to add Jim Manton’s conclusion: 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.
We just did the testing a few weeks ago. You can see the results that Jim wrote up.
http://www.premierholding.org/pages/quality-control
Edit: to add Jim Manton’s conclusion: 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.
Seems to be very conflicting data out there. I have heard rumors that some people claim that bikes were designed with airflow of the chainrings in mind and removing a chainring actually increases drag. I am not so sold on that and I think obviously an opportunity exists to design a bike around 1x but this provides at least another data point. As a DI2 user, I also recognized that the DI2 brake lever is quite a bit bigger than than non-di2 and you get to remove one of those as well.
Those are reasonable numbers. If you can hold good cadence/power over the whole course then it makes sense to switch. You could equally throw those gains away quite easily with a small overgeared effort.
I agree
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As you note, there’s more testing required here to see the effect with and without rider and pedals.
I suspect that some of the gains seen there are from improved airflow through the Ultegra chainring, with fewer high-pressure areas around the bottom bracket.
If one wanted to maximize a set up on the PremierBike Tactical I would do the following: Remove our front DI2 mech and replace with our alloy insert, remove our DI2 shifters on the Bullhorns and use aero brake lever, use 1 X with 50T or less (if possible for your course) and (there was a gentleman that has a company called Arden Design who made chain ring covers) and I would use covers similar to those on both sides of the single front ring. If you notice on PremierBike Tactical - the BB cover extends the down-tube under the bike and (wraps) shrouds the rear wheel. This cover also directs flow and shields the chain from the non-drive side. I would use what ever was required on the rear cog to meet the course requirements. Just my 2 cents.
The 1X test used the same RD as the 2X correct? Any thoughts on what drag change having a mid-cage or long-cage 1X RD would have?
Yes- we did not change anything on the rear for the test. I dont have any data on that for comparison.
One or two watts is what I found.
I doubt the numbers come out the same once you add spinning feet into the mix
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Would it not have been more appropriate to test a 1x Premier against a 2x Premier to understand the advantage of 1x? I know that wasn’t your goal, but it’s not a fair 1x comparison, which is what this thread is about.
The raw data is a blurry jpeg on my computer, so can’t see what margin of error needs to be considered. I love how all these wind tunnel tests are presented as absolutes, rather than X grams +/- y grams.
When we swapped from a double chainring setup to a 54t AeroCoach ARC ring with Hayley Simmonds (UK National TT champion & record holder) there was a ~4w saving at 30mph. Cervelo P5, Rotor 3D SRM, Di2.
We’ve tested a few 1x setups in sessions, on average it’s 1-4w saving from ditching the front mech and losing the inner ring.
I’m thinking about grinding off the derailleur mount and doing a single ring set up to my Speed Concept (frame is pretty beat so I won’t feel bad doing it). Does anyone even make a 55 or 56 tooth drop stop ring???
The Speedconcept is tricky to go 1x without grinding bits off! We make 54t and 58t but have other sizes and a tri specific shape coming. If you don’t manage to find a 55/56 then do some calcs with your rear cassette as you may not need to buy another ring if you’ve already got one, you can just change the cassette instead.
I have an 11-26 11 speed out back and can handle all the hills on our local tt series. I never use the small chainring and would like to eat rid of it, but I really like having a 56 on downhill and tailwind sections.
I wonder how something like this :
Or one of the carbon covers would influence the results (with regards yaw and the inner chainring) ?
WD 
Yes we tested the PremierBike 1 X against the PremierBike 2 X. If you would like a better copy of the raw data please send me a PM with your email. I can send you a copy.
I have been riding 1x for a while now and I can say that in the near future I will be grinding the hanger off shortly. I will drill out the rivets and see how it goes from there.
Those are nice. Zipp and Blackworks also made a beautiful example some years ago. I think Absolute Black is also making something similar. Both sides would be nice.