VeloNews’ 1x vs 2x Drivetrain Friction Test - How To Do It Better
Last year the American cycling magazine VeloNews published an article on friction differences between 1x and 2x drivetrains (https://www. velonews.com/gear/gear-issue-friction-differences-between-1x-and-2x-drivetrains/). The article was written by Lennard Zinn who, according to the article, put 1x and 2x drivetrains to the test at Ceramic Speed USA’s laboratory to discover which produces more friction. To my knowledge, this remains the only bicycle drivetrain friction test available on the internet for free. That such a test exists and is available to all is a very good thing. However, the way this interesting test was presented in the article calls for some constructive critique.
First of All...
This is not the 1x vs 2x drivetrain efficiency test alone. It’s the 1x vs 2x drivetrain efficiency test AND the Sram Force vs Shimano Ultegra drivetrain efficiency test at the same time. It’s the two tests in one. This is a fact, not a problem. The problem is that the test was PRESENTED by VeloNews as being 1x vs 2x test alone. Such presentation brings about problems. Some of these were overlooked and some were treated in a rather bizzare way.
I assume we all agree on the following: the bigger the sprocket or chainring and the straighter the chainline, the more efficient the drivetrain will be. Now let’s take a look at the 48/24 chainring/cassette combo which has perfectly straight chainline, and compare it to the 39/19 combo which is 3 cogs off the straight chainline (see figure 1 below. Zinn says: »The 1X chainring was aligned with the fifth from smallest cog /.../ while the 39-tooth chainring of the 2X was aligned with the eighth from smallest cog«). What do we see? We see that the first combo is less efficient than the second one! How is that possible?! How can the combo with perfectly staight chainline and considerably more teeth (as much as 9 more for the chainring and 5 more for the sprocket) be less efficient than the combo with 3 cogs off the straight chainline and with considerably less teeth both on the chainring and the sprocket?
Source and a bigger version of the figure 1: VeloNews.com
Not Seeing the Problem
The article doesn’t pay any attention to this problem. Instead, Zinn discusses various drivetrain parts that create friction. Referring to previous tests he says that the chain creates most friction, whereas different chainring teeth (1x narrow-wide teeth vs 2x uniform-thickness teeth) and derailleur pulleys create no differences in friction. After congratulating 2x drivetrain users, he again briefly mentions some other variables influencing efficiency. About chains he writes: “Past FrictionFacts tests showed Shimano chains to have lower friction than Sram chains; if that difference still exists, one could reduce the difference in efficiency by using the same chain on both drivetrains.”
Wait a Minute...
This is a rather strange claim from the tester himself. It’s like saying: “Congratulations, you won the sprint! This proves you to be a faster sprinter than your brother who’s placed second just behind you. Oh, by the way, dear audience, the brother who won was running in sprint spikes, and the one who lost was wearing heavy mountaineering boots. If this bothers you, dear audience, you could reduce the difference between the two brothers’ results by imagining they were both using the same footwear.”
Chains and Lubes
It should be clear at this point that the efficiency of the aforementioned 48/24 Sram Force combo most likely was deminished due to the Sram (Force?) chain being significantly less efficient in comparison to the Shimano (CN-HG701-11?) chain used in the aforementioned Shimano Ultegra 39/19 combo. The CeramicSpeed’s data (these seem to be the same as those referred to by Zinn) show that Shimano DuraAce chain (CN-HG901-11) saves 0,88–2,26 watts to the tested 11- and 12-speed Sram chains (calculated from the figure 2 below). The average difference in friction between 1x and 2x drivetrain was 2,79 watts. Chain lube is another variable influencing friction. It’s unclear weather the lube used for the chain friction test and the lube used in the 1x vs 2x drivetrain test was the same. Dave Rome remarks in his bicycle chain test that “CeramicSpeed’s chains are using a coating that’s truly special, and the friction numbers between chain models are likely to be far greater with regular lubricants“. Zinn, on the other hand, says that in the 1x vs 2x test both chains were lubed with additive-free mineral oil. Is the „truly special coating” the same thing as the „additive-free mineral oil”? CeramicSpeed would know.
Source and a bigger version of the figure 2: Cyclingtips.com
Toward A Better Test
VeloNews could have at least revealed how much friction each of the two chains produced in the 1x and 2x drivetrains. It’s bizzare that the tester himself only theoretically proposes (to whom – to himself?, to his reader?) to use the same chain on the both drivetrains to find out the actual frictional differences between 1x and 2x drivetrains. The 1x vs 2x drivetrain test should at least have been done with the same chain in order not to measure what wasn’t supposed to be measured, that is, the frictional differences due to different chains! Generally speaking, Shimano chains produce the least friction when paired with Shimano drivetrain, and Sram chains work best with Sram drivetrain. Thus, it would make much more sense to perform the 1x vs 2x drivetrain test with a chain designed to be used with both Shimano and Sram drivetrain and produced by a third manufacturer. But even in this case we wouldn’t know, if this chain generates more friction with Sram drivetrains than it does with Shimano ones, or vice versa.
The Better Test
To exclude noise makers in the 1x vs 2x drivetrain friction test to the highest degree, both drivetrains should be from the same manufacturer and, most importantly, should use the same chain designed by the same manufacturer to work best with these two drivetrains. Also, the smallest cog should have the same number of teeth at both 1x and 2x drivetrain, since the 1x vs 2x drivetrain test showed – unsurprisingly – the smallest cog to be by far most inefficient. At the time being, the drivetrain pair fulfilling these conditions perfectly, is Shimano GRX RX810 1x11 vs Shimano GRX RX810 2x11.
Zinn theoretically admits and practically neglects chains’ significant impact on the drivetrain efficiency. Such an attitude results in the bizzare presentation of the drivetrain efficiency test: 48/24 chainring/sprocket combo with straight chainline is less efficient than 39/19 chainring/sprocket combo with 3 cogs off the straight chainline. The best solution is to perform a new test in which 1x and 2x drivetrains with the same chain and the same smallest cog are compared to each other. One of the drivetrain pairs most suitable for the 1x vs 2x testing is Shimano GRX RX810 1x11 vs Shimano GRX RX810 2x11. Or, Shimano could publish its own 1x vs 2x efficiency testing which probably has already been done. Why should we common immortals live in the dark?
About the author
The author of this article is a cyclist who writes a little, breathes a lot, and is immortal just as you are. He is sponsored by the Mother Nature, highly influenced by the father Sun, and addicted to pure water and fresh air.