Editor’s Note: Lennard Zinn’s regular column is devoted to addressing readers’ technical questions about bikes, their care and how we as riders can use them as comfortably and efficiently as possible. Readers can send brief technical questions directly to Zinn.
We’ve received a lot of mail related to VeloLab’s chain lube test in the March 2013 edition of Velo magazine. After answering rueful reader questions lamenting the results, which showed that paraffin wax was the most efficient lube (we didn’t test for durability, merely power savings), this week I’ll address one reader who asked about the importance of regular maintenance versus lube choice.
The numbers on lube efficiency over distance
I agree with you that regularly cleaning the drivetrain and lubing probably makes more difference than what lube you use. I spend 10 minutes wiping my road bike down after each ride, including drivetrain components, and lube the chain about every 80-130 miles. I measure my chain with a chain checker and get 4000-5000 miles out of each one. I can see how lube efficiency might be important for racers where seconds could make a difference in a race. But it is unclear how relevant this is to most riders.
So, my question is, if all variables are identical except for the lube, and you rode exactly 10 miles in dry conditions at a given power output (I believe the efficiency test was at 250 watts), how much sooner would you reach 10 miles using paraffin versus ProLink, my current preferred lube?
Here is the answer Jason Smith of Friction Facts, who performed our Velo chain lube test, came up with:
The quick and easy way to answer the question would be to use the analyticalcycling.com (AC) site. Based on the lube test results, at 250W, paraffin consumes 4.82W. ProLink consumes 7.23W, a difference of 2.41W. When using the AC formulas, I’ll plug in 250.00W and 247.59W and look at the difference. Now, this is not exactly the case, since the rider is actually putting out 250W in both cases, and the 5W difference is lost in the drivetrain, but as a place to start, I’m assuming the rider is putting out 2.41 fewer watts in order to use the AC plug-n-play formulas.
250 watts = 25.12 mph; 247.59 watts = 25.03 mph; a difference of 0.09 mph
Now, to perform my calculations, I’d like to look at two scenarios: the two limits of speed difference. Again using 250.00W and 247.59W as rider outputs, assuming the only drag slowing the rider down was purely mechanical (bearings and tire rolling resistance) and no aero drag, then the relationship between mechanical drag and speed would be linear. Therefore the speed difference would be 247.59/250.00 x 25.12 = 24.88 mph; a difference of 0.24 mph.
For a second scenario, assume zero-percent mechanical, and 100-percent aero drag. The relationship between aero drag power and speed is P=1/2V*3. In this case, a 2.41W difference equates to a 0.82W difference when viewed linearly. 249.18/250.00 x 25.12 = 25.04 mph; a difference of 0.08 mph
(Of course, these two scenarios would never happen, but they set up the limits, according to my formulas.)
Now, you’ll note that the AC difference falls between my two scenarios. Since the AC number is pretty close to the 100-percent pure aero scenario, I speculate they are using a high aero ratio when looking at overall contributions of aero versus mechanical drag.
For the next step, I’m going to calculate my own ratios using the data I have available for mechanical drag at 250W output, and 25mph:
Chain and pulleys 8W average
Pedals 0.75W average
Bottom bracket 1W average (not tested yet, but this is where I feel they will be coming in)
Two hubs 4W total (not tested yet, but I feel hubs will be running 1-3W each)
Two tires 60W (30W each). (I’d use your Velo test data, but I can’t find that issue in my pile of Velo mags.)
The total mechanical friction wattage consumption in this case would be approximately 74 watts, and aero wattage would be 176 watts (250-74).
The ratio is approximately 30-70-percent, given this example, at 250W rider output, and 25 mph.
Using this ratio, and using a 0.08 mph to a 0.24 mph bandwidth, knowing the 30-percent mechanical drag is linear, and the 70-percent aero drag is ½ cubed, a 2.41W difference in mechanical friction would amount to a 0.10 mph difference.
And voila, my calculations show 250 watts equals 25.12 mph; 247.59 watts equals 25.02 mph.
To get back to the reader’s question. A 2.41W difference due to chain friction equals a 0.10 mph difference. Over a 10-mile ride, the time difference is 5.73 seconds.
I welcome others of you so motivated to work on this calculation as well. This is considerably more time difference than I would have guessed, and I must admit being dubious.
If this really is the case, it could be a significant difference in a time trial or other individual events.
Campy master link solutions
I’ve been searching for a master link for my Campy 10-speed chain. Does this item exist to your knowledge? Without, it is quite expensive to remove and re-install the chain.
Wippermann makes a Campy-specific 10-speed master link. That said, any 10-speed master link will work; I run Campy 10-speed on both of my cyclocross bikes, with master links. While I have run plenty of non-Campy 10-speed chains on them without problems, I’ve also run Campy chains with Wippermann, KMC, and SRAM master links (for the latter, you need the Park master link pliers to open it since it’s not intended to be opened).