Today I’m tackling a purely technical performance issue: the chain. I posted a link on Twitter some time ago following a discussion with Julien Pinot about hardware optimizations. The friction-facts site highlights gains of 3 watts between different new Loss of efficiency chains.
I wanted to see if I could personally observe a difference between a new and used car of 5,000 km. The idea is to use the SRM as a benchmark and a G3 power tap to measure the losses. These are estimated at around 3% due to friction on a new car.
What about on a used car?
My last change was at the beginning of September and fax lists having done a good 5000 km since then in rather wintry Loss of efficiency conditions, it was time to change it. My measuring tool confirmed this without detecting extreme wear (elongation at 0.75%: change recommended but not yet mandatory!).
By measuring the power between SRM and PowerTap before and immediately after the change, I wanted to know if there was a measurable gain in efficiency. In short, fewer watts dissipated between the two measurement methods.
For this I had carried out a measurement on the road with about ten passages of 3 min towards 230w on 50*17@85tr/Min then another with a Salbert climb of 12 min towards 280 w on 36*19@85tr/Min. I specify that the two chains were degreased and cleaned with the same product. I added to this a confrontation of the 2 Salbert climbs with the theoretical calculator AWSOFT as onmy wheel tests . The tests took place on dry roads and with temperatures between 5 and 9 degrees.
The results seem to show a difference of 1% to 1.5% loss measured at the powertap wheel between old chain and new.
Comparing the theoretical calculation of the Salbert climb
The SRM measurement (288w before then 285w after), we are not far advantages of combining data-driven from this result. The other information that can be drawn from it, even if the small number of measurements does not allow us to affirm it, is that the efficiency seems better on a large chainring. Indeed, in the available studies, it is advised, while trying book your list not to cross the chain too much, to stay on the large sprockets/chainrings. For example, it will be better to choose 50*21 than 36*16 for a desired ratio of 2.3.