How Much Extra Energy Is Consumed by a Dirty Chain?

Making a case for developing a practical chain guard for multi-speed bikes.

I performed tests on several multi-speed bikes to determine how much energy is wasted by a dirty chain.  The results were significant and consistent.  The dirty chains consumed 8 to 12 watts of energy when the power at the crank was tested in a range of energy outputs that would be typical to propel a bike 8 to 14 mph.

What does 8 to 12 watts of lost energy mean when riding a bike?  At 15 miles per hour, a typical bicyclist  will slow down to 14.5 miles per hour if 12 watts of energy is taken away.  This would add about a minute and a half to a 10 mile ride.  On a 4 percent grade at 10 mph, wasting 10 watts of energy is like adding 10 pounds of weight to the bike.

Experiment Design
I used three different bikes that had been ridden anywhere from several weeks to several months since the last cleaning or oiling of the chain.

In each test I used a DC powered electric drill to drive the crank from the spindle bolt.  I measured the motor voltage and amperage at various speeds.   I repeated measurements at each speed a number of times.  I added two tire driven light generators to increase the resistance on the spinning tire in order to simulate the actual resistance of normal riding.  Multiple nicad batteries were used to minimize the voltage drop from the power source.

After measurements were made with a dirty chain, I cleaned the chain, the derailure guide wheels, and the drive gears.  I lubricated the chain with a light oil lubricant.  No other parts of the bike were changed.

I recharged the nicad batteries and carefully repeated the same sequence of speed measurements, again charting the voltage and amperage.

The energy unit of watts can be calculated by multiplying the volts times the amps.  With the tabulated results I could calculate the change in watts.  The error fluctuation in each phase of the measurement was in the range of 2 watts.  The bike chain that looked like it had the least oil showed the biggest improvement, but even a chain that had been oiled within three weeks showed an improvement 8 to 10 watts saved after cleaning and oiling.

Oiling Without Cleaning
On one bike that had not been oiled in several months, I made the "dirty" measurement and then just oiled the chain thoroughly without cleaning.  The freshly oiled "dirty" chain used 10 less watts than the initial measurement.  I then cleaned and oiled the chain as in the other experiments and measured the power consumption again.  The clean chain did not produce a measurable improvement over the freshly oiled "dirty" chain.  This null result is a reflection of the limits of precision in the method and equipment  I used.

Additional Notes
This experiment was limited in precision by several factors.
Conclusions Return to main page