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Cumulative Marginal Losses: Pay attention to the details and stop wasting your watts.

To celebrate Dan Bigham's world record this past week I thought we might discuss efficiency a bit and see if we can't all gain a little bit of "free speed" somewhere .......

Pssst. I am 100% sure everyone reading this can!


There is a theory in mechanical engineering called “the perfect machine.” Essentially, a perfect machine is one that operates with 100% efficiency, meaning there is no energy loss through the operation of the machine, but this is only a theory because it is impossible to create a machine of any kind with zero energy loss.

When we think about optimizing a bike setup, we are using the principle of the perfect machine as our guide. We are trying to design the bike, equipment and position for each rider to minimize energy loss along the way and utilize more of the rider's effort to produce propulsion and forward movement.

**Most important, these marginal effects do not just effect the fastest athletes, in fact it is the riders in the middle and back of the pack that often have the most inefficient bike setups and thus stand to gain the most by improving things!

At the end of this post there are 5 simple steps you can take to improve your efficiency!

Think of it this way: if you get on an old rusty beach cruiser bike with fat knobby tires that are not inflated properly and you produce an effort of 300w, much if not most of that 300w YOU are producing is not going to work to propel that bike forward; it is going to work to overcome the inefficiencies created by this less than perfect machine. Some of your watts would go to overcoming rolling resistance of the tires, some to overcoming wind resistance because you are seated so upright, and some to overcoming the drivetrain friction from being so rusty. The remainder is what propels you forward, and thus your speed is incredibly slow.

Now, if we take that same rider (you) and place them on an optimized bike with a clean and efficient drivetrain, properly inflated tires for your given terrain. and an aerodynamic position, you will travel at a much faster rate of speed given the same 300w effort because you are overcoming fewer obstacles.

This idea is commonly called the effect of “cumulative marginal gains”. The idea is that if we optimize lots of small things on the bike and rider, the cumulative effect of those minor improvements becomes a more significant improvement. BUT… if we look at bikes through the lens of the perfect machine, I think it is more important to frame this as “cumulative marginal losses” because it is not that you are getting “free speed,” it is that with every choice to optimize, you are giving up less of the effort YOU ARE PRODUCING!

It is not that these improvements are gaining you anything; it is that you are giving away less.

Why on earth would you want to work so hard to improve your FTP only to ride a bike with a terrible, rusty, sloppy drivetrain and use all that work simply to overcome that friction??

We want to use that effort to move forward faster!

Let's take a quick but incredibly relevant detour we only have to look to this past week when Dan Bigham successfully broke the hour cycling record covering a little bit more than 55km in 60minutes flat. That is 34 miles per hour for 1 hour straight!!

How did Dan do this?

#1. Huge Fitness and training

#2. Eliminating cumulative marginal losses.

By eliminating every possible wasted energy opportunity Dan was able to utilize a higher percentage of his power produced to actually travel forward FASTER!

Here is his bike.

When we think about energy loss we are looking at three significant forces.

#1. Aerodynamics.

The rider makes up the bulk of the resistance on a bike, so position is absolutely critical to minimizing losses, but we also want to consider all of the little inefficiencies: front brake, brake and shifter cables, cycling or tri kit, wheels, helmet and so on. Anything that hits the wind when cycling creates inefficiency and effectively robs you of speed, so the more of these things we can optimize, the faster you will go.

#2. Rolling Resistance

This is the friction created between the bike and the road surface. To improve it, we need to look primarily at tire choice and tire pressure (though everyone out there riding classic butyl inner tubes is losing watts … that simple. Switch to latex and you will minimize a little loss there). Tire choice and tire pressure should be chosen based on the road surface. Generally speaking, the rougher the surface, the bigger the tire and less pressure you want to run.

#3. Mechanical Friction

Mechanical friction is the energy lost and utilized by your drivetrain (the pedals, gears, chain and hubs) . These friction forces are lost watts that do not move you forward.

A dirty chain …. Energy lost.

An old, bad hub or bearing ….Energy lost

Inefficient chain lube…. Energy lost

Chain rubbing on your front derailleur… Energy lost

When you are looking at your bike or thinking “I feel like I should be so much faster on the bike,” think about all the cumulative marginal losses you have in your bike. The list can go on and on and on, but when we optimize for giving away less of our effort to things that don’t create propulsion, we get to use more of our effort to get from A to B faster.

So don’t just hop on your bike and go. Think about how you can get the most out of your body and limit the loss from your machine.!

Here are 5 simple and actionable solutions to the most common marginal loss issues at triathlons.

1. Bad Bike Fit!