Science of Chain Efficiency
What is Drivetrain Efficiency
Drivetrain efficiency is one of the things that gets talked about the most outside of tires and aerodynamics here lately. Every drivetrain has losses so we are really trying to reduce the losses to be as fast as possible. Drivetrain efficiency is the measure of how much power is lost through the drivetrain while riding.
Efficiency is typically measured as a percentage of power transferred or sometimes as a power (W) lost. 99% efficient is something that companies have been long shooting for and even seen some pretty radical projects to try to achieve. The humble bicycle chain is a remarkably efficient component that can often achieve 94-99% efficiency depending on chain, lubricant, conditions, etc.
This means that if you are putting 250w (a common testing input) into the pedals, that would be anywhere from 235-247.5w making it to the tire. This 12w range would be when the chain is in good condition, clean, and lubricated. 12w is a massive difference at this type of input and can get much worse when the chain is dirty or the lubricant breaks down. Most of the time we are looking at a much smaller difference, especially if you are considering options between top lubricants.
How Does Chain Lubrication Impact Efficiency
Chain lubricant is the thing you can do with the biggest impact to drivetrain efficiency. This is because the friction that drives efficiency down is the metal on metal contact between the inner and outer plates. When the chain articulates around the cogs or chainrings, particularly when the chain isn't in an ideal chain line, this can cause the metal to be sliding against metal and drastically dropping the efficiency of the drivetrain.
Lubricants are working to stop this metal on metal contact through various different strategies.
How does wet lube work?
Wet lube works by using a base oil and often some friction modifiers to stay between the inner and outer plates stopping this friction. One of the easiest ways to rate the efficiency of a wet lube is by looking at its film strength. The better the film strength, the more likely the oil is not going to be pushed out of the space between the plates when exposed to the pressure of riding the bike.
How Does Dry Lube Work?
In short, "dry lube" just doesn't work. This is down to the makeup of the lubricant itself. It is attempting to use the friction modifiers (typically PTFE) carried by something with a very fast flash time like a Naptha or Acetone. The idea is that these liquids would flush out any dirt/debris and leave behind a "low-friction" powder to stop the metal on metal contact. It works great in theory, but test after test confirms that it just fails to work.
How do Wax Lubricants Work
Wax looks to achieve the same goal as wet and dry lubes, which is to keep the metal surfaces apart. It goes about it in a completely different way. Wax is a solid lubricant meaning that when it dries, it fills the gaps in the metal with the wax blend and whatever friction modifiers are contained in the wax. This essentially makes the two surfaces rubbing against each other a highly efficient wax and friction modifier like WS2 that SILCA uses.
This solid lubricant has different limitations where it will eventually be abraded away by debris and the metal itself but as long as there is wax, it will be the most efficient lubricant on the market. This solid nature of the lubricant also is what gives it the cleanliness people have come to know and love. If the chain is full of a solid wax, there is no room for dirt and debris to be worked into the chain.
You can see in the video below that the chain is capable of moving quite a bit while in use. All of this movement is something that will result in metal on metal friction that can be reduced with proper lubrication. Oils can get in there but also will bring dirt with them. Wax can fill those gaps which makes it feel stiff when not in use, but under load, it is a highly efficient and lubricious surface.
How Can You Measure Chain Performance?
There are a few ways to measure chain performance. They each have their own pros and cons, here at SILCA we use all three to help develop our own lubricant products.
1. Lab Testing - On highly calibrated laboratory equipment we can isolate a chain's lubricant and determine the percentage of power being lost at various inputs.
2. Chain Wear Testing - This is commonly used as a proxy for efficiency because it is much easier to measure. Not everybody (almost nobody) has the equipment required to measure efficiency, but wear is simple to measure. Zerofrictioncycling.com is a perfect example of this and can be a very reliable procedure. The flaw with this method is that it is possible to make a lubricant that is very thick and inefficient but reduces wear.
On the contrary it is not possible to make a highly efficient lubricant with very fast wear. This is because the wear comes from metal on metal contact that is inherently inefficient. It is an important test, but certainly far from the only test we should use.
3. Real World Testing - There are a few things you can do with real world testing like the Chung Method to determine drivetrain efficiency. The thing we find most helpful here is that the real world testing is the best way to confirm single application longevity in different conditions as it relates to noise. Sometimes chains can get a little noisy while retaining efficiency, but it doesn't mean you want them on your bike.
Chains should be an afterthought while on your ride and we like to use real world testing to confirm how long somebody should expect their lubricant to last before it starts to be irritating.
What are the Best Practices to Maximize Drivetrain Efficiency?
The most important things you can do to have the highest possible drivetrain efficiency are luckily pretty easy. Choosing a good quality lubricant is the key first step. This will help make everything else work much better.
Secondly, or maybe event the biggest factor, is to keep your drivetrain clean. Dirt and debris in your chain can take a chain that might be losing 3-4w to 15-20w which means it will not only be slower, it will wear really quickly and be extremely loud.
Gearing choice also plays a major factor. Bigger gears are more efficient than smaller gears because the chain articulates less severely at the back. This is a balancing act with chain line. If you have a 60t chain ring that means you need to be in the 28t cog, any efficiency you are gaining by the smaller articulation angle, you are giving up and then some because of the cross-chaining effect. Trying to find a gear where you are mostly in the middle of the cassette is idea.
SILCA has plenty of options to help you with the first two. We have some of the top performing lubricants on the market, as well as cleaners that will ensure any drivetrain can be cleaned well.
What Is The Science Behind SILCA's Chain Lubes?
Science is always first at SILCA. We have worked for years with Purdue University to develop a testing machine, procedure, and development of the best waxes and oils on the market. While most companies are choosing a wax that they think might work well, or copying what they think others might be doing, we started by developing a test matrix with hundreds of different waxes and hybrid blends, then moving to looking at additive packages. The additive packages can make a measurable impact, but will never be able to make up for the lack of an effective base wax.
It is always great to see the independent tests rank SILCA products at the top of their respective categories, but we know there are always gains to be had. They can be in the form of outright speed and efficiency, ease of application, longevity, or any number of other factors. We are committed to never settling and always doing the R&D to bring the most advanced products to the market.
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