On a Roll: Advice for Better Rolling Resistance and Beyond
As cyclists, we are always looking for that next thing that will make us faster. Whether it’s that new piece of equipment, a new training technique, or a new dietary trend, we all chase that illusive magic speed bullet. With all of these magic bullets flying around, our sport is full of buzz words. One of these buzz words that has become a topic of choice for many cyclists is rolling resistance. However, it is also one of the most misunderstood and hazy concepts frequently discussed in cycling. Often, anything that adds resistance and slows a bike down is lumped into the category of “rolling resistance”. However, there are many more factors at play in the speed and resistance equation. So, let’s get things straightened out and help you better understand how to lower your resistance, make your wattage count, and make yourself that little bit faster.
Types of resistance
Not all resistance is created equal when it comes to cycling. Though it may seem like it would all be rolling resistance, the resistance equation is actually made up of four different factors.
Being aerodynamic (or “aero”) is another buzz word that we often hear around the cycling community. Along with rolling resistance, it is perhaps the one that cyclists think of the most. Simply put, aerodynamic resistance is the drag caused when air comes in contact with your body, bike, and equipment. There are several things that can reduce this, which we will get into later in the article. However, it should be noted that this type of resistance typically makes up 40-50% of the resistance losses suffered by the average road cyclist while riding, far more than what is lost to rolling resistance.
Making up 10-15% of the resistance loss suffered by the average cyclist, rolling resistance is the friction of your tires on the road. While things like tread pattern can affect this, it is primarily a result of the amount a tire deforms when it comes in contact with the road under the weight of a rider. The amount of deformation is changed by a few factors, which we will discuss further down the page.
Gravitational Resistance (AKA Weight)
We all know the cyclist who is constantly striving for the lightest possible bike. Weight is an interesting element of the equation because it actually affects other elements of the equation as well. As we saw from the previous paragraph, rolling resistance is the deformation of a tire under weight. So, the amount of weight the tire is under directly affects the amount of deformation. What may surprise many people, though, is that weight does not make up as much of the equation as aerodynamic resistance. Gravitational resistance accounts for anywhere from 25-35% of the resistance losses suffered by a cyclist.
Perhaps the most overlooked source of resistance when cycling is mechanical resistance. Mechanical resistance comes from metal parts rubbing together in your drive train and wheel hubs. Most people don’t think of mechanical resistance, because it happens in the parts that we don’t pay attention to until they break. The reason this is important, is that it makes up nearly as much of the percentage of resistance loss as rolling resistance, which gets all the attention.
How to Reduce Resistance
Now that we know all of the possible sources of resistance loss when riding our bikes, lets look at ways in which we can reduce those losses and ride faster and more efficiently. We’ll go through a few options that will get you resistance savings and where those savings come from. While a new bike that is either lighter or more aerodynamic might make a difference, we’re going to assume that you’re not in the market for a new bike and are, instead, trying to get the most savings possible with your current bike.
Body Position and Weight (the freebies)
Let’s start with some suggestions that don’t have to involve you spending any money whatsoever. The first is your position on the bike. When watching elite level riders, you will notice one thing in common: they are all positioned low on the bike. By lowering your torso, you create less surface area for the air to come in contact with and push against and, in turn, create less aerodynamic drag. The first step in this is really working on your posture. Make sure your back is straight rather than arched. Bend your elbows, and keep a nice relaxed grip on the bars. If you would like to achieve even greater gains, schedule a bike fit with your local bike shop, and they can help set up your bike in a way to get you in a better position.
The second part of this equation is your body weight. Let’s get this out of the way right now: I am not telling you that you need to lose weight to be faster on the bike! While the numbers may seem to say so, being at a healthy weight is always more important than shedding a few grams. If you feel that your weight is unhealthy and would like to lose some for health reasons, cycling is a fantastic way to do so. However, don’t feel like you have to lose weight in order to be a good cyclist. Even among professional cyclists, each one balances their weight with what their cycling strengths are. Professional sprinters are traditionally far heavier than climbers due to the added muscle.
Quality Carbon Wheels
The change that will give you the most gains in the most places when it comes to resistance loss is a good quality set of carbon wheels. However, not all carbon wheels are created equal, so here are some things to look for and how they make a difference to your resistance gains.
First is the shape of the rim. Each company has a slightly different (or in some cases drastically different) shape or profile to their wheels. These are used to change the way air interacts with the wheel and reduce the aerodynamic resistance. Given that aerodynamic resistance is the largest portion of resistance loss, this becomes very important. A rim that is 50-90mm in depth, often called “deep section”, slices through the air like a blade by reducing the turbulence caused as air comes around the back side of the tire. However, these wheels come at a trade-off. While the cut through the air nicely front too back, winds coming from the side can exert stronger and stronger force on the rider the deeper the rim. So, judge accordingly in your wheel choice based on the area in which you live and the type of riding you do. The other trade off that comes with deeper rims is added weight, which brings us to your next benefit.
Aside from aerodynamic gains, the biggest benefit to a quality set of carbon wheels in the savings in weight. In many cases, carbon wheels are 30-50% lighter than their aluminium alloy equivalents. With 30mm rims, carbon sets often save hundreds of grams, while 50mm aluminium wheels would be so heavy as to be impractical, so they are not even manufactured. This weight savings paired with the aerodynamic savings would make this upgrade worth it on their own. However, there is one more benefit to a quality set of wheels that is often overlooked.
The final resistance reduction that can be gained from a set of quality carbon wheels is in mechanical resistance. Because wheel hubs utilize bearings to spin the wheel, the friction within these bearings is one of the most overlooked sources of resistance loss on a bike. The key with this savings, though, is finding a wheel that uses quality bearings that have the least resistance possible. Most wheel sets on the market utilize standard quality steel alloy bearings because the companies themselves overlook the resistance losses here as well. However, some of the top wheel set manufacturers on the market either offer bearing upgrade options or come stock with low friction bearings. At Hawk Racing, we use the same industry leading low friction bearings from our bottom brackets in our wheels in order to give you the same level of performance in our wheels as you have come to expect in our bottom brackets.
Tire and Tube Choice
This topic could fill many many blog posts in and of itself. The amount of research that has been done on this topic is staggering. However, there are a few guidelines that we can sum up here. First, when it comes to tube choice, latex and lightweight tubes will save you weight and rolling resistance, but at the cost of a greater likelihood of pinch flats. Second, when it comes to tread pattern choice, smoother tires or tires with chevron patterning have the lowest rolling resistance, though that lack of significant tread does come at the cost of some traction. Third, the trend recently has started to tip toward wider tires, which put more tire surface on the road and absorb more bumps. While these tires do have a slightly higher rolling resistance on perfectly smooth laboratory roads, they have proven to be faster on average to poor road conditions because they absorb bumps and keep the tire in contact with the road, thus reducing the loss of momentum bumps typically cause. Lastly, recent research has shown that, similarly to the difference between laboratory and real world conditions with tire width, tire pressure acts the same way. Though a higher pressure may produce a lower rolling resistance in laboratory conditions, a slightly lower pressure that allows the tire to absorb road conditions produces a faster time due to continued contact with the road.
Our friends at GCN produced a fantastic video that sums all of this up and explains it very nicely, which you can find here.
Drive Train Upgrades and Maintenance
Every watt of power that you put into your bike goes through your drive train. However, due to friction within your drive train, some of this power gets lost in overcoming that friction and making the drive train move. That power loss is call mechanical resistance. There are a few sources of it within the drive train, so lets see how we can solve each one. The first and most basic of them is the contact between the chain and the cassette and chain rings. This is the easiest of any of them to solve, as all it requires is that you keep your chain clean and well lubricated. There are many different lube technologies out there, and each has its own pros and cons. So, shop around and find what fits your personal needs best.
The next source of friction in the drive train is the bottom bracket. This is perhaps the least thought of part on a bike, but it can make one of the biggest impacts on drive train friction. As with wheel hub bearings, many bottom bracket manufacturers make bottom brackets using standard steel bearings that create large amounts of friction as they spin. Many of these bottom brackets lose 2 watts or more per revolution of the pedals. While this may not seem like much, 2 watts can create a 1-2 second difference on a 3 mile time trial, which can be several places and may cost you a place on the podium. The industry solution to this has traditionally been ceramic bearings. However, these bring with them an entire set of problems that recent research has shown may not, in fact, make them a better solution. While we won’t get into all of those specifics here, you can read more information here, and see the full study details here. The Hawk Racing solution to this problem was to use high quality aerospace grade steel in our bearings. This allows them so lose a fraction of a watt per revolution, thus putting more of your power toward moving you forward.
The last piece of the drive train puzzle is the derailleur pulley wheels. This can be an inexpensive upgrade that can save you a little bit of extra wattage once the rest of the upgrades have been made. Most stock pulley wheels use bushings rather than bearings to make them spin. This is a very cheap, but high friction solution. After market pulley wheels, such as the ones made by Hawk Racing, use low friction bearings that provide a much smoother solution and saves you that last little bit of power that you can spend on a faster performance.
We’re all looking for better performance. It’s a fact of being an athlete. However, being smart and taking advantage of every available source of resistance savings will serve you much better than the latest trend you may hear about at your next group ride or race. So, do you research and use the tips discussed here, and you will see your times improve, your power be used more efficiently, and your experience on the bike get even better. Enjoy the ride friends.