The most common definition of ride quality is “a comfortable ride.” This is accurate — to a point. When you dive into the engineering side of ride quality and comfort the subjects become very complex. After conducting a long-term collaborative study with the University of Sherbrooke, we concluded that despite subjective opinions on what is “more or less comfortable,” there comes into question a stable definition of the term comfort. One of the most compelling findings of the study was that there is no universally accepted definition for the ideas of comfort or of ride quality. In the automotive industry “good” ride quality is defined as the ability to minimize the effects of road irregularities on vehicle passengers. On a bike, however, you are more than a passenger — you are the pilot, navigator and engine — so bicycles are more complex in this regard. All of your physical interactions with the bike, including merely sitting on it, affect your perceptions of the ride.
At Cervélo, we think of ride quality as the feeling of the bike being appropriate for its intended use. The S5 aero road bike, for example, is all about speed – riding as fast as possible on decent paved roads. That’s why we lowered the headtube geometry to permit a more aggressive rider position with even better aerodynamics, and also increased stiffness to aid power transfer and handling. For our C Series endurance road bikes, the intended use is about riding further, or longer, on a wider range of surfaces in potentially inclement weather conditions. In this application we chose a shorter, more upright geometry for the frame, selected tube shapes that prioritized vertical compliance and light weight, and then constructed the frame without using ultra-high modulus (UHM) carbon for a damped ride feel. Together these elements work together to create a unique ride appropriate for endurance athletes.
Many of the pro cyclists who ride Cervélos talk about ride quality in terms of comfort. However, as mentioned above, comfort is very difficult to define and measure. There are a number of academic papers on the subject, and combined with our considerable research, work continues to be conducted in this field. While we aren’t ready to publish a precise definition or formula for comfort itself, we can look at elements that correlate to comfort in two categories: static and dynamic comfort.
Static comfort refers to your perception of the bike when at rest, such as when you are sitting on it on a trainer in the shop. What can be perceived in this situation?
- Perhaps the most obvious element is fit. If you feel overly stretched out or cramped, if you’re unable to reach the brake levers or a water bottle, or if you can’t easily stand over the frame, then you are going to perceive the bike as uncomfortable.
- Next, consider your body’s contact points with the bike: Feet, seat, and hands. Choosing the correct saddle is critical for your riding enjoyment. With your hands, you are not only evaluating the location and shape of the handlebar, you are assessing the effect of the bar tape and any gloves you may be wearing. Likewise, your choice of shoes can significantly impact your feelings even before you get out on the road.
Once touch points have been addressed, there are also issues pertaining to body position. Are the bars too low and causing shoulder, wrist or neck pain? Is the saddle too far back or too high? Studies have shown that comfort is most noticeable when it is absent, or when it can be compared to something else. Further complicating this is the effect of context — your perception of comfort likely changes for the same bike on the same road on a sunny day versus in a driving rainstorm. Or heavy versus light traffic. Or how well you slept, or whether you stretched that day.
Dynamic comfort refers to the experience of the bicycle in motion. This system is enormously complex, but there is one measureable element that does correlate well with perceived comfort: Vertical compliance, which is the deflection (movement) in a vertical plane that can be measured as a response to an input. Simply put, vertical compliance represents the bike’s ability to react to a bump in the road.
When the front wheel contacts the bump, even as you sense the impact in your hands, each of the elements in the system deflect to some degree in response. The components between the bump and your body make up the system. The charts below represent generalized examples for a road bike showing the relative contribution of each component to total compliance:
Note that the impact of the rear wheel on the bump is similar, except the relative contributions change because there are fewer flexible components in the system.
What these charts tell us is where to focus our engineering efforts to best optimize the vertical compliance for a given intended use. And going beyond engineering, we can also choose appropriate components to match.
READ MORE ABOUT RIDE QUALITY IN OUR ENGINEERING FIELD NOTES:
SQUOVAL IPC AND ENDURANCE ROAD BIKES: How Cervélo engineers used Squoval In Plane Compliance tube shapes to design the C Series.
SENSIBLE FRAME FIT: Why does Cervélo use stack and reach to determine fit?
THE MYTH OF MODULUS: My wife’s bike has a decal on the top tube that reads “Super High Modulus,” so I am assuming this refers to the carbon fibre used. My Cervélo R5 doesn’t say anything about the material in any of the literature. Is my wife’s bike better than mine?
INDUSTRY STANDARDS, PART 3: How do bicycle manufacturers measure frame stiffness? Is there an industry standard for comparing it?