How RockShox Rudy XPLR Smooths Your Ride | How Zipp 101 XPLR Smooths Your Ride | More Research about Effect of Vibration Loss to Cyclists
Data shows watt savings when using RockShox Rudy and ZIPP 101 XPLR Wheels on gravel
Cyclists who venture onto gravel sooner or later experience an enemy they may or may not know by name: Vibration Loss. It could be washboards, stones, bumps, or ruts. Vibration loss saps strength and speed—it’s one of the primary reasons three hours on the pavement is nowhere near as rigorous as three hours on gravel (in all its forms). Think of the cobbles of Paris-Roubaix shaking the strength and speed out of pro racers, as an extreme example.
Zipp’s Total System Efficiency (TSE) approach to wheel design focuses on Vibration Loss as one of the Four Barriers to Speed, including Wind Resistance, Rolling Resistance, and Gravity. Vibration Loss is especially devastating to performance in gravel riding because of the constant damage to the rider from riding rough and often varied terrain.
With the XPLR collection, RockShox and Zipp engineers sought to arm gravel riders with a “magic carpet” to smooth out the vibrations slowing them down. Recent research in the SRAM Indianapolis test lab revealed the unique watt-saving combo of Zipp’s 101 XPLR wheelset and RockShox Rudy XPLR fork.
Testing concluded that a rider using the Zipp 101 and RockShox Rudy combination saved almost 16 watts at 18 mph (29 kph) on simulated moderately-rough gravel compared with a baseline carbon wheel and rigid fork. At 13 mph (21 kph), the watt savings was almost 8 watts. A rider using Zipp 101 or RockShox Rudy alone also saved watts, but several watts less than when used together.
As the speeds go up, the vibration is worse. The XPLR components damp more of that vibration out, which means it takes fewer watts than the baseline wheel and rigid fork to hold the same speed.
–Brian Leathers, Test Engineer
Throughout a long gravel ride or race, those savings can help preserve rider energy, allowing for increased speed. The test was conducted at two speeds, 13 and 18 mph, to simulate speeds typical to gravel riders of different abilities. To complete the test, SRAM testing staff first rode sections of gravel roads in Brown County, Indiana.
“We were basing it more on the gravel that we ride south of Indianapolis, where you get into some chunkier spots,” Leathers said. “Test rider subjective feedback got us to the point where we said, ‘OK, we’re representing moderate gravel. We chose that instead of smooth or rough gravel because we wanted to pick something that maybe more riders would experience instead of riding just giant rocks on the side of a mountain or just pea gravel and dust. We wanted to pick something most people would encounter.”
From there, SRAM test staff sought to duplicate the sequence of bumps on the Zipp RollingRoad bicycle treadmill in the Indy test lab. The RollingRoad allows engineers to affix up to 87 plastic slats of various sizes to simulate everything from cobblestones to potholes. The test rider, wearing a safety harness, rides on the RollingRoad like a set of old-fashioned rollers. Engineers then study high-speed video footage and power meter data from riders on the RollingRoad.
Why not just test outdoors on gravel roads? In a lab environment, the RollingRoad allows engineers to dig in, eliminate external factors (like wind) and isolate all aspects related to Vibration Loss.
The 101 and Rudy XPLR each affect ride quality in different ways, creating a powerful combination.
How RockShox Rudy XPLR Smooths Your Ride
It may seem obvious that adding suspension to an off-road bike will increase your level of comfort, but it might be less obvious to say that extra bit of comfort has proven to decrease fatigue and increase rider stamina.
When encountering uneven ground on a rigid bike, vibrations from rocks, pebbles, and broken-up pavement first enter the tire and wheel combination, which, when riding 101 XPLR wheels, absorb and release a lot of those vibrations. However, there are always obstacles a gravel rider can encounter that have a greater impact than what your wheel and tire combination can absorb.
Rudy is RockShox’s answer to long days on varying levels of gravel. Rudy absorbs vibrations from gravel, rocks, and washboard, saving your arms and your control over the bike when hitting larger objects and ensuring the front wheel doesn’t deflect off sudden hits. Smoothing out your ride doesn’t just mean added comfort but a more efficient ride. Every obstacle your bike encounters can be viewed as a “momentum stopper”—small bumps or rocks that slowly eat at momentum over time, meaning riders need to push harder to maintain speed. Larger obstacles have a more pronounced effect—halting velocity or causing the wheel to deflect, leading to a loss of traction, control, and speed, ultimately requiring the rider to put more effort in to regain momentum.
Adding Rudy’s 30 or 40 mm of suspension soaks up vibrations from light to heavy gravel, so your arms and hands don’t have to. Not only do those momentum stoppers cause speed loss, but they also send vibrations up from the wheel, through your fork and into your hands. All those vibrations can lead to arm pump—the overstressing of muscles in the arms causing fatigue, lack of strength, and pain. Rudy’s Solo Air spring is tuned for shorter travel forks to be efficient over bumps and needs only 5 percent sag to be effective.
In summary, Rudy was developed to maintain efficiency while absorbing those vibrations before they reach your hands, not just a softer ride. Tuned for gravel riding, the Rudy Ultimate Race Day Damper also has a true lockout, so you can put the power down when you need it.
How Zipp 101 XPLR Smooths Your Ride
The 101 XPLR is Zipp’s first purpose-built wheelset for gravel. The wheel features a single-wall approach resulting in what we call MOTO Technology. The design allows the 101 XPLR’s rim to “pivot” from either side of the spoke bed while traversing rough terrain. As the wheel encounters obstacles, each edge of the rim offers compliance, creating the feel of extra suspension. For the rider, that means durability and control for greater speed.
Zipp calls this effect “ankle compliance.” Imagine a runner rounding a sharp turn, the ankle naturally flexing to maintain grip as the runner leans. The rim can locally flex to stay parallel to the ground during cornering, which increases traction much like a human ankle. This ability to twist locally allows it to deflect during single bead impacts without the rider getting bounced offline.
Zipp's engineers also designed 101 XPLR to include radial compliance, so the system acts as a shock absorber when you hit rough terrain. Zipp's MOTO Technology allows the rim to flex, which absorbs the impact energy and spreads it away from the impact zone for increased durability. In essence, more of the rim carries the load from the impact.
More Research about Effect of Vibration Loss to Cyclists
Vibration Loss is an often-overlooked performance hurdle for cyclists. It is power loss created by vibrations from the road, which induce a vertical motion on both the bike and rider. When the surface becomes rougher, the effect is more prevalent. “Extra energy is required to lift the entire rider-bicycle mass over even millimeters-tall obstacles in the road texture,” said Zipp Advanced Development Engineer David Morse.
SRAM is not alone in focusing on Vibration Loss' effect on cycling performance. In a 2020 study published in Medicine & Science in Sports & Exercise, researchers from the German Sport University Cologne’s Institute of Biomechanics and Orthopedics sought to understand how surface-induced vibrations in cycling interfered with short-term neuromuscular performance.
The study used 30 trained cyclists on a vibration test setup, including vibration plates at the front and rear dropouts and utilizing sensors on the rider to gauge muscle stimulation. It concluded that while riders can mostly plow through rough roads, they pay a price. "Vibration is a full-body phenomenon. However, the impact of vibration on propulsion is limited as the main propulsive muscles at the thigh are not majorly affected. The demands on the cardiopulmonary and respiratory system increased slightly in the presence of vibration." - Medicine & Science in Sports & Exercise: May 2021 - Volume 53 - Issue 5
The researchers also emphasized the importance of Vibration Loss for racers: “In the context of a cycling race, an increase in heart rate and oxygen demand with vibration indicates a performance loss on cobblestones, although the mainly propulsion-relevant muscles only partially responded to vibration."
Compared with low-intensity recreational cycling, vibration exposure and the response of the propulsive muscles are more pronounced at high cranking power levels as they occur in racing.
–Medicine & Science in Sports & Exercise: May 2021 - Volume 53 - Issue 5
Whether you ride gravel with Rudy, 101 XPLR, or—better yet—both together, the data shows that you save wattage, keeping fatigue at bay for longer.
While the science is complex, the goal is simple: Damp out those bad vibrations.
The test on the RollingRoad featured an elite cyclist riding a gravel bike equipped with a power meter and four different setups: 1) baseline carbon wheel and rigid fork, 2) Zipp 101 with rigid fork, 3) baseline carbon with RockShox Rudy, or 4) the 101 with RockShox Rudy. Each run on the RollingRoad was 2 minutes at either 13 or 18 mph. Tire pressure was set using the SRAM AXS Zipp Tire Pressure Guide. Air Spring pressure was set using the air chart included on Rudy’s lower leg, and Rebound was set in the middle of the range.
Photos by Mike Emery and Kevin Sparrow. Words by Daniel Lee and Sarah Walter.