Last updated: January 2nd, 2023
Even with the same level of effort, two bicycles can feel wildly different in speed. It can seem like you’re inching up a gentle slope on one, yet practically flying on another, without consciously working harder.
The latter’s speed is a combination of perception and reality. Some bicycles are objectively faster thanks to improved aerodynamics, reduced weight, and greater mechanical efficiency. But our brains also play tricks on us, and may interpret vibrations, physical feedback, and even looks as speed.
Whether you’re just curious about the physics at play, or you want to upgrade your bike for a faster ride, here’s what makes some bicycles so much faster than others.
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1. Powerful & aerodynamic riding posture
The fastest bikes put the cyclist in a profoundly forward-leaning posture. This is characteristic of most road bikes, and it’s taken to an extreme in the elbows-forward posture of a time trial bike.
That posture isn’t very comfortable, but it serves two purposes at once: minimizing wind resistance and maximizing power from the glutes and calves.
The handlebars are far forward from the saddle, and as low as possible. This pulls the cyclist’s torso down and forward to keep it out of the wind. And with the pedals slightly forward of the saddle, the hips are “hinged” so each pedal stroke begins with the glutes in the most powerful part of their range of motion (akin to crouching down before we jump in the air.) Moreover, this position helps experienced cyclists take advantage of clipless pedals to eke out even more force throughout the pedal stroke.
2. Aerodynamic components minimize drag
The speediest road bikes reflect years of wind tunnel testing to streamline everything from frames and forks down to spokes and brake calipers. The more blade-like their forward surfaces, the less air they “push” against.
Of course, it’s a balance between efficiency and strength, since overly skinny shapes won’t withstand sprints or potholes.
The impact of bicycle aerodynamics matters far less than the rider’s posture. After all, a person is wider and taller, therefore an exponentially greater source of wind resistance. But with prizes and prestige at stakes, racing bike designers aim to leave nothing on the table.
Like all speed tactics, aero design has its trade-offs: chiefly weight and ride quality. Slim, elongated shapes may lose horizontal or torsional strength, which requires added material to make up for. The result is heavier and often less compliant (vibration-dampening) at the same time.
So, while aerodynamics is always a factor in road bike design, not all quick bikes of them are fully “aero.” And in some cases—like an all-day ride with extended climbs—the fastest bike may be one that sacrifices some wind resistance for lighter weight, steadier handling, and less vibration-induced fatigue.
3. Appropriate tires to minimize rolling resistance
Tire choice affects speed as well as mention traction, bump absorption, and overall ride quality. The right rubber strikes a balance between just enough tread and volume to inspire confidence in the worst likely conditions, but not so much as to create unnecessary rolling resistance.
This, of course, is relative to the terrain. The same attributes that slow you down on pavement can speed you up on trails, and vice-versa.
Smooth but porous asphalt is easy to grip, so the very fastest road tires are slick or nearly slick. The oblong contact patch of a bicycle tire isn’t prone to hydroplaning, so siping (tiny slits rather than tread) is adequate for wet streets.
(Racers do use slightly wider tires these days, at around 25mm versus the ~20mm of yesteryear. The extra air volume makes for a smoother and more efficient ride, which helps more than the extra grams of rubber hurts.)
Dirt is soft, prone to shifting, and full of unexpected obstacles, so the fastest mountain bikes tires are often well over 2″ wide and may have deep tread for grip on climbs and confidence in corners. Even staying upright, let alone riding fast, requires a wider, softer tire that digs into and soaks up the terrain.
4. Light weight, especially in the wheels
Newton’s second law tells us that it takes more force (i.e., harder pedaling) to get a heavier object up to the same speed. The less a bicycle weighs, the faster it feels when you’re trying to accelerate. Weight is also a factor when holding a steady speed, but it matters far less by that point.
This effect is especially noticeable in the wheels, which not only move forward, but rotate at the same time. That’s exponentially more net motion, as it were, than static parts like the frame, so the effects of wheel and tire weight are disproportionately significant.
Weight also plays an increasing role on steeper climbs. On flat ground, the surface is perpendicular to the bike’s mass, so it has little impact once up to speed. But point the bike uphill, and the ground only supports a portion of the bike’s mass, so gravity pulls the rest of its mass downhill. The rider has to fight this effect, which grows stronger and the slope grows steeper.
(And you thought those force vectors drawings in physics class wouldn’t be practical!)
Lighter bikes often prove faster on highly technical singletrack, too. When you’ve got to lean, hop, and otherwise manhandle the bike in close quarters, it’s simply easier (therefore smoother and faster) when you’re hauling less mass. Combined with reduced effort to accelerate out of those situations, it’s easy to see why even downhill MTB racers drop big bucks on light bikes.
5. Stiff frames & parts that transmit power
The fastest bikes use strategically stiff frames (especially in the chainstays) to maximize power transmission and minimize loss to bobbing and bouncing.
Elite road cyclists put out upwards of 400 watts for extended periods, and can exceed a staggering 2,000 watts during a sprint. With so much raw power, even a couple percent difference in efficiency can change the outcome of a close race.
The engineering is complicated, but the principle is simple. To give an extreme example, imagine sprinting on the ground versus sprinting on a trampoline. The latter would feel great on your knees and ankles, but your pace would be comically slow.
The same idea applies to components, especially handlebars and stems, since racers also push and pull with their upper bodies to generate even more force at times.
Of course, stiffness requires some compromise. A little bit of “vertical compliance” is necessary to dampen vibrations that would otherwise make the ride more fatiguing and therefore slower. Carbon fiber allows for different degrees of stiffness in different directions, so it’s a supremely useful material for modern racing bicycles.
6. Narrow gear intervals for an efficient cadence
Having more gears doesn’t make a bike quicker, but it does make it easier to maintain the optimal pedaling cadence. That’s around 90 rpm for trained cyclists and 60 rpm for an untrained but generally fit adult. Staying around that cadence means less wasted energy and therefore faster riding over a long period.
For instance, a 9-speed and 12-speed cassette may have similar minimum and maximum gears, but the 12-speed will have smaller steps within that overall range. That means more opportunities to find a gear that allows the rider’s ideal cadence, even as they fatigue and the terrain undulates.
Gear intervals matter less for mountain biking speed. Cadence is still relevant, especially for XC MTB racing, but it’s rare to pedal for long stretches without standing or coasting over obstacles. But gear range is a large concern for MTB racing, since sufficiently low gears make the difference between riding the steepest climbs versus losing time walking them.
7. Suspension brings speed & smoothness off road
Suspension makes mountain bikes faster by helping them maintain momentum over obstacles. This plays out in two main ways.
First, a rigid bike has to rise by roughly the height of each rock and root it rolls over. Suspension accommodates some of that vertical displacement, which lets the rider continue in a smoother path.
Second, it takes the edge off of hard impacts so the rider can maintain a faster, more aggressive line of travel. Even XC race bikes have front or often full suspension these days, since its weight penalty pales in comparison to its speed benefits.
On pavement, it’s another story. Without an onslaught of large obstacles, there are few situations where suspension helps, so its weight penalty is harder to justify. A few gravel bikes do have suspension forks or stems, but they’re nonexistent on road racing bikes.
8. Strong, responsive brakes for confidence at speed
If you’ve ever ridden a public shared bike or low-end rental, then you probably took it a bit easy just in case the brakes didn’t quite perform as expected. Great brakes don’t make bikes faster, but they prevent the need to ride slower just in case.
Consequently, the fastest bikes need powerful brakes with sensitive modulation. That’s not only beneficial for safety at high speeds, but also lets riders carry their high speeds into corners and brake at the last second.
To be sure, brakes alone can’t replace skill and confidence. It takes years of training to get a feel for how to brake less in the first place and how to push brakes to their limit when necessary.
But the need for predictable power in extreme situations is why all types of racing bikes have remarkably powerful brakes. “Powerful” means something very different to road racers versus downhill mountain bikers, but they all help control speed finely and predictably within their intended purpose.
9. Low-friction bearings (and fastidious maintenance)
Sticky, crunchy bearings sap at least a little bit of power. In particular, race bikes use top-of-the-line drivetrain parts that minimize friction, especially in foul weather. This can involve ceramic bearings, cutting-edge lubricants, and any number of expensive innovations that confer a slight edge.
Maintenance is a less glamorous but more important factor. If you’ve ever pulled an old bike out of storage only to find that the pedals barely turn, then you know the long-term effects of neglect. Even a Tour-ready bike will (literally) grind to halt if grime accumulates and lubrication deteriorates unabated.
Perception is reality
All the above can make a bike objectively faster. But more subjectively, we also tend to associate a “lively” ride with a quick one.
It makes sense that our brains associate stronger ground feedback with higher speed. In the context of natural movement—namely walking and running—it’s usually true. A sprint feels harsher than a jog, and it really is faster.
But when machines enter the picture, it’s not that simple. Frames and tires and suspension all mediate ground feedback, so more vibration doesn’t necessarily mean more speed (although it certainly could). For example, new cyclists often convince themselves that skinnier, harder tires are faster. In reality, it only seems that way due to more intense vibrations. In fact, testing suggests that cushier tires (within reason) are actually faster despite a duller feel.
To give a more universal example, you’ve probably experienced driving on an empty freeway in an old beater of a car as well as a new one. Odds are the former transmitted every crack in the road and felt like a rocket taking off at 55 mph, but the latter made 70 mph feel like a silky-smooth cruise.
Visual perception also plays a significant role. According to research published in the Journal of Vision, prolonged travel at high speeds makes us believe we’re going slower than we are. Frequent visual cues, as opposed to wide-open space, also make us feel faster.
If you’re trying to determine whether certain upgrades make you faster, then suffice to say that perception can be misleading.
Summary: why some bikes are faster than others
Riding posture and tire rolling resistance explain most of why one bicycle is faster than another. Secondary factors include bicycle aerodynamics, stiff frames and parts, suspension (on mountain bikes), confidence-inspiring brakes, and state-of-the-art bearings and lubricants.
Perception also plays a large role, since a smoother ride may be objectively faster yet feel slower. If you’re comparing two bikes or trying to wring extra speed out of yours, then don’t rely on feel alone!