Every cyclist knows the feeling. You're twenty miles into a ride, and that nagging discomfort starts creeping in. By mile fifty, you're shifting constantly, trying to find relief. By mile eighty, you're counting down the minutes until you can get off the saddle.
Most riders blame the saddle itself. They swap one for another, then another, accumulating a graveyard of expensive seats that never quite worked. But the problem isn't the saddle—it's the fit. And the fit starts with a measurement most cyclists have never taken: sit bone width.
What Are Sit Bones, and Why Should You Care?
Your sit bones—technically called ischial tuberosities—are the two bony knobs at the base of your pelvis. They're designed to bear weight when you sit. On a bicycle, these bones should be your primary contact points with the saddle.
When they are, everything works. Your weight is distributed across bone, not soft tissue. Your nerves and arteries remain uncompressed. You can ride for hours without numbness or pain.
When they aren't, problems multiply. The saddle presses into your perineum—the area between your genitals and anus—compressing nerves and blood vessels. The result? Numbness, tingling, saddle sores, and in severe cases, long-term health issues.
The catch is that sit bone spacing varies enormously between individuals. Research shows it ranges from about 100mm to 175mm across the cycling population. Yet most saddles come in just two or three width options. It's like buying shoes that only come in sizes 8 and 10 and expecting everyone to be comfortable.
How to Measure Your Sit Bones at Home
The good news: you don't need expensive equipment or a professional fitter to get started. Here's a simple method that works:
What you'll need:
- A piece of corrugated cardboard or firm memory foam
- A hard, flat surface (like a step or sturdy stool)
- A tape measure
Step-by-step:
- Place the cardboard or foam on the hard surface.
- Sit on it in a position similar to your riding posture—torso slightly forward, feet flat on the floor.
- Press down firmly and hold for about 30 seconds. Your sit bones will create two distinct indentations.
- Stand up and measure the distance between the centers of those indentations.
That number is your sit bone width. But here's where it gets interesting: that measurement is just the starting point.
The position factor: Your sit bone width changes depending on how you're sitting. In an upright position, your weight rests squarely on the ischial tuberosities. But when you lean forward into a riding position, your pelvis rotates, shifting the contact point. For road cycling, experts recommend adding 20-30mm to your measured width to account for this forward lean. For an aggressive aero position, the contact point shifts even further forward to the pubic rami—a different bony structure entirely.
This means the saddle that fits perfectly for a casual Sunday cruise might be completely wrong for a Tuesday night race. And the saddle that works for a century ride might be torture during a time trial.
Why Fixed-Width Saddles Are Fundamentally Limited
This is the problem that the cycling industry has struggled with for decades. Traditional saddles are fixed shapes—they can't adapt to different riding positions, different bodies, or even the same rider on different days.
Consider what happens during a typical long ride. You start fresh, sitting upright. As you warm up and get into a rhythm, you drop into a more aerodynamic position. Later, climbing out of the saddle, you shift your weight forward. On descents, you slide back. Each of these positions changes how your pelvis contacts the saddle.
A fixed-width saddle can only be optimized for one of these positions. Everything else is a compromise.
This is where the adjustable saddle concept changes the game entirely. Rather than forcing riders to choose from a handful of fixed widths, designs like those from Bisaddle allow you to dial in your exact sit bone spacing—and change it as needed. The two halves of the saddle can slide closer together or farther apart, accommodating everything from a narrow aero tuck to a wide, supportive endurance position.
Think of it like having multiple saddles in one. Need a narrower profile for a race? Close the gap. Switching to a relaxed group ride? Open it up for better sit bone support. The same saddle adapts to you, rather than the other way around.
The Health Implications You Can't Ignore
The connection between saddle fit and health is well-documented, yet many cyclists remain unaware of the risks. Research has consistently shown that improper saddle fit can cause serious problems.
A study measuring penile oxygen pressure during cycling found that traditional saddles caused an 82% drop in blood flow. When riders used properly fitted saddles that supported the sit bones, that drop was limited to approximately 20%. The researchers concluded that adequate saddle width to support the sit bones was more important than padding thickness in preserving blood flow.
The mechanism is straightforward. When your sit bones are properly supported, the perineum is relieved of pressure. The pudendal nerve and internal pudendal arteries—which run through the perineum—remain uncompressed. Blood flow continues, nerves remain functional, and the numbness or tingling that signals trouble never appears.
For women, the stakes are equally high. Female cyclists report issues including labial swelling, vulvar pain, and even long-term tissue changes from saddle pressure. A 2023 survey found that nearly 50% of female respondents had experienced long-term genital swelling or asymmetry linked to saddle use.
These aren't rare problems. They're common consequences of a fundamental mismatch between rider anatomy and saddle design.
The Performance Angle: Comfort Equals Speed
There's a persistent myth in cycling that comfort and performance are opposing goals—that to go fast, you must accept discomfort. Nothing could be further from the truth.
When you're comfortable on the saddle, you can maintain your position longer. You're not shifting around every few minutes trying to find relief. You're not losing power because you're bracing against pain. You're not cutting rides short because the discomfort becomes unbearable.
The data backs this up. Studies show that riders who experience saddle discomfort produce less power, particularly over longer durations. The constant micro-adjustments to find relief waste energy and disrupt pedaling efficiency. And the mental toll of enduring pain reduces focus and motivation.
A saddle that properly supports your sit bones isn't just about comfort—it's about performance. When you're not fighting your saddle, you can focus on the road, your technique, and your effort. You can ride longer, harder, and more efficiently.
Practical Steps for Finding Your Perfect Fit
Ready to take your saddle fit seriously? Here's a practical approach:
- Measure your sit bones. Use the cardboard method described above. Do it three times and take the average—your sit bones can vary slightly between measurements.
- Consider your riding style. If you ride multiple disciplines, measure in each position. An endurance road position and an aero triathlon position will likely give different numbers.
- Choose adjustability. A saddle that can adapt to your measurements—and change with them—offers a level of precision that fixed-width saddles cannot match. The ability to fine-tune width for different rides, different positions, and even different days is a game-changer.
- Re-measure periodically. Your body changes. Flexibility improves, body composition shifts, and riding style evolves. What fit six months ago may not fit today. Regular measurement ensures your saddle continues to support your anatomy optimally.
- Listen to your body. Numbness, tingling, or persistent pain are not normal. They're signals that something is wrong. Don't ignore them.
The Bottom Line
Your sit bones are the foundation of your cycling experience. They determine how your weight is distributed, how your soft tissues are protected, and how comfortable you are over long distances. Yet most cyclists never measure them.
The industry is moving toward personalization—custom 3D-printed saddles, pressure-mapping fitting systems, and adjustable designs all point in the same direction. The recognition that riders are unique, and their saddles should be too.
The Bisaddle approach—combining adjustability with ergonomic design—represents a shift in thinking. It's not about finding the one perfect saddle. It's about having a saddle that can be perfect for any ride, any position, any body. And that starts with knowing your sit bones.
