Your saddle supports your sit bones - the ends of your pelvic bones that protrude when you sit down.
Your two sit bones or the Ischial Tuberosity
If your bicycle saddle is too narrow then your sit bone or ischial tuberosity will extend over the side of the saddle, placing your weight on the soft tissue of your genitals.
In the figure below, notice how this seat is too narrow. Only 1 of the 2 ischial tuberosities is resting on the seat. As a result, the cyclist is being supported by his pubic or genital region
Saddle Width & Cycling Position
Riding posture has a huge effect on your saddle width and saddle shape. As you go from riding in an upright, cruiser-like posture to an aerodynamic racing posture, your pelvis tilt changes. This alters the interaction of how your sit bones are positioned on your saddle.
As you can see, the riding posture changes the position of the cyclist's pelvis.
While sitting upright, the majority of your weight is supported by the tip of your sit bones. As your pedaling intensity increases and your riding posture drops, your weights shift from the outside of your sit bones to the inside of these bones and also onto your pubic bone.
In the above image, the majority of your weight while sitting upright is placed near the edges of your sit bones. In a dropped, racing posture, the majority of your weight shift to your pubic bone.
All the postures that fall within these two extremes will place your weight somewhere in-between these two contact points.
The more forward-leaning, the narrow the seat needs to be as your inner sit bones or pubic bones support your weight.
Wide cruiser saddle compared to a typical road bicycle saddle
Wide Leisurely Seats
The reason cruiser-style bicycles have large, wide seats, is because the upright posture places the weight on the widest parts of the ischial tuberosities or sit bones.
Narrow Racing Saddles
Narrow racing saddles are narrow, since this aggressive posture places the majority of the rider’s weight on the inside of the sit bones or even further down, onto the pubic bone.
Not only does a racing posture change the saddle width, but also the shape and pressure relief areas (cut-outs)
Signs Your Saddle Is Too Narrow
Pain in the groin region as your delicate areas are supporting your weight as opposed to your ischial tuberosities.
If super narrow, then you will actually be falling off the saddle or will try and sit further back where the saddle is at its widest.
Riding styles & final thought
Bicycle saddle width is based upon the width of your sit bones and also your torso angle, which is determined by your riding style. This is all predicated on the idea that your saddle is positioned correctly, meaning your bike settings are optimal for you and your riding style.
A cyclist who rides
Cruiser bike
Mountain bike
Road racing bicycle
All 3 of these bicycles, even though it’s the same rider, will have DIFFERENT saddles since the torso angle all differ.
Jesse is the Director of Pedal Chile and lives in La Patagonia. Jesse has a Master of Science in Health and Human Performance and a Bachelor of Science in Kinesiology. Hobbies: Mountain biking, bicycle commuting, reading, snowboarding, researching, and sampling yummy craft beers.
Sources & References
Bressel, Eadric, et al. “Influence of Bicycle Seat Pressure on Compression of the Perineum: A MRI Analysis.” Journal of Biomechanics, vol. 40, no. 1, Jan. 2007, pp. 198–202, 10.1016/j.jbiomech.2005.11.017.
Cheung, Stephen S, and Mikel Zabala. Cycling Science. Champaign, Il, Human Kinetics, 2017.
DBCLS, BodyParts3D is made by. “English: Ischial Tuberosity. Shown in Red.” Wikimedia Commons, 16 Feb. 2015, commons.wikimedia.org/wiki/File:Ischial_tuberosity_02-1_posterior_ (Figure 2 - left photo & figure 4).
Lopes, Brian, et al. Mastering Mountain Bike Skills. Champaign (Il) ; Windsor (On) ; Leeds (Ls), Human Kinetics, 2017.
Lukelahood. “English: Outline of Skin and Skeleton of Human Body.” Wikimedia Commons, 28 Dec. 2020, commons.wikimedia.org/wiki/File:Human_body_template.png. (Figure 1).
Moore, Katherine. “How to Choose the Right Bike Saddle for You.” BikeRadar, 3 Sept. 2018, www.bikeradar.com/advice/buyers-guides/how-to-choose-the-best-saddle/.
“Saddle Ergonomics Explained.” SQlab, sqlab-usa.com/pages/saddle-ergonomics-explained.
“Sit Bones Width Measurement and Bike Saddle Selection.” BikeFit, 15 Oct. 2019, blog.bikefit.com/sit-bones-width-measurement-and-bike-saddle-selection/.