The rules in a nutshell

These four and a half rules have helped many riders improve the comfort of their saddles. First, if you choose a saddle that’s wide enough to support your sit bones, and second, it’s flat enough (side to side) that it doesn’t wedge up in the middle and flat enough (front to back) that you don’t slide forward; third, firm enough that you don’t sink in and squish the saddle’s padding up too much in the middle, and fourth, decide whether you need a cutout or not, and finally, consider how “T” or “pear” shaped you prefer, then you’re probably most of the way to enjoying riding your bike in better comfort. You could stop reading here, install such a saddle on your bike, and ride happily. But if you want to understand why, then read on.

Rule #1: Wide enough

First, the saddle should be wide enough to support your ischial tuberosities (sit bones). If it’s not, then your body weight is supported by the body parts between them – primarily the labia (in women) and internal penis (in men). This is the main goal: move pressure from the middle to the sit bones. Why the sit bones? The flesh surrounding the sit bones is mainly muscle and fat. Time in the saddle will condition this tissue to the job of supporting the weight, and comfort improves. On the other hand, the tissue between the sit bones contains many nerves and blood vessels, and over time, sitting on it can reduce blood flow (Schwarzer, 2002), cause numbness and sometimes permanent nerve damage (Weiss, 1994), reducing the duration of erections in men (Shrader, 200) and reducing tactile sensitivity in both men and women. For women especially, too much pressure on the soft tissue under the pubic bone can be immediately painful.  To avoid this, reduce or eliminate pressure in the middle. A saddle that’s wide enough is the first step.

Figure 4 Exaggerated illustration of a pelvis on a saddle that’s too narrow (left) and a saddle that’s wide enough to support the sit bones (right). 

Saddle width rule of thumb

How wide is wide enough? Remember the idea is to support the sit bones. One rule of thumb is that the saddle’s seating surface should be equal or greater than the center-to-center spacing between your sit bones, plus about 1 centimeter on each side. 

Saddle width >= sit bone spacing + 2cm

You can measure your sit bone spacing in several ways.

Many bike shops have “assometers” (provided by Bontrager, Specialized or others). These are cushioned sit bone measuring devices that you sit on. Your sit bones leave impressions in the cushion.  You measure the center-to-center distance between impressions.

You can do the same thing at home if you are careful:

• with a piece of Corrugated cardboard which also takes impressions if done right
• By sitting on Playdoh between sheets of paper
• Direct measurement with a ruler or tape measure (and a very good friend)
• Floral foam in a plastic bag

Take your sit bone spacing measurement a few times until you’re comfortable you’ve got it accurate within a few millimeters. Add 20mm. Compare it to the width of the usable seating area of your saddle and any saddle you’re considering trying.

By the way, sit bone spacing has been measured for large populations. This data leads to the following statistical ranges:

Table 1 Ischial tuberostiy spacing among men and women (PeopleSize 1998, http://www.openerg.com/)

The table above lists the distances between ischial tuberosities expected in men and women based on statistical analysis of large-population data. Once you know your sit bone spacing, you can see if you’re in the narrow, medium or wide range of the population. This may suggest you try narrower, average or wider saddles. For many folks who are not average, knowing they are wide or narrow really speeds up saddle selection.

A table of numbers works for some people, but if you’re more the visual type, then the following illustration of the same data may help.

Figure 5 Ischial tuberosity spacing among men and women. A 50^th percentile male pelvis is shown, with ischial tuberosity spacing of approximately 118mm.

In the figure above you can see a sketch of a male pelvis with two bell curves superimposed on it. One ischial tuberosity is fixed at the origin (left end of the horizontal axis), and the bell curves represent where the other ischial tuberosty (right side of the image) would fall, assuming a normal distribution of ischial tuberosity spacing among men (red) and women (blue).

This data shows that, on average, men have about 1 centimeter narrower sit bone spacing than women. This may suggest one possible reason that, on average, women have more saddle issues than men. This data also shows that, between the 5^th and 95^th percentiles, as groups both men and women vary by over 3 centimeters. So statistically speaking, there is roughly three times more variation within each gender than there is variation between the two genders. (That might partly explain why quite a few women are comfortable riding “men’s” saddles, and suggests that some men could consider riding “women’s” saddles.) But these are just stats; you aren’t a statistic and you’ll want to know your individual sit bone spacing to choose the right saddle for you.

But not too wide?

What happens if the saddle’s more than 2cm wider than sit bone spacing? With generally typical road bike riding position and saddle designs, maybe a little more rubbing on the inner thighs, a little extra pressure on the hamstring insertion, but there is usually not too much down side.

On some saddle designs you need more than 2cm extra width. Brooks and similar leather saddles are constructed with a rigid steel cantle plate supporting the perimeter of the leather top; you don’t want to sit on the cantle plate, so consider the area between the edges of the cantle plate the effective seating surface, and measure there.

Overall, too narrow is typically worse than too wide.

Rule #2: Flat enough

Once a saddle is wide enough, it should also be flat enough. If the saddle has too much side to side curvature then the center is significantly higher than the sides. Too much curvature in this way means the center of the saddle is more likely to pressurize the soft tissue below the pubic bone. As mentioned earlier, too much pressure in the middle is uncomfortable for many riders. Almost all saddles have rear view curvature to a degree, so compare several to find saddles that are less curved. 

Figure 6 Exaggerated illustration showing a highly curved saddle (left) and a flatter saddle (right). You can see the curved saddle decreases clearance under the pubic bone compared the increased clearance on the flatter saddle.

But not too flat?

Perfectly flat isn’t necessarily bad here, although with very flat saddles some cyclists miss the “centered” feeling that keeps the pelvis from moving much laterally on the surface of the saddle. Even concave isn’t bad if you’d really rather remove contact between the center of the saddle and your body. (You know if this is you: even slight pressure can be painful.) A flattish saddle with a large cutout is sort of concave anyway if you think about it.

Rule #3: Firm enough

Once a saddle is wide enough and flat enough, it should also be firm enough. Saddle padding shouldn’t be excessively thick or soft, despite the overstuffed “gel” saddles often suggested to beginning cyclists. Thick, soft padding may initially seem like the obvious solution to saddle discomfort, but usually the squishy saddle just squishes down under the sit bones – and squishes up in the middle – adding pressure where you don’t want it. 

Figure 7 Exaggerated illustration showing a highly padded saddle (left) and a firmer saddle (right). You can see the overpadded saddle decreases the clearance under the pubic bone compared to the increase in clearance on the firmer saddle.

Often new riders quit riding after replacing uncomfortable saddles with thick, soft saddles that are also uncomfortable. Instead, choose the firmest saddle you can stand. Often more expensive saddles have firmer padding, but not always. Look around at different price points to find saddles that are firm.

But not too firm?

Is there such a thing as too firm? Some rigid carbon fiber saddles have no padding, and some riders (some men and some women) are perfectly happy with them. Can you be one of them? A saddle with no padding certainly eliminates the “padding squishing up in the middle” issue.  If you like, consider trying one (ideally one that meets the other rules, wide enough and flat enough). Initially you might feel some pain around your sit bones, but some of this will go away as the flesh around your sit bones tones up with use and time. If after a few weeks you still feel like you’re bruising the flesh surrounding your sit bones then a very hard saddle might be too firm.

Rule #4: Maybe a cutout

Even on a saddle that’s wide enough, flat enough and firm enough, some people just need a cutout, or a hole through the saddle. If you have a saddle that’s wide enough, flat enough and firm enough and it’s still uncomfortably pressing on the soft tissue under your pubic bone, then you may need a cutout. 

Figure 8 Saddle with a cutout (left) and saddle without a cutout (right)

One informal “cutout test” is described below. (This test was developed by Kaja Rudinow, a physical therapist's assistant at the Polyclinic in Seattle, WA. It was originally posted in a thread on saddle fit at http://forums.teamestrogen.com. Click here for the original post.)

The cutout test

Find a wooden chair or stone bench or other very hard and unyielding seating surface.

Sit on it.

Hinge forward at your hips (don't bend your back) until you can rest your elbows on your knees.

Stay that way for a few minutes.

If your "soft tissues" object to this treatment, it is likely you would benefit from a saddle with a cutout.

If your "soft tissues" (we're talking labia here, ok?) have no extraordinary issues, it is likely that a cutout is unnecessary, and you might end up being one of the folks who complains about the rubbing or pinching of the edges of the cut-out. (more trouble than it is worth)

Nothing is written in stone, ever. But it's helpful to know a bit about tissue volume. Soft tissue complaints during the test should be taken seriously.

Some saddles are available in versions with or without a cutout (Selle Italia saddles are often available this way). On the other hand, some saddle companies seem philosophically wedded to either having a cutout (Specialized, Terry) or not (Bontrager, Fizik). Because of this, if you need (or don’t need) a cutout, you might consider switching brands.

Or maybe not

Is there a downside to having a cutout if you don’t “need” it? Often, there is no downside, and many people who don’t need a cutout happily ride saddles with cutouts. But some cutouts increase pressure on the edges, or can pinch the labia or the skin of the scrotum. Choosing a saddle without a cutout helps reduce the pressure and pinching.

 A scoop, a depression or a channel in the middle of the saddle can be an intermediate design that works for some.

Rule #4.5: T or Pear shape?

This is only a “half rule” because there is no real guidance on it. The shape we’re talking about is the silhouette of the saddle when viewed from above.

Figure 9 A “T” shaped saddle (left) and “pear” shaped saddle (right)

A “T” shaped saddle has the usual narrow front, the usual wider back, and the transition between is also narrow.

A “pear” shaped saddle has a wider transition between the front and back. A pear is more triangle shaped.

Athletes who move forward and back a lot on the saddle sometimes prefer a more pear-shaped saddle. On the other hand, athletes who ride a wider saddle often prefer a more T-shaped saddle. Some riders find that a T shaped saddle can reduce chafing on the inner thighs. But there are no hard and fast rules for saddle shape yet.

Do the four and a half rules work?

Athletes who have never suffered saddle discomfort may not understand the need for this in depth saddle analysis. Even some riders with saddle issues might be blind to the beneficial effects of choosing a saddle according to the four and a half rules. They might have even tried and rejected good saddles, often because they didn’t feel right. But remember: if you only consider saddles that feel the same, you’ll keep getting the same. A saddle that makes a real difference usually feels really different. Once you know the four and a half rules and why they work, you can understand that the different feel means the saddle is working. Feel the difference!

Plenty of riders have confirmed that, for them, these rules can help improve saddle comfort, and thus training and racing performance.

What about tri/TT?

Once the torso and pelvis rotate forward in the typical triathlon or time trial position, the four and a half rules for road saddles go out the window.  With a forward rotated pelvis, the sit bones are typically up, off the saddle surface, and the weight is borne in various degrees by the pubic bone, inferior pubic rami and the surrounding tissues. The choice is now where do you want that weight to apply pressure? There are several strategies:

1. Pick a side.
2. Pick the middle.
3. Pick both sides.

None of these is proven completely healthy; in all the regions listed there are important blood vessels and nerves that shouldn’t be compressed for long. Nevertheless, the tri position requires this choice to be made. Different athletes make different choices, and saddle choice for the aero position is perhaps one of the least well understood in all of saddlery. We are not saying any one of these is necessarily the best choice for everyone.

Let’s look more in depth at the three choices, one at a time:

Pick a Side

Figure 10 Pelvis shown with red dot representing a normal road saddle nose on one side.

Picking a side works with normal road saddles. The athlete sits on the nose of the saddle, with the body offset to either the left or right side. The nose of the saddle bears on one inferior pubic ramus or the other. Most roadies do this unconsciously when “on the rivet”. They might not even know it.  Some fitters even suggest pointing the saddle to one side. A narrow, rounded saddle nose helps. The pressure can be quite high, since the weight is your body weight and the surface area is quite small.

Pick the middle

Figure 11 Pelvis shown with red oval representing a heavily padded saddle nose.

Picking the middle works best with heavily padded, wide triathlon saddle noses. The athlete sits on the nose of the saddle, centered on the soft tissue directly under the pubic bone. The pressure can be lower than picking one side, because although the weight is still your body weight, the surface area can be bigger; the trade off is that you’re sitting on the tissue that’s least able to take the pressure comfortably. For men, sitting on the middle can be somewhat tolerable, but isn’t healthy long term, as penile blood flow is stopped and nerves are compressed. For women this is rarely a comfortable position, as labia and clitoris are compressed and can be chafed.

By the way, very light, very powerful athletes in reasonably short events (say, less than 1 hour) can sometimes tolerate this okay by changing to a harder gear and pushing harder on the pedals, which takes some weight off the saddle.

Pick Both Sides

Figure 12 Pelvis with two red circles representing twin saddle noses.

Picking both sides is the ISM Adamo approach. The athlete sits on the two noses of the saddle, with the left and right inferior pubic rami resting on the left and right saddle noses, respectively. This works best when the athlete’s only contact is truly on the tip of the saddle, with most soft tissue off the front of the saddle. Pressure is on only the first few centimeters of the saddle’s noses, with virtually no other saddle contact. (This means for any constant body position, an ISM Adamo saddle should be installed 5 to 7 centimeters farther back.) For many riders, picking both sides may be the best of all possible worlds for the aero position.

Cervélo pros had been using or experimenting with ISM Adamo saddles, so when we chose a saddle for our tri/TT bikes Adamo was already near the top of the list. Since delivering Cervélos with ISM Adamo saddles, response from athletes and customers has been generally positive. At Kona 2012, ISM Adamo saddles were near the top of the list.

Nevertheless, saddle choice, as with all the contact points, is personal and individual. There is no single best solution for everybody.

What has been your experience with saddles?