Road Fan

Frank, this is very surprising! Does your 150 mm come from a measurement, like they do at Specialized stores? Have you tried any Specialized saddles? Which one of those works well? Mahy of their models come in 155 mm width. In those I like the 143mm. I vaguely recall my Specialized measurement being about 115 mm. That doesn't mean I don't have a fat butt, it just looks at my skeletal dimensions. It's just about the bones.

The full-width across a S-A saddle (there's only one width, actually) at the widest point is 170 mm. For a Brooks B17 it's 172 mm on one I have (I'm not sure if they're all the same, either the Brooks or the Selle Anatomica!), and most saddles seem to be intended for the front-rear placement of your sit bones to be at this widest point. The S-A also has a little dimple in the middle of each half of the widest point. You can feel them with your fingers, but they're hard to see. Those are about 75 mm apart. For both saddles that maximum width is fixed (it can't "shrink") by the steel cantle plates, to which the leather is riveted 6 times. So the cantle plate determines the width of the saddle's supple section that supports your weight.

The width of that supple portion of the saddle leather is about 2 cm less on each side, so for both the SA and the B17 that free width is about 130 mm, or about 5.1 inches. So for anyone with sitbone width 5.1 inches or less, you should get a supple span of leather to hold up your butt when it is as far back as it should be. Many riders need to tilt the saddle nose up somewhat to help them stay in that position.

For any saddle, you can check where your sit-bone pressure is focused relative to the saddle. It's really easy, just sit on your finger while you pedal. If your finger is under the part of the sit-bone that has the most pressure, and is close to the widest part of the saddle, that is just about what I think is correct.

One way an SA can fit you too narrow is if you are trying to sit near the bottom of the hammock. If you look at an SA from the side, it will usually have sort of a hammock shape, even when it is tensioned up correctly. This part of the saddle is softer, but it puts the pressure of your weight on parts of you that are not intended to support your weight. God did not intend your "boys" to be sat on. It seems He did intend your butt bones to have that job. Really, the same issue exists with any Brooks, and for an Imperial with that slot, it's a LOT like an SA.

If the tension of an SA top is too slack, your weight can sag it down until you are actually resting on the top of the seatpost, in an extreme place. To make this sitbone balancing act work, you should check before each ride (this is just my approach, what I do) that the narrowest part of the slot is pretty close to 6 mm gap. I take my multitool and fold out the 6 mm Allen (hex) tool and pull it through the slot, across the flats. If it just drags a tiny bit, that is about right. Adjust that gap by tightening the nose crew, which takes the 6 mm Allen which should already be in your hand. This procedure comes from Selle AnAtomica, it's on their website.

If you're sliding forward as you pedal, your contact points might not be placed to maximize your best pedaling. I've sometimes found I am reaching forward too far or my body wants to slide forward, or I am pushing back with my arms. One possible solution is to raise the nose to make it harder to actually move forward - this helps with the butt pressure but not with the back, hands, or arms Another is to slide the saddle forward to let your butt be on the wide part AND let your body be forward, on the theory that generally speaking your body goes where it needs to. Both remedies can result in butt pressure and abrasion not being such a problem.