Sit bone width is the measurement that should decide your saddle — more than brand, more than padding, more than how a saddle looks. Your two sit bones are meant to carry your weight; a saddle only works if it is wide enough to support them on its structure instead of on soft tissue. You work directly with me, Lloyd Thomas.
What sit bone width is
At the base of your pelvis are two bony points, the ischial tuberosities, that press down when you sit. The distance between them is your sit bone width, and it varies a lot between riders. A saddle’s supportive zone has to sit under those two points. When it does, load goes through bone; when it does not, load goes through the soft tissue that was never meant to carry it — and that is where numbness and pain start.
How it is measured
The principle is simple: capture where the two sit bones press down and read the centre-to-centre distance.
- an impression on a memory pad, measuring gel or equivalent tool
- read the two clear pressure points, measured centre to centre
- in a fit, combined with your actual on-bike posture, not just an upright sit
That last point matters. As you rotate forward into a riding position, the contact area shifts, so the number off an upright pad is a starting point, not the whole answer.
Why width beats softness
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Too narrow: your sit bones drop off the supportive shell onto soft tissue
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Too wide: the edges chafe the inner thigh through the pedal stroke
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Too soft: padding compresses and pushes up into soft tissue instead of supporting bone
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Correct width and shape: weight goes through the sit bones, where it belongs
Where this fits your decision
If a saddle hurts, sit bone width is one of the first things to check — the wrong width cannot be fixed with padding or angle alone. A fit measures it directly and reads it against how you sit on your bike, so the saddle choice is based on support, not guesswork.