Realising that there are "Certain" correct ways of positioning the saddle on height and fore and aft---
I had a similar problem about a month ago. Been riding that bike and that saddle for a couple of years and no problems but on one ride- the sit bones kept riding forward and it started to hurt. I adjusted the angle of the saddle and then pushed the saddle 1/2" further forward. Cured the problem but why the saddle suddenly went "off"- I still haven't found out.
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How long was I in the army? Five foot seven.
Spike Milligan