different shorts and saddle.
the first time i did a 100 mile ride, my shorts rubbed my head raw, raw like you would not believe. i could not not take it any more and had to stop at around 90.
new shorts, a good pair, and never had the problem again, or maybe it just toughened up
. anyway, pearl izumi's is one brand i used. dont go cheap, get the best even if it means less pairs. i did go to bibs too.