Any question answered...

my super expensive, super comfortable assos bib shorts have worn so thin at the back that when i'm on my bike you can clearly see an inch of arse crack through what now looks like thin, ladies tights material.
it's not pleasant for anyone behind me but the shorts are my favorite and i can't afford to replace them -in every other respect they are still in perfect working order.

any ideas how to fix them?

This has happend to three pairs of Assoss bibs/knickers now all around the top end of my crack.

My plan is to get my mum to sew a patch of lycra on top of it (from a cheap pair of shorts I bought). I've had the cheap pair for a year now and haven't taken them to my mum for sewing yet so ask again in 2013 or something.