I recently repaired my son's, now abandoned by him, Tesco special mountain bike which caused my wife to go out and by a Raleigh Caprice. So we pedal along the canal towpath near our home having great fun. However my wife's saddle seems incurable of the fault of tilting backwards/nose up after a short period of cycling. I've tightened it to the point that I broke a 17mm 1/4" socket. Any ideas, the bike still hasn't had it's first service.