Bicycles are permitted on the 'L' (CTA trains) every weekday except from 7:00 a.m. to 9:00 a.m. and 4:00 p.m. to 6:00 p.m. (except on July 3 and 4, and in cases of extreme crowding).
On Saturdays, Sundays and holidays (excluding July 3 and 4), bicycles are allowed on trains all day. If you board the train with your bicycle before the hours listed above and your trip extends into those hours, the CTA allows you to finish your trip.
Always be mindful of other passengers.