whilst cycle helmets are not mandatory, especially in the fats moving traffic of rio, they do give cyclists an extra level of protection - and a real must have. 

due to the heat of the local weather, carrying water is advised, to avoid dehydration.

even on cloudy days, the heat can result in quick exhaustion, thus riders should always bring along a bottle of water, and sunscreen to prevent sunburns.  

as rio de janeiro is such a busy metropolis, picking the right time to go for a cycle can also help - weekends and holidays are generally considered the best time to cycle in rio, as some of the avenues are closed, for leisure activities.

rio de janeiro is a truly rewarding and diverse place to go bicycling - and is very welcoming to those who opt to cycle over less environmentally-friendly forms of transport but, and taking the necessary precautions will insure and even better experience.