Originally Posted by TacomaSailor

iPhone 3GS - February - July 2011 (1800 miles? 1/3 on my mountain bike) I kept the phone in an Otterbox. The phone started having serious problems in June. It would start/stop/make phone calls/delete apps...etc with no input from me. Even while sitting quietly on the desk in front of me.

Apple store took it apart and found contamination and corrosion around the little round button at the bottom front. They replaced the phone under warranty.

The technician who did the work was a semi-serious cyclist. He and I had a long talk about iPhones and bicycles. His urgent recommendation based on a lot of warranty returns like mine was to not use an Otterbox or similar waterproof container.

He said they did protect the phone from getting soaked or damaged from impact and were excellent for that purpose.

The problem is that the waterproofing allows/forces any moisture that gets in the phone to remain in the phone. As the phone inside the Otterbox goes thru heating/cooling cycles it allows the moisture to evaporate and then condense. That leads to the corrosion he found.

STRONG recommendation from him - use the phone with no protective case most of the time. When riding - put the phone in a ziplock bag for the duration of the ride. Then remove it from the bag when the ride is over.

He also said it was OK to use the Otterbox when riding but to get the phone out of the box after the ride and let it air and dry. That is too much work for me!

Additionally, I get a much better GPS signal with the phone not in the Otterbox. That is especially important in the Pacific NW mountains where the GPS satellites are low in the sky. The phone would frequently lose the GPS signal when in the Otterbox but regain when outside.

August - December (2500+ miles - 1000 on a mountain bike) following his instructions and no phone problems. I carry the iPhone all the time and use MotionX-GPS on every ride. I use cheap/disposable 'zip lock' type of bags.

I carry the phone in my jersey pocket or the outside mesh pocket on the small backpack or fanny pack. I've ridden in rain, snow, sleet, wet roads and have had no problems with the phone getting wet.

Just my personal experience.