Streetpilot on my mountain bike

 

I was wondering if anyone else has tried using a car GPS for their mountain bikes. How did you mount it? How did you handle battery issues?

I have a Garmin Streetpilot c550 which I wanna mount on my handlebar (or maybe on the bike stem). I saw some cool RAM mounts but I wonder if those would be enough to minimize vibration.

Thanks for the help.