Got my first car a week ago, already have a roof rack and slightly paranoid about bikes on the roof: must always remember that the bikes are there and not try to drive through low-level barriers..
Just thought I could put a blind-spot round mirror (like this one: http://www.tundrasolutions.com/forums/attachments/tundra/47352d1262293797-blind-spot-mirrors-mirror1.jpg ) to look upwards, pointing on the bikes, so I always can keep an eye on the bikes.
Has anybody done this? Can these kind of mirrors be adjusted upwards?

