Joined: Jun 2014
Posts: 111
MPI has a trailer safety brochure
5/10/2017 at 7:04 PM
it says: Mirrors for your towing vehicle
When you’re pulling a trailer, you must have a clear
view to the rear of your trailer. To do this, you may
need to reposition your vehicle’s mirrors or add
extended mirrors.
When you’re not towing your trailer, remove any
mirrors you’ve added to your towing vehicle.