My right drivers floorboard leans to the outside on my 2006 Electra Glide. I have tightened the two bolts but it continues to loosen and lean to the outside making me feel that my foot will fall off the running board.

I have tightened the bolts down as far as possible without breaking the bolts and yet this still happens.
Any suggestions what the cause may be and how I should repair this?

 

look underneath, the floorboard is made to pivot up if the bike leans far.

and you want them to be loose enough to do that ( rather than dig in and take weight off the tires).

push the floorboard up and see if there is room on top of the support arm for a small rubber stick on bumper- that may do it for you.
and check that the support arms are tight too

mike

 

Vibration. Remove the bolts, clean threads and put locktite on the threads and tighten back up. Should do the trick.

 

The bolts & nuts don't cost that much. Get some new ones.

 

+1 and get stainless steel.