I found a good deal on a set of Harley brand detachable saddlebags on ebay.The description says they won't fit with rear axle covers.Anyone know why.It doesn't look like there is a bracket that goes to the axle.I want to keep my covers on.

 

It might be how close they sit to the rear axle.

 

That would be my guess too. But on the bright side.
If they are that close to the axle ends, once installed your probably not going to be able to see if the covers are on there or not.