I’ll start with a very simple solution. Move your foot forward on the pedal. This, of course, only works if the strike is not too severe and if you’re not using toeclips or clipless pedals; in which case you don’t have the option of moving your foot forward on the pedal. Or, if you’re like me, there is a sweet spot in the foot/pedal connection and you’re not going to be comfortable moving your foot too far off of that position.
Of course the size and shape of the bag is a factor in heel strike. It’s the reason that we made the Elinor a wedge shape. Panniers like the Gilles Berthoud 799, in addition to being a beautiful bag, offer good clearance by virtue of their diminutive size. I don’t think much more needs to be said on the matter.
Another solution is moving the bag back away from the rider. There are two factors (maybe more, I can only think of two right now) that come into play here. First is the set back of your rack. The longer the rack or more setback it has, the farther you can move the panniers away from rider toward the aft of the bicycle. Many newer racks have a longer top surface area and allow you more pannier placement options. By contrast, the constructeur type racks come straight up vertically off the rear axle and have a small top surface area.
Hooks and Straps
The other factor is the placement of the hooks or straps. Hooks and straps that are placed closer together on the bag or are adjustable like Rixen and Kaul, will generally permit the rider more placement options. Our pannier hooks are not adjustable but are placed close enough together to both fit on the small surface area of a VO constructeur rack and allow the rider to move the bag quite far on a rack with a more substantial setback.