In a large mixing bowl combine chopped chipotle peppers, onions, beer, balsamic vinegar, apple cider vinegar, oil, maple syrup, and salt; whisk until completely incorporated.
Place pineapple rings in a ziploc bag and add ½-cup of the prepared marinade to the pineapples. Seal the bag and refrigerate for 4 hours.
Place chicken thighs in a large 1 gallon ziploc bag.
Remove ½-cup of the marinade to use for later. Keep refrigerated.
Add the remaining marinade to the chicken thighs; seal the bag and refrigerate for 4 hours.
Preheat the grill to 400˚F.
Remove chicken thighs from ziploc; discard the marinade. Let thighs sit at room temperature while preheating the grill.
Brush the grill grates with oil.
Transfer chicken thighs to the hot grill and place over direct heat; cook undisturbed for 5 minutes.
Flip the chicken over; brush with the reserved marinade and continue to cook for 5 more minutes, or until chicken is cooked through and internal temperature registers at 165˚F. Brush on more of the reserved marinade while the chicken is cooking.
Remove chicken from grill and set aside for 5 minutes before serving. Keep covered.
While the chicken is cooking or resting, grill the pineapples on both sides until grill marks appear; about 1 to 2 minutes per side.
Place chicken thighs on a plate and serve with the pineapple rings.