1. Ensure that the wheel is fully back against the adjusters - You may need to pull the wheel to do this. 2. Tighten the Axle nut until it is just better than had tight (approx hand tight + 1/8th turn). 3. check wheel alignment (count the marks left and right) and adjust nuts as follows (loosen chain side / tighten non-chain side) until the alignment marks are now the same. 4. Physically check that the wheel is straight with respect to the frame - If so, all is well. If not you have a problem (see advice at the end of this list). 5. with the bike verical, and someone sat on it (about your weight), adjust the nuts 1/4 turn at a time until chain tension is correct (about 1/2 to 3/4 inch vertical movement in the middle). Make sure you adjust the nuts the same way (i.e. tightening by pulling the wheel rearwards). Fine tune adjustment as necessary. 6. Put bike on centre stand and with the rear wheel off the ground, turn wheel and ensure there are no tigh spots on the chain (if so, minor adjust (loosen) until OK). If this cannot be achieved, you need a new chain & sproket set! If wheel not aligned (4), then either the adjusters are fitted incorrectly, are not a matched pair, the rear frame is twisted, the wheel is buckled. Seek professional advice if you cannot spot the problem. All the best,