Take wheel off you will see them. Removal and refit can be anything from a piece of **** to a bloody nightmare. They should twist out side to side to loosen them. If they are stuck try fitting a pipe clip around them and gripping that gently with some grips to get them moving. Again twisting motion side to side gently does it. When replacing grease up with some silicone grease, push them in until they touch reluctor ring. Wheel revolving will set air gap.
