Core each pear and cut lengthwise into 8 wedges. Toss with 1 tablespoon of the lime juice to prevent browning.
In small jar with tight-fitting lid, combine remaining lime juice, lime peel, honey, oil and pepper; shake well.
Arrange spinach and radicchio on individual salad plates. Fan 4 pear wedges on each plate. Sprinkle with walnuts and cheese. Spoon dressing over salads.