When I have repaired steering wheel cracks in the past I've used Tiger Hair. It's chopped fiberglass blended in a resin and you add a few drops of hardener to the amount you need for the job. When repairing cracks in your wheel you first need to grind it out a little and taper it in to the bottom of the crack. the wider the taper the better. Then fill and sand after hardening. Apply more if needed till satisfied with smoothness and look. Any two stage epoxy with fiberglass strands will work. By tapering and feathering in your fiberglass filler it should never crack again. Paint with a two stage epoxy paint. To eliminate cracking; avoid direct sunlight and extreme heat. Cold temps have no adverse effects, unless you smack it with a hammer or such. Also avoid using your steering wheel to keep you from going thru the windshield when you slam on the brakes at stop lights, animals crossing the road, or pretty girls standing on the corner, etc. etc.