When patching any cast material whether it a concrete side
walk, asphalt driveway, porcelain cookie jar or a hard rubber
steering wheel, it's impossible to duplicate the original
continuity of the original material at time of manufacture.
The AD steering wheel was a combination of raw natural rubber,
ground up used rubber, a filler which could have been Portland
cement or clays and god only knows what other materials.
The best one could hope for when patching a crack would be to
find a modern material that would match the original material
in density and flexibility. That would probably be a urethane
of the correct durometer.
I can't say for sure, but I'd bet a dollar to a donut that the
steering wheel repair kits that are on the market are simply
epoxy which, although they will fill the crack, they cure
quite hard and do not come close to matching the original hard
rubber compound.
The epoxy repair kits, are most likely just inexpensive
xx-minute epoxy and will fill the gaps but in many cases,
in use will eventually start to separate from the original
material.
Urethane can be had in any density from soft as the baby's
butt to as hard as granite rock. Kit's are available from
suppliers such as Reynolds Advance Materials. They aren't
cheap though, but in my opinion they would be the best
match to the original hard rubber.
http://www.reynoldsam.com/Denny Graham
Sandwich, IL
