Rubber Snubber

[kritter]

I need to have made a rubber bumper for a shock absorber in a race application and I have very limited knowledge of what type of rubber I need to call out. The only loads this bumper will see is compressive loads. It is going to be .375 tall, 2.875 OD with a 1.25 hole in the center. I would like the bumper to compress 50% at 500lbs force.

I see companies using urethane but I am worried about cracking or the bumper squirting out the sides since the sides will not be supported.

Any feedback is recommended...type and durometer specifically!