Hi

Need help on how hard and what kind of material would be best for a shaft that I am using.

Shaft is used for an assy used in racing called a coil over elimantor. The object of this part is to carry the spring for the car, it is alot like a coil over shock but there is nothing in the shock part. We started out with a w-1 shaft 5/8 in dia. and we bent it, 2nd we tried an s7 steel shaft and heat treated it to a rockwell of 50 to 57 which turned out to be to hard, and broke. This shaft and assy will carry around a 200 pound spring and will compress 3 to 4 inchs. I was thinking about using a sheffield # 20 shaft that is about 28 to 32 rockwell,  but need any help that i can get.

Thanks Jay