They are made from the same special alloy steel as coil springs, and are supposed to be tempered just like coil springs, which requires heating the whole thing until it is glowing red, and then quenching the whole thing in oil, which is what leaves it with a black finish, rather then shiny like the steel starts out. This hardens and tempers it, so that it resists bending permanently, and will spring back to it's original shape when bent. (within reason, at least)
Any extreme heating of any portion of spring steel, and then allowing it to cool gradually, instead of quenching it, will lose its temper, and if it is then bent, it will not entirely return to it's original shape.
That is why it is not a good idea to heat coil springs to lower a car, they will then continue to sag a little more each time they are collapsed, and lose their ability to hold up the car.
Mark Donahue, in his book, mentions having serious problems with handling on the second year Camaros they raced in the Trans-Am Series, the car would handle perfectly when they first took it on a skid pad, but would get progressively worse, the longer they circled the skid pad, and would handle great if they reversed directions for a few laps, then would get bad that way too. They finally figured out that an entire batch of the front sway bars for the new Camaros were not properly tempered, so they would eventually twist if you went one way long enough, and lose their effectiveness. They had to send them to a spring shop and get them re-tempered.
Chrome-moly steel is close to the same as the spring steel, and will take a temper the same way, if you can find a spring shop near you that is equipped to do it right. So it is not that hard to buy your own, and bend it to the right shape, and then get it tempered.
Hope this helps ya.
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Gerald Storvik
http://www.8shark.com
