I know that, this is from an engineer. and if I were building a car it would be CM. but there is nothing wrong with a MS car.

Not to be a stickler, but when I was in engineering school 20+ years ago it was known as Chrome Moly, which is a steel with significant alloying elements of chromium and molybdenum. One misconception is that a moly car will be stiffer (all other things equal), but 4130 has the same modulus of elasticity (basically spring rate) as 1020, it just has a higher yield and ultimate strength. In other words, if you have two equally sized bars (of 4130 & 1020 steel) and stuck 500 lbs on each, they would deflect the same amount (as long as you are below the yield stress of the 1020). However, there is a load level where the 1020 will be permanently deformed but the 4130 can still spring b