Originally Posted by
Wogster
The benefit of a steel fork is simple, in a severe crash where steel is forced beyond it's deformation point it will deform (read bend). Carbon fibre when forced beyond it's deformation point, will splinter. Of course the difference between a fork that bends and one that shatters, could be the difference between calling a driver a dumb*ss, and paying for a good chunk of your dentist's new Porsche....
My own exerience with a carbon fork on a steel frame is that the frame will crumple before the carbon splinters. I once had my bike completely lock up the front wheel when a broken fender stay was caught by the front tire at around 25 kmh. The fork survived completely intact, but the steel frame was toast (so was my helmet, btw!). This was a steel frame, so there'd be stress risers at the end of the head lug below the downtube, or at the end of the front butted section of the downtube. Anyway, downtubes are not designed to absorb the force of a direct hit from the front, so would be more likely to give than a fork, especially one made of carbon fiber, which would usually be much stronger than one made of steel (for a given weight).
Also, a carbon fork designed for disc brake use would be much heavier than a normal rim-brake fork. I've seen weights closer to 500-650 grams for disc brake forks, vs 300-350 for a light rim brake fork. The disc brake fork is one place where I would NOT file off those stupid lawyer tabs!
Luis