While it seems couterintuitive, easing the sharp features that create the riser wherein crack intiation begins. If there is too little metal to start relative to the stresses applied, a piece is going to fail anyway. In many instances, there is enough material for strength but the forces are distributed to a thin weak area. In the case of the Campagnolo spider/arm junction, there is enough material. I've relieved a handful of them that most definitely were cracking down to (and a bit beyond) visible crack and never had one fail subsequently. But then I don't weigh 250 pounds and I'm not a sprinter. However, I do climb hills with gearing that is a too tall (you'll have that with 41 or 42t rings) so it bears consideration because I don't really want to fall face first into the pavement.
This should be done as a prophlactic measure even on cranks that don't show any outward sign of cracking. Can't say that I've inspected (or relieved) all of the ones that I have - probably around 15 or so... Only takes about 2 to 3 minutes with a chain saw file followed by a bit of fine sandpaper to take out the scratches from the file that, in turn, could be stress risers on a smaller scale. Not very noticeable and, if you see one that has been so treated, might indicate a conscientous previous rider that probably cared for his equipment.
Charlie "no warranties exended or implied" Young Honey Brook, PA
> Hi all, I've read about the stress cracks that plague
> these cranksets and I think I read somewhere about a
> possible help. It said that you take a round file to
> the "sharp" edges between the crankarm and the "star"
> and round it over a bit. Does anyone know if this
> works? It almost seems counter-intuitive to eliminate
> metal from an area that suffers stress cracks.