Originally Posted by
TejanoTrackie
I have a set of Pista cranks that came with my 1976 Schwinn Paramount P14 track bike, which are the older 151mm bcd style. Were the Strada failures on 144mm bcd cranks, and where exactly did the failures occur?
The most common failure seems to be at the junction of the spider with the arm:
The sharp edge of the machined junction creates a stress riser that leads to crack formation as above. Using a round file to round off this edge distributes the stress better, lowering the chance of crack formation.
Other failure spots include the pedal eye:
And the square broached hole for the spindle.
The 151mm BCD arms aren't that different from the 144mm BCD arms.