We've had some extensive threads on this. Campy NR cranks had a transition from crankarm to spider that turned out to be a stress riser. They were also very hard alloy, which made for very long lasting rings, but also meant the alloy was more brittle and cracked more readily. Stronglight cranks, by comparison, were softer, so rings wore out more quickly, but they rarely cracked like Campy. Almost all used Campy cranks have small, sometime almost indiscernible, cracks at the transition from spider to crankarm. Occasionally these propagate and the crank fails. They can also crack and fail at the pedal hole, usually where scratches from curbs, etc. had created stress risers. I don't think this is a simple function of age, its more likely a function of the number and magnitude of stress cycles, which would relate roughly to mileage and maybe the weight and riding style of the rider. But scratches and scrapes probably accelearte failure also.
The bottom line is, inspect Campy cranks regularly, and if there is a serious crack, retire them. I did this on a 1968 Allegro Special, where I found a rather nasty crack in the NR left arm at the pedal hole before it failed on the road.
Regards,
Jerry Moos
Houston, TX
Robert Kaufmann <kaufmann@crsa.bu.edu> wrote: All:
I have checked the archives, but could not find a good answer to the following issue.
Yesterday, I snapped my second NR Campy crank arm in three years. This time, the pedal eye "ripped" on a downstroke. (I fell over, but nothing more than road rash--the frame is unscathed). The first time, the arm cracked across the arm about a inch below the eye towards the axle. The cranks were installed at my LBS, and they are very good. So, I wouldn't fault them. I ride 3000-4000 miles per year. Once or twice a week, I ride hard (20-22mph) for 1-2 hour "time trials" but I am no monster. I weigh about 150 lbs. and am about 6 feet one inch tall. Clearly, I am no sprinter. I do climb well and like to get out of the saddle.
Both cranks were from the early 1980's. Are cranks of this vintage too old to be ridden on a daily basis? I really like the "look" of the cranks and would like to keep riding them. After the most recent fall, I am a bit hesitant to go to ebay and look for "lightly used" cranks. Is it best to pay my money and take my chances or is it time to "modernize" the cranks for my everyday ride.
All suggestions welcome.
Robert Kaufmann
Newton, Massachusetts