That's a good question, that we don't really have answers to.
One front and one rear caliper cracked. The front caliper started to make creaking noises during a track day and then progressively lost braking effect during the day. When we pulled it, we found a crack, on inspection, we also found a crack in a rear caliper.
The cobra is a light car, I don't think I am that hard on the brakes (others may disagree
).
So having already had a previous adventure
with these brakes, I chose to upgrade to AP's, and am very happy with the result.
Cameron