Cause of broken cleat?
 

I installed some used cleats that had around 100 miles on my new Giro Apeckx shoes.
I went out on a test ride around 6 miles. On the way back home I started sprinting, and I felt my foot pull up from the pedal. I pulled over and noticed my right cleat was not on my shoe anymore. The cleat was stuck on my pedal and the bolts were still attached to my shoes.

Was this a cleat failure? Bad/cheap cleat?

I did install the cleats with the shorter cleat bolts that were provided with the shoes due to the low-stack height.

M2C:
1. Not original Look cleat.
2. Taking off and screwing on (maybe too tight) weakened it at the spot where it broke. Did you use washer?

Yeah I did use the washers.

Looks like you used round washers, rather than the normal rectangular type, which spread the load better.

http://i81.photobucket.com/albums/j2...ps3cfbe290.jpg

Sprinting? Clearly an over-watt condition; just too many watts for the cleat to handle. Either get off the juice, or get DTC (droping teh hamer) certified cleats, which are basically kryptonite reinforced diamond nanofiber (with a cosmetic 3k carbon weave). ;)

In all seriousness, you can see the washer indents, and it looks like they were too small diameter and overtorqued, which as mentioned above, was almost certainly the cause of the failure.

That and the fact that they are less expensive aftermarket cleats using inferior plastic (I'm guessing a Chinese vendor).

Cheap is as cheap does.

Light, strong, cheap....pick two. :)

Used aftermarket cleats. The double whammy.

Glad it only cost you some new cleats and not a pound of flesh...

Keep it under 400w, bro. Your equipment can't handle that kind of power.

Yeah. Coming out of a pedal while standing, particularly at high effort, can cause a nasty crash. Judging from pic, washers look missing or wrong. Probably not worth going cheap on cleats. I get genuine Look products from Ribble for cheap...in which case I guess cheap is OK.

Round washers are the wrong answer. the rectangular ones fill those slots, reinforcing the plastic. Looks like the front slot broke, and then the cleat slid off of the other two.