Originally Posted by agraham
if you're going the SPD route, make sure to note Shimano has two models: fixed or floating (I *think* that's what they're called). The floaters allow for a small amount of lateral pivot, and will not only disengage with a regular sideways twist, but also if you pull up on the pedal really hard. The fixed ones don't allow anything but a lateral twist.
If you're concerned with (hee hee) accidental release, go for the fixed (or non-floating, whatever they're called) cleats.
AG
The pedals I use MO520 come with SH-51 cleats which are known as 'single release' meaning they only release with a twist (rotation about the vertical axis of the leg) of the ankle. They have some (4deg) float.
The SH-55 cleat is 'multi-release' allowing a horizontal axis twist of the ankle in addition to the vertical - they also have 4deg float. These are known to release too easily. I don't have these.
I understand for the net there are SH-50 cleats which have no float. These are perhaps the ones I need, however I can find no source for them.
Al