This article is from the Mountain Biking FAQ, by Vincent Cheng.
-Clipless pedal riders are connected to their bikes by cleat and
mechanical "hooks". There are many pedals out there on the market, each
with their own designs. In this FAQ, I will NOT recommend any specific
model because the technology changes too fast for me, and also it has a
lot to do with personal preference.
-Advantages: Very solid connection from the bike to the rider. Once the
rider is experienced, it will be easy for him/her to unclip. It's cool.
It helps many to bunny hop (read:hop/jumps).
-Disadvantages: Cost. Fear of being clipped in when you need to remove
your feet. Must be used with cycling shoes.
-Float is the amount of side to side movement the pedals allow before
releasing the cleats.
-To engage, simply step into it and one of the hook/bars/clips will snap
back. You should hear a "click" when you are in place (except ONZA).
-To disengage, twist the foot inward or outward to release, again, you
should hear a click (except ONZA).
-When first learning, it is best to set the pedal to the lowest release
tension. This way, beginners can clip in/out easier.
-Practice on a grass field so that when you fall, you are not going to
get hurt. Ride around on the grass and try to engage and disengage each
foot. Leave the non-practicing foot unclipped in case you fall.
-Do not ride on the streets/trails until you have mastered these skills.
-Turn up the tension as your skills increase.
-Try lubing all the contact points between the pedal and the cleat and
also all moving parts to improve the smoothness of engagement and
disengagement.
 
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