According to simple law of physics, the static friction is only a small portion of gravity of an object, the factor is called static frictional coefficient. Unless you have some tank tracks or sticky surfaces (spider man), you will not have a static friction that exceeds gravity. So you will not have a deceleration greater than g.
Somebody has something to say about this coefficient for tire on dry road:
http://hyperphysics.phy-astr.gsu.edu/hbase/mechanics/frictire.html
As for the braking thing, I think you should ride with an accelerometer and record the entire process of a number of hard breaks, soft breaks and what not so you have data to look at. Without data, I could argue 0.5g is trigger and needs to be at 0.5g+ for 0.1 second and you say different and neither has proof this is what actually happens.