My brakes suck, as some may recall from previous posts, but when I brake hard enough down this one 15 grade incline on my commute my fork really vibrates. This vibration causes the braking to seem weird (that is how I first noticed it). What will happen is that my brakes will operate normally and then every half second or so the front of the bike will like... I can't explain... Not jump but like have a small but sharp "knock" and the brakes will resume normal operation.
At first I thought maybe my front rims were messed up (like something was knocking against the pads or some irregularity or something), but now I can tell it is the fork.
This leads me to my question - how much vibration/flex is okay for an aluminum front fork? Mine will flex maybe 3/4 of a centimeter and vibrate under the most strenuous braking.
 - the vibration's effects on the braking and weird knocks and stuff has been happening since I got the bike, and I don't think that the level of knocking actually could interfere with braking performance a lot so this isn't a life/death situation ^.^