Funny story: Had a moderately bad crash on my steel single speed commuter. Trued my wheel, buffed out the scratches, healed up, and got back on the bike. Was noticing a weird unsteadiness, a shimmying feeling at mid-speeds, and noticed my feet kept contacting the wheel when I was turning. Rode it a while more and then took a look at my wife's bike from the same maker... and realized that I had hit the fork hard enough (and straight on) to reduce the rake by probably 1.5 inches! Instant conversion into twitchy crit bike at low cost!

Before:


After: