How would the bike handle going from a 100mm fork to a 140mm on my GT Avalanche Sport 2016, would it be safe? Suntour XCT HLO 100mm to Rockshox Revelation RL 140mm
Generally you don't want to go more than 20 mm from the intended fork travel for a frame. More than that starts to change the geometry of the bike too much and can cause excess stress on the frame, sometimes leading to cracking/breaking. I'd suggest going with a 120 travel fork, and if you still want more travel, consider a bike upgrade.