it's GT avalanche 2 disc, rear derailleur is Shimano Alivio
chain is almost on every bump or my lame jump hits the frame, even if it's 2-inch jump
Is there anything i can do about it? it's really annoying.. my buddy's Huffy is dead-silent when he jumps
You might want to try a Lizard Skin chain stay protector. They're designed to protect against chain slap and cost around $7. Or you can zip-tie an old inner tube to the chain stay. Same results as the Lizard Skin.
Also, try to use the biggest chain ring and preferable a larger sproket in the rear. This arrangement will increase tension on the derailler, and keep the chain further away from the stay.
You're correct. Never cross your chain (big chain ring with big sproket OR small chain ring with small sprocket). I tried to dance around it by saying "bigger" sprocket.
Oh, alright. I was just thinking by bigger you meant the biggest. My advice would be stick with the middle chainring up front at all times. Puts the lease pressure on the chain from side to side. With the exception of flying down trails where you need the biggest chainring or climbing up steep hills where you would need the smallest.
zip ties and an old bike tube work great and you dont need to spend any money
the best way to do it is to wrap it aroung the chain stay as if you were wrapping handle bar tape on the handle bar of a road bike (if you know what i mean) cutting the tube and just putting around the chain stay with zip ties is no good
Any bike with a properly-sized chain is pretty much guaranteed to have chainslap. You can try increasing the B-tension a bit on the derailleur, but make sure you don't go overboard. Even then it probably won't completely eliminate the slap.