my chain falls of front sprocket

[mattpace]

Hello, I am new. I am lazy too, so I am just going to copy a post from another forum (but also by me). Any help is appreciated.

Hello, I have been riding my new giant and I have had the chain slip off the front sprocket several times. I will be JRA down a hill at a fairly good speed and I will slightly backpedal. The whole chain will slacken, then fall off the front sprocket. It only happens in 7th and 8th gears (my 2 highest), and I can recreate it by standing the bike still and pedalling the pedals backwards as fast as I can (with my hands). The rear shifting arm (dunno what its called, sorry, new to this) will suck in towards the middle of the bike, causing the top chain to slacken and drop down, and then it falls off the sprocket. We lubed everything in the rear, the cassette, the shifter, the entire chain, and it helped, but only slightly. The bike is brand new, and the first 2 times it happened it was on the road, so it shouldnt be dust or dirt collected in there. Any ideas are greatly appreciated.
Thanks in Advance,
Matt

[svfreerider87]

I just noticed in the picture that you do have a chain guide? if not then i reccomend you purchase one.

[crashnscar]

If it's brand new, bring it to the shop where you bought it and tell them the problem and they should fix it

[ds1sucks2ride]

your rollers are prolly not aligned so when you pedal back it derailes it cleanely. MY mrp was doing that for a bit, then i changed the alignment

[mattpace]

I am assuming you are talking about the two little rollers next to the large sprocket. Those travel back and forth, should I lock them up so that they just spin? I cant take it back to the shop, it was bought in Taiwan. I have asked 2 seperate repair shops, and they both think it has to do with the rear hub. I will try the chian guide and let you guys know how it goes.

Thanks a lot

[crashnscar]

I just saw the pic of it (the Giant Warp DJ)......
The Truvativ rollers should be far enough down that the plastic parts that hang over the side are covering the whole chain. The inside part should not be rubbing against the chain, but pretty close (maybe 2 mm in between)

Hope this helps

[mattpace]

good to know, right now they are rubbing them pretty good. Ill adjust that.

[quietriot447]

with your chain issue i think (not 100% sure so dont blame me if i am wrong) that it is your free wheel that is messed up. mine does the same thing but not nearly as bad,it only switches gears, so i can live with it. i dont know if that can be fixed but you might need a new rear hub or depending on the quaility of your rear rim a new wheel might be better. but i dont know of any quick fixes cause u said u were in debt

-tom