chain comes off rear derailleur

Flip the bike over on a table and shift it while pedaling by hand and then you can see what
it is doing, you need to set the limits for the derialleur. Did you get the bike at a shop or
dept store?

They should take care of the adjustments in either case. But it is not hard to do your
self and you need to learn about the bike as well.

What kind of shifter? Brand? The model you bought, they have dozens of models?

The right side shifter should control your rear derailleur. With the rear wheel off the ground while turning the crank forward move the shift lever to 1. If the chain does not move all the way to the largest sprocket on the rear wheel your cable is to loose. To correct this you now have to move your shift lever to the highest number while pedaling. The chain should move over to the smallest sprocket in the rear you are now in the proper position to adjust your cable tension. Screw the barrel adjuster half way in loosen the screw that attaches the cable to your derailleur and pull all the cable slack to make the cable tight. While holding the cable in this position retighten the clamp screw. Start turning your crank forward if the chain trys to move to the next largest sproket without moving the shift lever adjust the barrel adjuster a half turn in turn the crank again if the chain stays put on the smallest sprocket you are ready to test your adjustment. Move the shift lever over one position at a time the chain should move one sprocket to one number. If all is correct it will shift through all the gears properly. This is a lot easier than it sounds. Good luck and if all else fails bring it to your LBS for adjusting. Also you can find derailleur adjusting tutorials on line that you can watch.

Quoted post said:

Originally Posted by thisuserisme [IMG]/img/forum/go_quote.gif[/IMG]

i'm a new cycler and bought a low end 18 speed Pacific bike. when i pedal the chain comes of the rear derailleur. it will go off and come back on. i don't have to stop riding but it's not good. also shifting stinks. i shift the left and right and only seem to get about 3 gears. right side is numbered up to 6 and the left side has lots of lines that i can click into. the user manual covers every bike made by pacific so it's not very helpful. how can i fix the derailleur issue?

Have a read of this:

techdocs.shimano.comblevel.jsp;jsessionid=8v3xMl9Qmn9QwdLcJwGtWK2T9s2qJ9QDJRZGTG075JG9LJyvTzRQ! 208679273Open ↗

It has pretty much everything you need to know about getting indexed gears to work. Just work through it step by step. The rear gear adjustments hold true for both road and mountain bikes so you'll be set whatever type of bike you have...

... unless you just mystically happen to have Campagnolo Syncro indexed gear levers from the mid to late 80's - in which case I'd just off a tall building.

I don't see how a chain can come off a rear derailleur, unless the chain has been routed around the jockey pulleys incorrectly. For adjustments, see
http://sheldonbrown.com/derailer-adjustment.html

Take a look at the Park Tool website; link below takes you straight to the section on rear derailleurs. Good, photo-illustrated step-by-step instructions.
http://www.parktool.com/repair/readhowto.asp?id=64

thanks. i will check out the online video and tutorial. i'll have to get back about the model etc.