Bicycle Mechanics - rear derailleur help!

My rear derailleur won't push my chain into the 3 largest cogs. I can't push the lever on my rapid fire shifters all the way down, it feels like a shifter normally does when ur on ur largest or smallest clog and try to shift up/down. Does anyone know how to fix this?>


Thank you

There are two screws which adjust the stops. But if it worked before, it may be bent. Check out this page.
http://www.sheldonbrown.com/derailer-adjustment.html

Something is screwie. Usually, if there is trouble, it is going from the large sprockets to the smaller ones because the derailure spring doesn't have enough oomph to pull the chain toward the dropouts.

In the case of going to the larger sprockets, you can usually provide enough power with your hands on the shifter to pull the chain over.

Clean and lubricate the derailure and see if that helps.

Check your cable tension to make sure the cable isn't slack. Use the shifter to get the chain onto the smallest sprocket and then take up the slack. Don't pull tight, just take up any slack.

If that doesn't work, take your shifter apart and see if you can find anything.

thumb force definatly isn't doing it, the chain is lubed, and the cables are tight.

Well, then, maybe Dirtgrinder is on to something. Is it possible that you might have bent the derailure?

If you did, I don't think it is worth trying to straighten them. It rarely works.

sorry this is a little late but why dont u just loosen the low limiter screw on the derailleur. this will allow it to shift to those gears.. if you have to loosen it tho it means u banged it or something.. loosening it and adjusting the cable once loosened should fix your problem