Front Derailleur - Is It Bent?

[bunman]

I recently bought a 2nd hand Specialized Hardrock Sport, unfortunately, the guy that owned it before seems to have made an arse of some of setting it up. One problem is the front derailleur, originally, it was about 1.5 - 2cm above the largest cog. Anyway, I've lowered it to about 1-2mm but I cant seem to get the derailleur to get the chain to go into 3rd. I'm about to give up but thought I would post a picture of something I'm not too sure about. The outside cage, at the very front is bent in slightly, I thought the outside edge should be flat. Hopefully the photo will show the bend. The derailleur is a Shimano Acera.

[nameused]

Mine doesn't seem to have that bend in it right there. By the look of your picture you might want to adjust the derailleur more to the right. It looks like the chain is rubbing on the right side of the derailleur.

[bunman]

Thats my problem, I can't seem to get the derailleur to go far enough across to clear the 3rd cog. I've tried everything, even following the video guide here step for step. Is it possible that my gear lever just isn't pulling the cable tight enough to get the derailleur to push away from the frame enough? Is there a setting or adjustment for setting how much the derailleur moves for each increment on the lever? At the moment 1st gear is fine, 2nd gear isn't too bad, but the chain can rub against the derailleur sometimes, depending what cog I'm in at the back. 3rd is just a no go. I've nearly got everything else on the bike sorted, but this is driving me mad :O(

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Looking at the photo, it looks a bit like the metal plate just below the plastic piece with the shimano sticker is bent in a little. If the cage is bent in a bit, that would be a pretty good reason for not being able to clear the 3rg cog, wouldn't it?

[nameused]

(11-08-2010, 07:37 PM)bunman Wrote:  Thats my problem, I can't seem to get the derailleur to go far enough across to clear the 3rd cog. I've tried everything, even following the video guide here step for step. Is it possible that my gear lever just isn't pulling the cable tight enough to get the derailleur to push away from the frame enough? Is there a setting or adjustment for setting how much the derailleur moves for each increment on the lever? At the moment 1st gear is fine, 2nd gear isn't too bad, but the chain can rub against the derailleur sometimes, depending what cog I'm in at the back. 3rd is just a no go. I've nearly got everything else on the bike sorted, but this is driving me mad :O(

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Looking at the photo, it looks a bit like the metal plate just below the plastic piece with the shimano sticker is bent in a little. If the cage is bent in a bit, that would be a pretty good reason for not being able to clear the 3rg cog, wouldn't it?

The screws on the derailleur should be able to move it farther to the right. Also you can adjust the barell up by the shifter. You could try tightening the cable to see if that does anything.
Now that I look at it more, it does look like that bend is bumping the chain off when a link passes by.

[JohnnyCO]

Every time you make an adjustment to your screws and barrel adjuster, shift the front derailleur down to second and then back to the large ring. This accepts the adjustment. It just won't happen without dropping it down and back up. To begin, I would put front derailleur in in small ring, and loosen cable bolt so its unattached. No cable tension now. Remove chain. Move the front derailleur with your hand to its high (large ring) ring. Looking straight down on it, the ring teeth should be right in the center of the cage. Do the same with the small ring, but sounds like that is already ok. Reattach chain. This should have ya in the ballpark. By the way grease those threads on the limit screws.

[RobAR]

Forget adjusting Limit Screws, calling Mister Shimano and everything Else.
The bend in the front of the outer plate is not the way it was manufactured. It was done deliberately. I would say that this bike, at some point in its life, was either raced, worked on by a racer or... we won't go there.
When I see that, it tells me that the person that did it knew that the mod would FORCE the chain down regardless of how muddy it was. It's a common mod made trail-side by potential top 3's in MTB races to make it to the finish line. Considered a sacrificial part. This is a prime example. No way did a rock jump up there and bend it like that.
Bend that plate back out straight, take the time (unless you are racing) to get the mud off and try it again with fresh cables. You might be a bit happier!