ed 

When I look down at my rear derailleur, the cage kinda kicks slightly inward toward the wheel. The der. hanger is not bent. It's a fresh build, but the rear der. came off my other bike. I can wiggle the cage back and forth a tad, but the flex/play is not in the mounting bolt. It's in the parallelogram links. (10 month old derailleur)

The main thing that caught my attention was a "micro-chainsuck" incident that didn't really do anything. I was getting into big ring and the middle to outer last few cogs on the cassette. The jockey pulley next to the cassette is lined up just right with the cassette, but the bottom jockey is inward a little bit. So, long story short, the top part of my chain doesn't follow the exact line as the bottom side that is coming off the big ring.

Do I need a new derailleur because top part of the chain is not perfectly vertical to the bottom, or is it normal for the top chainline and the bottom chainline to be slightly different?

ed 

Here's pic's. It seems like it's nice and vertical when in the outer cogs, but middle to inner cogs...the cage leans inward.

seely

Doesn't look too bad to me, but its kinda hard to tell.

slagjumper

This tool threads into the hanger then you rotate it along the rim, You can apply presure with the tool to bend the hanger strait.

https://www.parktool.com/products/det...8&item=DAG%2D1

blue_neon

No, he said the hanger wasn't bent so the above post dosn't apply.

Chelbod- that looks really strange, probalby a problem with the lower jockey wheel maybe. You could have damaged/slightly bent the lower cage?

blue_neon

Also if you can ride the bike/shift no problem then dont worry about it. However you will probalby be feeling the drivetrain not as smooth now, or you could get chain skipping or bad ghost shifting.

You can however, aquire a new LX or XT deraillure off eBay for pretty cheap if it was a problem.

ed 

I'm pretty anal when it comes to my bike being set up properly. I'll probably just snag an XT and call it good. If it doesn't change anything, I will have still upgraded my derailleur and I can throw this one in for spare.

I'll update when I get it figured out for reference.

blue_neon

Well if your upgrading why not go XT .

Mostly new XT's here going cheap: clicky

ed 

That's funny, I think someone in the thread already said that...hmm...oh yeah, it was me. hehe

The reason I don't wanna go eBay is b/c they sell for around $35-$39. Usually for the M750's. (last yrs model) I can get the M750 from Jenson until the end of the month for $39 guarantee'd to be new, and I know it will get to me. You just have to have the coupon code from their advertisement.

Thanks for the help though. I appreciate the replies.

Jason222

Did you try tighting all the bolts? Might be a loose bolt alowing it to flex over.

ed 

The only bolt there is to tighten is the mounting bolt that attaches it to the hanger. The loose part that is allowing it to flex is the actual Parallelogram. The parallelogram is press-fit toegether with pins. It's not bolted together. If you wiggle it back and forth, you can see that the mounting bolt and bushing are all nice and tight. The problem is lower than that.

stapfam

Bits wear out on bikes and rear deraillers are one of the things that do not get checked for wear that often. If you have movement when hand pressure is used- then you have wear in the pivots. Some wear is acceptable but then it is decision time-- How much wear means trip is OK before a trip to the LBS and Bill time is up to you.

I normally use XT as there is not much price difference between the two- but XT does work better. I have to change rear derailler every year but last year bought XTR on an offer price. Stripped the bike down and had actually bought a new rear derailler- an XT. Took it back for a refund as The XTR had not worn at all. It is as good as new, barring the dings and scratches.

ed 

Actually sometimes when I backpedal in the middle cog it leans in enough to cause the chain to derail to the middle ring.

Like having a second front derailleur on the bottom side of the chain.

ed 

Okay...I got my new XT rear derailleur installed and it looks sooooo much better. I guess that old LX was just plumb wore out, eh?

It's funny, even with worn out parallelogram linkage the LX shifted basically flawlessly throughout its entire life. Still works fine, just annoying. And I hated the backpedaling derailment.

Notice the nice vertical cage:

Chrizz

quick off-topic post: what tyres are they?

ed 

They are my new Tomac Signature Kenda Nevegal 2.35" Stick-E tires.