davidonabike

So I did my big overhaul (New crank,BB, Cassette, and chain), all the youtube videos and a genuine bike repair book will not help me properly setup the rear derailleur. I think after two evenings of messing around and not getting the rear derailleur to shift properly I think it's most likely the fact that I replaced a chain for the first time in my infancy of fixing my bike, and think despite watching a youtube video of the process, made it too short. When it's setup the best with the new chain, it will skip a cog, jump around a little, and depending on the cog will sound like its trying to shift… There are so many variations as well, some that use the barrel adjusters and those that don't. Either way, looking at the jockey of the rear derailleur, it looks like it's far too stretched out. But I don't really have a frame of reference. All the youtube vids and pictures in the book are so close up I can't tell. Below is a picture of the derailleur with the biggest chainring and largest cog. If its not the chain hurray, I've saved $80…. Thanks in advance for any help.

Velocivixen

I'm relatively new to bike wrenching and have replaced several chains with the help of the Park Tools website and my local bike shop mechanics. In my opinion your chain looks too short. I'm under the impression that your bottom derailleur pulley should be facing down at about a 45 degree angle and there should be at least a slight curve between the upper & lower pulleys. Yours looks really stretched out straight.

davidonabike

I imagine you're correct. Thanks for the advice. Park tools seems like a more reputable place to look first rather than a youtube video. Oh the humanity!

Andrew R Stewart 

Learn to seperate out he various factors in doing repairs. Chain length is independent of der limits or index corridination. Move the der across the cogs first with only your hand or just the cable. Then move onto the cable tension/index stuff.

Yes, the chain looks to be well too short. Andy.

Reynolds 

Looks like the chain is on the 2nd sprocket in the pic, if so it's definitely too short. But that shouldn't keep the derailleur to work OK in less extreme combinations. Make sure to set the limit screws correctly, take up cable slack with the derailleur on the smallest cog, tune indexing with adjuster barrels.

hueyhoolihan

a too short chain like that will act just as the OP described it. if the OP has read all the literature and still can't make heads or tails of it, he or she should just add a few more links and repeat until the chain will move on to, but not over, the largest cog. that would be a good starting point.

and it wouldn't be a bad idea, in addition, to give that cage a bit of breathing room too. if it had eyes, they'd be bugged out!

davidonabike

Thanks for all the help! I've since bought a new chain, it was a difference of an inch worth of links. The bike is now purring like a kitten . Using the barrel adjust to do the final indexing was a big help. A lot of resources skip that step.

Camilo

If you're in doubt with a new chain, learn to use the "big-big" method of sizing. It's totally simple, objective and you won't end up with a chain that's too short.

How did you size the chain originally?

rpenmanparker 

Try the large front-small rear combination. If the two jockey wheels make a straight line perpendicular to the floor, the chain is close to the right length. If the pulleys slant forward , the chain is too short. If backward , the chain is too long.

davidonabike

The method I used was small chainring to small cog, and aligned the chain until the deraileur/travel of the chain enough clearance from the jockeys. However, the first time I had the second jockey at a 90 degree angle, basically an inch or two too far. The second time I was very nervous but was committed to the method.

rpenmanparker 

I'm talking about fully threaded through the RD.

davidonabike

I did a poor job of explaining. Yes, I fully threaded it through the RD. It was where you're to gauge the length I made the misjudgement. I measured twice what looked to be good, but was very wrong.