just Replaced chain - jumping....chain too long or short?

I replaced my chain yesterday, a shimano DA 9 speed. This is the first time i have changed a chain myself.

everything appeared to go well - i counted the links on the old chain, made sure the new chain was the same number, and it went on fine.

i just tried to ride on my trainer and the chain was jumping. I had the impression that maybe the chain was too long - it seemd to skip every few rotations of the cassette....therefore i shortened the chain by first one link (still jumped) and then 2 links shorter, and the jumping remained. The "jumping" seems to occur where the chain enters the derailleur, causing the derailleur to kick forward and then back quickly, and the chain seems to skip over the cassette.

right now i am wondering what the problem is - specifically maybe the chain was in fact originally too short, and now i have only made the problem worse. but then common sense tells me it is probably too long, but i counted the links so carefully.

does anyone have any ideas what might have gone wrong?

 

Check you have the wheel securely in the drop outs.
Next adjust the cable adjuster at the rear derailleur, try a few clicke in first then try out.

 

if it wasn't a problem with the chain length have i now ruined my new chain by making it two links shorter?

 

could be a stiff link or if your using the connex connector you might have it installed upside down.

To match my old chain length I just lay it out on the floor and measure the new one next to it, easier than counting links.

 

if my new chain is 2 links shorter than the old one is it ruined?

 

No, just avoid "big=big".

Did you try the RD cable adjuster?

 

how do you mean "big=big"?

but seriously - i can still use that chain?

where is the RD cable adjuster by the way?

 

Depends on what you mean by "jumping". Two possibilities come to my mind...

Worn Cogs?
If it skips (chain rides over teeth on cogs) when you pedal hard, then it sounds like a worn cassette. If you don't replace your chain before it "stretches" too much, then you'll need to replace the cassette as well. With serious wear, you may even have to replace your chainrings!

Because those items are so much more expensive than a chain, I just replace my chain at the slightest sign of elongation ("stretching" is really a misnomer; it's not the plates that stretch, but wear of the pin/inner link interface).

A pair of links should be exactly an inch. So if you measure 12 inches, starting at the center of a pin, there should be a pin exactly at the 12" mark. If I see more than 1/32", I'll replace my chain. Dirt is the biggest contributor to wear, so keeping your drivetrain clean and lubed will prolong it's lifespan. I typically get 3,000 miles out 9-speed Dura Ace chains...but then again, I'm anal about cleaning my bikes.

Stiff Link?
If it skips at a certain spot on the chain, then it may be a stiff link. If it doesn't happen every crank revolution or it happens regardless of how hard you're pedaling, then this may be the problem. To fix it you can use the "loosening" section (upper placement) that many chain tools have, and push the pin of the offending link, ever so slightly.

Or...you can grab the chain with both hands on either side of the pin, so that the plates are between your thumb and index finger, then bend the chain back and forth. Again, don't do it forcefully, just do it enough to get the "stiffness" out.

 

I would put my money on a stiff link. When the stiff link enters the derailuer it forces it to jump forward. You will be able to figure out which link in the culprit by turning the cranks over slowly until the stiff link enters the deraileur and makes it jump forward. There a few fix it guides on the net which show how to fix a stiff link. Somtimes you can fix it by hand by bending the link laterally, pressing it with your thumbs to loosen the plates. If that doesn't work you can use a chainbreaker to put some pressure on the pins and lossen the link, being careful not to push the pins out.

 

Sounds like a stiff link to me also. Experience is a great teacher and you are just being taught. We have all been there. When g-clark talks about big=big, he is saying don't shift onto your largest chainring in front while the chain is on the largest gear in the back. You may not have enough chain to do this without damaging something since you shortened the chain.

Going big=big, or small=small, is not a good idea under any circumstance anyway, as there is excessive chain deflection which increases the wear of the cogs and chain. There are other less extreme gear combinations on your bike that will give you the same gear-inches as the big=big or the small=small gear combinations.

 

That sounds like a stiff link to me. If this is the first time that you have ever installed a chain, there is a good chance that the link where you joined the chain is stiff.

Another common problem after changing a chain that has had a lot of wear is a worn cassette. As a chain wears, it gets longer. That causes it to wear the cassette cogs to mate with it's new longer length. Then, after you install a new chain, the worn cassette cogs won't match it and the chain skips.

 

Not if you saved the links you removed. Just reattach the links you need, being careful that the ends of the pins are secure in the outside plates and you don't have stiff links. Use the chain tool to loosen stiff links. Use neighboring links as a visual and tactile guide to how loose you should go

 

I'm pretty sure it is a stiff link, so I will try and loosen it up.

I'm hoping my slightly shorter chain will be fine. I am only using this bike for the indoor trainer anyway, so it will only ever be on the little ring until january. I'm hoping as long as I don't go "big/big" it will be fine.

Otherwise I know for sure reinstalling the links I removed will be beyond my technical ability anyway, so it will be a case of "let's go and spend 30 euro on a new chain and start all over again!"

 

It's better to run with a longer than a shorter chain - a short chain might damage the derailleur - nothing happens with a long chain.


Rick

 

WTF Bully. If your old chain worked properly [before worn] why would you have assumed a new chain of the same number of links wouldn't have been OK

The bottom of the chain has very little tension so a stiff link can be apparent, as you describe, as it enters the derailleur. The skipping may also be caused by a SL but most probably by a worn cassette.

If you are using the reinforced pin to join the chain, in my experience, when the link is not pushed in far enough the link will be tight. The moment the pin is in the correct spot the link is loose.
Warning If the pin is not done correctly you always have the chance that the chain my come apart.

 

Yes, you've done it nearly all correctly, but your cogs are also worn out, you need to replace them too.

HTH

 

Also have you threaded the chain into the rear derailleur correctly, it is quite easy to miss the small guide on the top pulley and have the chain on the outside of it.

 

The cassette is fine....it's only 3 months old - looks perfect.

it's def a stiff link - i think the one i pushed in when i connected the chain. I'll try and loosen it, otherwise i have a new chain ready.

from now on I am only using those SRAM connector devices that negate the need for inserting a pin.....and you can take the chain on and off for cleaning.

 

Clean the protective grease off the new chain before fitting!

Take the bike to the bike shop and have them adjust the rear derailleur when you have the new chain on.

 

Careful there Bull, those quick connectors tend to wear out faster then the chain and they become noisy. Learn to use the chain tool and rivets, fast easy and fun.