cranky old dude

I replaced the chain and 9 spd. cassette on my commuter prior to the start of the riding season, some 273 miles ago. I shortened the new chain to match the length of my old chain link for link.

It was a slow start to the season and I've only really started putting any amount of miles on the bike over the last few weeks. Being that my fair weather commuter is a SWB recumbent, it took a while for my "Recumbent Legs" to get back into shape. Now I'm basically back up to speed on the bike.

Over the past couple of weeks I've noticed that occasionally the chain tends to skip a bit. It starts to shift off of the sellected gear on the cassette then reseats itself. This only seems to occur once every three or four miles.

Based on the above information, who can solve my problem? Feel free to ask me for any further details, I will answer them.

You may be suprised to see what the problem turned out to be. I'll verify if anyone is astute enough to figure this out, otherwise I'll post the fix in a few days.

RonH

Did you adjust the barrel adjuster at the rear derailleur? Maybe half a turn away from the direction of the chain skip/jump (when viewed from the back of the bike).
Is the derailleur hanger bent slightly?

Retro Grouch 

Sounds like a tight link to me. That's pretty common. If you prop up your bike and slowly turn the crank backward with your hand the tight link will usually reveal itself at the derailleur.

jdon

All of the above. Lube the chain well and wipe off the excess, check the derailleur hanger and then try the barrel adjuster. Small tweeks!

cranky old dude

As I ran through the problem in my head while riding into work today the barrel adjuster was only a prime choice for a few moments. The clues as to why I ruled it out are subtle but mentioned in my post. The barrel adjuster turned out to not be the problem.

Since I had to shorten the chain, a tight link was my primary trouble-shooting path. I'm just a hack of a mechanic (another clue) and such an issue would not be out of the realm of probabilities. As it turned out though, that was not the problem.

The chain has been lubed several times this season in fact I lubed and cleaned it just two days ago. The deraileur does not appear to be bent and the barrel adjuster was set properly.

buelito

if the large cog on the new cassette is smaller than that of the old one, you will have chain skip that appears in non-logical places and times and intermittently. If that is the case, remove a link and you should be OK... (that happened to me once, and it didn't make sense, but I shortened it and it worked)

train safe-

cranky old dude

I'll remember that, thanks.

However I changed out an 11-34 Shimano for an 11-34 Shimano.

DX-MAN

Since it only happens every 3-4 miles, it's because you're going in and out of the gravitational constant for your region.

cranky old dude

Damn! The DX-MAN is good!!

Now 'splain it to us in greater detail please.

2manybikes

It's a dirty shift cable. Clean the cable guide under the BB. ??

Did you re adjust the derailleur cable? Did you leave out a spacer behind the Cassette? A new casette might not go exactly where the old one was. It could be off right to left a very small amount. Did you not tighten the lock ring tightly?

jethro56 

Someone put an 8 speed chain in a box marked for 9-10 speed.

cranky old dude

This is a great list for me to save for future reference, but none of the above was the problem this time.

cranky old dude

Nope.

2manybikes

Someone you know has a voodoo doll of you and your bike. They keep moving the chain over?

2manybikes

You bump the shift cable with your knee? You accidentally bump the shifter?

BlazingPedals

I've seen the top jockey pulley getting worn and sloppy, which causes weird symptoms. Somehow I don't think that was it either, though. Um... another thing that sprang to mind: did you happen to have the chain twisted? Not that I know where that thought might have originated - I certainly have never done such a thing!

Retro Grouch 

One of my other favorites is misrouting the chain through the derailleur cage. There's sometimes a little tab that's easy (and embarassing) to overlook.

2manybikes

The wheel is not securely held in the dropouts. Not tight enough on the QR lever? Did you use a master link? Nine speed chains need a new pin every time you remove one? Did you use a new pin? Even if this is not the problem.

cranky old dude

Bingo!!!! Get that man a cigar!!

I was sitting on a rock with a rag in my hand slowly wiping down the chain trying to find a pinched link. With the chain nice and clean my gaze drifted back to the deraileur hoping to see a link not flowing smoothly through the cogs. Boy oh boy did that chain line look weird with the chain running around the back of the lower cog and then around the front of the deraileur crosspiece before going over the top of the upper cog!!

I took pictures and will add them tomorrow when I get home. The ride home will also be my "Test ride" to verify that all realy is well.

As I got stronger I spent more and more time in higher gears. That's when I started noticing the problem. I assume that the wrong thread-up caused one of two things to allow the chain jumps. Either the smaller cogs are more succeptable due to less wrap (fewer teeth) and a decrease in pedaling pressure would cause just enough slack to mis-align things enough to jump, or the small grooves I was starting to wear into the deraileur cage were starting to snag the chain.

Either way it was simply a case of stupid on my part. Fortunately, I don't think I damaged anything too badly...time will tell.

Thank you everyone for joining in. I'll be saving the answers for future trouble-shooting events.

JanMM

I love a happy ending.

Rowan

The thought came to my mind literally one post before I got to Retro's post. And it's only because of elimination of all the other possibilities, and the fact that I misrouted exactly like this when progressing the build on my Ti bike late last week.

cranky old dude

O.K. Here are the pics.

Oh, by the way...my bike mysteriously seems to be running much quieter and my average speed has increased dramaticly!!

Ooopsy





This is gooder....





Not too much damage

donheff

Looking at those pictures I can see how easy it would be to make the mistake but I am surprised that the improper setup would not be noisy and/or feel rough. With no obvious cues you could go a long time with the wrong setup.

Retro Grouch 

I'm not telling how I knew. Lets just say "I've seen that done before." and leave it at that.

leob1

It should have also made one heck of a racket when pedaling. I know it did on my wife’s bike when I did the same thing. The grove on the tab looks much bigger on polished aluminum.