Bicycle Mechanics - Chain jumps after...

Thought I'd share something I just learned.
New chain jumps on the old, wore out rear cassette.
Just bought a new front chainrings and chain, but didn't believe when at LBS they said that chain will jump over with the old cassette.
Well, as soon as first two components were installed and I went for a ride... chain was jumping very badly.
Every full pedal turn...
Getting a new cassette now. six gears 12-28 originall, or maybe 12-32, if deurailler will allow, haven't decided, yet.

Such an experience...
http://www.caree.org/images/Bikes/components/shimano_ultegra_9cassette.jpg

Yep. Read the section under "chain and sprocket wear".
http://www.sheldonbrown.com/chains.html

Yeah, I 've read that entire site before, but don't recall mentioning jumping chain...
That's why I share this experience.

It is common knowledge that the rear cogs wear with the chain and that if you dont replace the chain before a certain point you will need to change the cogs also. THere tons of threads on this very site about it.

Originally posted by Inoplanetyanin
Yeah, I 've read that entire site before, but don't recall mentioning jumping chain...

Quote from Sheldon's page:
"The worn teeth have become ramps, causing the chain to ride up under load. "
Hence, the jumping chain.

All right, dude!

Brought this thread back up!
After installing new front chainring and new rear casette, AND NEW CHAIN, it still jumps!
I blame the chain to be the wrong type. On the box, it said to fit singlespeeds and bmx, LBS worker was claiming it to be the right one, but if I look closely, the chain links are TOO far apart for the rear casette....

Anyone familiar with such problems?
Any ideas will be payed attention to.

Thanks in advance.

I don't know if this is true or not, but when I was at a bike shop asking them to install my new chain on the bike, they told me not to do it because the chain would jump on the old cassette. So they told me to get a new cassette. I almost insisted they put the chain on anyway, but they told me that if I did, it would wear out my new chain faster, so don't put the chain on the bike until I get the new cassette to put on the bike too.

Did you ride around with the new chain on the old cassette for a bit?

Koffee

Mr. Ino.........The guy at your LBS sold you an 1/8 inch BMX chain instead of the standard road width chain of 3/32 inch!!! These chains are too wide for multiple cogged cassettes!! Errrrrrrrrrrrrrr....!!! Where do they get these people???!!! If I were you, I'd send one of Saddam's sons to pay this person a visit.

According to the Barnett's chapter on chains, and having worked on a small fleet of hire bikes, plus my own, there could be several reasons for the symptom.

But the most obvious, of course, is to check that the shifting mechanism is properly adjusted. This is the source of most problems like this because the derailleur is allowing the chain to rest against the adjacent cog or its ramps, and the chain is trying to change gear all the time as the ramps/teeth lift it up. But it doesn't quite engage. Barnetts has a chapter on adjusting rear derailleurs.

Check your cable. Is it clean and lubricated within the housings, or rusty and dirty? At the derailleur end, is there any fraying (an unwound piece of cable can go back into the housing and interfere with movement on changes)? Did you clean and lubricate the derailleur? Do the jockey wheels still have teeth similar in shape to those on the cogs, or are they pointed (if so, they need replacing)? If you disassembled the rear derailleur, did the right jockey wheel go back in the correct place (there is more freeplay on one than the other)?

If you installed the chain yourself, did you make sure the rivet was centred between the two sideplates? A protrusion of a rivet on the inner face of the chain may cause jumping as it engages on the ramps of the adjacent cog. Likewise, you may have a tight link from installing the chain. You can loosen the link by sideways flexing the chain with your hands, or pushing the corresponding rivet back in the opposite direction to its installation by a 1/64 or 1/32 turn of the chain tool.

It may be that you have a chain that is incompatible with the derailleur gears. Wide chains are, according to Barnetts, not generally sold these days. The narrow chain has a rivet width of 7.4mm. You can measure this with verniers, or even a compass with two needle points. The supernarrow chain for nine-speeds ranges from 6.6 to 6.8 mm in width, which probably isn't relevant to you.

Barnetts states that there are two types of chains with different *pitches* (as opposed to width) -- 1/2" x 3/32" for derailleur bikes, and 1/2" x 1/8" for non-derailleur bikes. Yours is a derailleur bike.

You may need to check the box again to see if there is pitch specification on it that corresponds with either of those specifications. That will give you an idea of what you are dealing with and whether to return it to the shop.

Draw up a checklist of these items perhaps starting with the pitch of the chain and whether this is on the box. Go through each, one at a time, and tick them off. I think a wise contributor to this forum recently stated something like: It's a process of elimination.

Others' opinions may vary.

R

Thank you Rowan, George and Koffee Brown.
The casette is new, the deurailler was not causing any problems before and is in good condition. Cables are new.
I was doubting about chain being wrong, but seller insisted.
I will go to the shop tomorrow and will exhange the chain, if it will not fix the problem, new deurailler will be purchased as well. :)

Thanks for information! I will see how it goes tomorrow. :)

Originally posted by Inoplanetyanin
I will go to the shop tomorrow and will exhange the chain, if it will not fix the problem, new deurailler will be purchased as well. :)

Mr. Ino.......forget the derailleur. This is a slam dunk wrong chain issue!
I live in L.A. too.....so what part of town is this LBS located???? I'm just curious. No need to name the shop.