New chain jumping...

Jun 17, 2012
6
0
0
Tokyo
#1
I got a new chain fitted at a bike shop today but it is jumping when I get up to a decent pace/effort. I've got a week-long ride from Tokyo planned from Thursday and want to make sure that the bike is running smoothly by then. Am a lot of a noob when it comes to bike mechanics, so am wondering what i should do now... Options as follows:

- I'll go back to the shop tomorrow and get them to shorten the chain by one link
- I'll go to the shop where I bought the bike (at Y's, one of their Trek models) and get a new cassette, which should fit the new chain better. Are they likely to stock one that fits my bike since there is no time to order one?
- or something else?

The cassette was bought at the end of last year, and wasnt used from Dec to April, but maybe 700 or 800 km by now. The teeth on the sprockets don't seem sharp and still have a surface on the top of them.
The chain was jumping in any gear at any speed when I first rode it today, but then improved at some gears after a while... should the same happen for all the gears if I ride it a bit more.
 

GSAstuto

Maximum Pace
Oct 11, 2009
945
242
103
tokyo
www.roadfixie.com
#2
1) Chain needs to match the group more or less. 9sp chains for 9sp group, 10sp chain for 10sp group, etc. I doubt you'd have gotten the wrong one.

2) Lower end cassettes (Ultegra and below) will last nearly forever. They're steel. If your bike is less than 5yrs old and you've kept some lubrication on it - the cassette will be fine.

3) 'Jumping' is generally caused by improper rear derailler adjustment. For some reason this seems to be one of the unsolved mysteries, yet, like Zen Meditation, the easiest thing to do - cause in reality there is very little to do. (Read the threads on derailler adjustment here). FE posted a really simple and good method in some thread.

4) A clean and well lubed chain will almost always shift better than a filthy, dry one. Makes sense, huh?

5) Unless you have a zillion km on your chainrings , they are probably ok too.

6) Riding a bike more will stretch the cables to their settling point. New bikes need a little breaking in (riding) for this to happen. So, in fact, all the finite adjustments at the shop with a new bike are pretty pointless.
 

m o b

Speeding Up
Jun 22, 2008
341
23
38
Bremen
cyclitis.wordpress.com
#3
It is hard to judge from the information on hand but as Tim stated, my best guess would also be that the rear derailleur adjustment is not correct.

Of course this can also be caused because of having bought the wrong chain for your set-up, but if the chain was installed by the shop where you bought it that is a rather unlikely scenario.

If the chain jumps in any gear I don't think that the length of the chain is the main issue. Problems because of chain length would occur, when the chain is extremely short (outer front and biggest sprocket rear) or extremely long (inner front and smallest sprocket rear).

Yes, many mechanics recommend to always exchange cassette, chain and front chain rings at the same time. It has been discussed endlessly in all bike forums of the world. This might be a cause for jumping of chain but I would guess that it isn't the root cause in your case. It might only engrave the situation.

If you do not feel comfortable with bike mechanics I would recommend that you visit a bike shop with a good mechanic, such as POSITIVO and let them adjust your rear derailleur.

Good Luck.
 

FarEast

Maximum Pace
May 25, 2009
5,528
538
193
Yokohama
#4
How old is the cassette?

To repeat what others have mentioned -

Normally if the chain or cassette haven't been changed in years they will wear together - replacing the chain with a new one will not fit the teeth on the rear cassette as they would have worn down and not mesh properly with the chain.

Golden rule is unless you are constantly monitoring your chain for stretch and replacing then you should replace the chain and cassette together.
 
Jun 17, 2012
6
0
0
Tokyo
#5
Thanks for the suggestions. I will have a look at the rear derailleur then... also, where is this positivo place?

The cassette was bought at the end of last year, just used in the last couple of months at 700km or so on it now.

Not sure whether i should also get a new cassette or not if it is still jumping too much to attempt a long trip... Is it guaranteed to gearshift well if I get a new cassette fitted alongside the new chain at a decent shop? Can i try to stretch it manually to accelerate the period of adjustment to the current cassette?
 

m o b

Speeding Up
Jun 22, 2008
341
23
38
Bremen
cyclitis.wordpress.com
#8
Not sure whether i should also get a new cassette or not if it is still jumping too much to attempt a long trip... Is it guaranteed to gearshift well if I get a new cassette fitted alongside the new chain at a decent shop? Can i try to stretch it manually to accelerate the period of adjustment to the current cassette?
No, you can not manually stretch the chain to "fit" your cassette. Chains stretch not because the metal plates get longer but because friction gradually worns out the pins, creating a tolerance between them and the "bushing" (if any).

Guaranteed solved with a new cassette? No. Still I believe the main cause is either rear derailleur adjustment or perhaps a bended rear derailleur adaptor. You need a special tool to check if the adaptor is straight and paralell to the sprockets of the cassette.

If you go on a week long trip and you are not too experienced in mechanics and you want to be sure that you don't have any issues on the trip I think that letting the bike check by a pro is your best option.

In case ou need to exchange the cassette: Chains and cassettes are spare parts that should be on stock. You might not get the same cassette spec (12/25 or whatever) or grade (105, Ultegra,...) but you will get somehing good to keep you riding.

I was a regular customer at the Positivo Shop and Nagai-San, the owner used to be a mechanic in Europe for a pro team (Fasso Bortolo). He is very good in fine tuning a bike and I have full trust in his abilities.

Of course any other good bike shop will do as well.
 

zenbiker

Maximum Pace
Mar 4, 2008
799
220
63
Chofu
#9
It's the season!

This happens quite a lot at this time of the year.......

Cue the music...

"Summer time, and the shifting ain't easy.
Chains are jumping
and a new cog to buy.
:bike:
 
Jun 17, 2012
6
0
0
Tokyo
#13
Thanks for the advice all. Wasn't having much luck improving it myself so took it to the small red road bike store (cant remember its name) just south of Takaido station on Kanpachi-dori. The guy should have it sorted by the time of my ride.