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Old 08-09-11, 04:15 PM   #1
jezmellors
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Chain slipping after replacing

Hi fellas,

i had a problem with the chain slipping on my 9 speed mountain bike, mainly on the smaller gears so i checked the chain, decided it was worn and changed it for a KMC X9 one, previous chain was Shimano. Anyway, i've been out on the bike today and the problem is worse, the chain slips in every gear now, i've checked back for related posts and concensus seems to be that the next place to look is the cassette but it looks fine to me. I took some pics and hopefully you guys can give me your opinions on the cassette if the pics are good enough.

The RD is quite old and the springs don't seem as strong as they were so i screwed the adjuster screw in all the way and the jockey wheels look quite worn too if either of these things are relevant.
Thanks for any help.
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Old 08-09-11, 04:23 PM   #2
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PS.

When i changed the chain i fitted it using the big ring to big ring without the Derailleur method. Just trying to think of everything which might be relevant.
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Old 08-09-11, 04:27 PM   #3
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What I see looking at the cassette is that on the smaller cogs the sections between the teeth look wider and shallower than the corresponding sections on the larger cogs. If the largest cog is number 1 and the smallest is 9, it looks to me like 4 is slightly worn and from 5 to 8 (can't see 9 with the chain there) are more worn.

When I had my cassette replaced it looked OK to me, until I compared it to a brand new cassette and could see the difference instantly.
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Old 08-09-11, 04:27 PM   #4
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If it's slipping in the back, then the cassette is likely the culprit; if in front, then the chainrings. Having the situation get worse when you put in a new chain is classic, as the old chain and cassette/chainrings wore in together.
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Old 08-09-11, 04:59 PM   #5
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I generally replace the cassette with the chain if it gets to the point that it's skipping as you pedal. Are the gears adjusted properly?

Nice macro photos by the way.
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Old 08-09-11, 06:10 PM   #6
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If the old chain was worn to the point that it was skipping, it's almost certain that the cassette is likewise worn, and will skip even worse with a new chain. New chains often skip on old cassettes even when the old chain didn't.

There's no definitive test, except to swap out the cassette and see if it solves the problem. If you have a friend with a wheel whose cassette is OK, swap the wheels for a minute as a check. If your chain runs on his good cassette, yours is toast.
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Old 08-09-11, 06:49 PM   #7
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I have had hundreds of bikes, and I rarely can visually tell when a cassette is worn out. OK, if it is really, really, bad, that is obvious. I use the skip test. Assuming the chain is fine (and yours is brand new) and the derailleur hanger is straight, its the cassette. Replace it. I frequently see worn cassette skipping on bikes, typically, the owner must have ridden it in just a couple of gears, as only a couple skip.

+1 To above, while a worn chain sometimes will work OK on a worn cassette, put a new chain on, and its instant skipping.
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Old 08-10-11, 05:58 AM   #8
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What FBinNY said (even without the pics, I feel it in the force). Park Tool CC-3 (or the like from another manufacturer). They're not too expensive, changing chains before worn will save you a few cassettes.
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Old 08-10-11, 06:54 AM   #9
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my commuter has roughly 7,000 miles on it with the current chain/cassette, and the only time it slips is when I have taken it apart for cleaning. Adjusting the limit screws will only affect the operation of the derailleur in the largest and smallest cogs. Small fine tuning of the rear dr can be achieved using the barrel adjuster where the cable attaches to the dr.

In my experience, chain skipping is usually caused by an indexed shifter that is very slightly out of adjustment. This skipping is generally more pronounced on the smaller cogs because they have less surface area to engage with the chain. This misalignment could also cause the accelerated wear on the jockey wheels in the derailleur.

I always have to adjust the derailleur position after re installing the chain on all of my bikes. Cables can lengthen, housings can wear, and jockey wheels degrade. I find myself adjusting my rear derailleur at least once a month simply due to regular wear and tear on moving parts. My constant adjustment is probably excessive, but I like it when my drive train shifts perfectly every time.
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Old 08-10-11, 07:49 AM   #10
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http://www.sheldonbrown.com/brandt/chain-care.html
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Old 08-10-11, 09:01 AM   #11
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There is no reason to adjust your limit screws. This is the most common and, frankly, incomprehenisible mistake... they are limit screws and the problems people try to solve by adjusting them never have anything to do with limits. I probably made the mistake when I was starting out, too, but it is still weird how often the mistake is made.

Anyhoo, yeah, if your chain is worn past a certain point, lets call it 'point NFG,' then the cassette is also worn to match and a new chain will not mesh at all with the new cassette. Get a new cassette and the problem will go away...

but since you fiddled with your limit screws you should probably start anew with derailleur adjustments, and, once set, do not touch the limit screws again until you have a problem with the limits of the derailleur movement.

So install a new cassette, go to ParkTool.com, find the instructions on derailleur adjustment, and follow them step-by-step and don't leave anything out.

Good luck!

Edit:

I just re-read you post and I think you might have been talking about the B-tension screw on the back of the derailleur, not the limit screws... well in that case forget what I said about re-setting your derailleur. But still look for info on how to set the b-tension screw, as it is unlikely that 'all the way in' is the ideal setup.

Last edited by DCB0; 08-10-11 at 09:06 AM.
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Old 08-10-11, 12:00 PM   #12
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Well thanks for the comments guys, i can report that i have just ordered a shiny new Deore cassette to go with my shiny new chain, you must admit though, the old one doesn't look bad.

In retrospect i think i let the chain wear too much before changing it and this has ended up costing me more money in the long run. I will learn this lesson and check my chains more often. A tiny part of me still believes that the cassette is fine and the fault lies somewhere else but we will see and i will post an update when i've test ridden the new one.
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Old 08-10-11, 01:44 PM   #13
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Quote:
Originally Posted by jezmellors View Post
Well thanks for the comments guys, i can report that i have just ordered a shiny new Deore cassette to go with my shiny new chain, you must admit though, the old one doesn't look bad.

In retrospect i think i let the chain wear too much before changing it and this has ended up costing me more money in the long run. I will learn this lesson and check my chains more often. A tiny part of me still believes that the cassette is fine and the fault lies somewhere else but we will see and i will post an update when i've test ridden the new one.
I try to change the chain on my commonly used bikes every year. I figured I wasn't using my MTB much so Iwent two years on my most recent chain... and now I have to find a new cassette too!
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Old 08-10-11, 02:30 PM   #14
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I think the problem is that i'm new to off-road cycling and don't realise how fast dirty bikes wear out. I have an old steel racing bike with Campag Mirage and i haven't changed anything, not even the chain since 2001, and she rides like a dream.
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Old 08-10-11, 02:38 PM   #15
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A chain needs to be replaced by the time any one-foot interval has stretched to 1 1/16 inches. If you replace your chains on time your cassette should outlast at least 3 chains.
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Old 08-20-11, 03:49 PM   #16
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Just an update, i fitted the new cassette and as predicted it now runs perfectly. Lesson learned. Thanks again guys.
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Old 08-20-11, 04:20 PM   #17
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A happy ending!
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