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Chain not engaging sprocket correctly
#1
Hi Everyone,

I'm hoping someone can help with a really annoying issue I have. I’ve recently fitted a new shimano Ultegra 13-25 cassette and ultegra chain to my racing bike. When the bike gearing is on the 52 at the front and the 19th (I think…4th in from the rear wheel) at the back, the chain doesn’t engage the teeth of the rear sprocket properly. The outer chain plate kind of sits on top of the sprocket tooth as the cassette moves through the 12 o’clock position then clicks into place as it moves beyond that. When I have the bike on the stand and the plate ‘beached’ if you like, on top of the tooth, I can manually push the chain over a mm or so and it falls into place okay. When I’m riding hard though, with high cadence or putting power down on hills, this ‘click’ magnifies itself a hundred fold and causes me to almost slip gears and miss pedal strokes. Any ideas why this may be happening. I’ve checked for tight links and I don’t have any problems engaging other gears, so I really don’t know what is causing the problem. I’m considering getting a new chain, but the one I have currently fitted is less than a month old and don’t want to spend unnecessary money.

Thanks
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#2
First guess is either that the rear shifting just needs a little adjusting or that the cassette may be worn. Sometimes you get weird effects when you mix new chain and old cassette or vice versa. But check the shifting first. Even though a new chain "shouldn't" have affected it, anytime you change anything, sometimes it needs a little tweek.
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#3
(03-05-2010, 10:52 AM)DaveM Wrote:  First guess is either that the rear shifting just needs a little adjusting or that the cassette may be worn. Sometimes you get weird effects when you mix new chain and old cassette or vice versa. But check the shifting first. Even though a new chain "shouldn't" have affected it, anytime you change anything, sometimes it needs a little tweek.

Thanks for the response, Dave.
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#4
I can't say I had the same problem but I sure had the same symptoms. Found out that a pin (rivet) was pushed too far out on the inner side of the chain. Probably the one used for splicing. It was caught by a tooth of the upper sprocket and the whole inner plate was pushed upward and outward so to sit on top of a tooth of the sprocket the chain was supposed to ride on. Why it happened on only a few sprockets? My guess is that some teeth are bent more than others... K7 was SRAM 10 12/32.

Rgrds
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#5
These components are engineered with extreme precision and you should not be experiencing this problem. Normally a month old Ultegra chain will not have a wear related incompatibility issue UNLESS your old cassette and/or chain rings are worn. A worn out chain ring can "kill" a new chain with surprising speed. Use a chain wear indicator to assess your current chain. Depending on the generation of cassette your are using, the 17 tooth and 19 tooth cogs may or may not be attached to a carrier together. If they are, there will be no spacing issue - it the offending cogs are not "tied" together on a carrier, it is possible that you accidentally inserted an incorrect spacer? If neither of the aforementioned problems are factors, then it could be that your high gear limit setting (little screw on the back side of the mech.) is off. The indexing accuracy of the gear changes are reliant upon this "starting point". If it is off, the maladjustment will manifest itself in the form of poor pulley placement under the cog which becomes progressively worse as the derailleur moves up the cassette to the lower gears. Also, if you happened to have removed your derailleur pulleys to clean them, make sure that you do not have the upper and lower pulleys reversed (this makes a huge difference). The lower pulley is also directional - so make sure its orientation is correct. Hope that helps. One question, does this happen in both the big ring and the little ring?
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