Chain wear

[yello]

My chain (KMC 10 sp) has done 7600km. The Park Tool gizmo doesn't drop in at .75 let alone 1.0. Measurement with a steel rule shows a gnat's crochet over 12" for the nominal foot. So chain would seem ok despite it's mileage. (mickle method btw)

Yesterday, I had a couple of slips on the cassette and a drop inside the small chainring (done that a few times recently). No signs of wear on cassette or chain rings.

Whaddya reckon? Change the chain and see what happens?

 

[swee'pea99]

Impressive mileage.

The Ultimate Authority, Sheldon Brown, say:

On a new, unworn chain, this rivet will also line up exactly with an inch mark. With a worn chain, the rivet will be past the inch mark.

This gives a direct measurement of the wear to the chain, and an indirect measurement of the wear to the sprockets:


If the rivet is less than 1/16" past the mark, all is well.
If the rivet is 1/16" past the mark, you should replace the chain, but the sprockets are probably undamaged.
If the rivet is 1/8" past the mark, you have left it too long, and the sprockets (at least the favorite ones) will be too badly worn. If you replace a chain at the 1/8" point, without replacing the sprockets, it may run OK and not skip, but the worn sprockets will cause the new chain to wear much faster than it should, until it catches up with the wear state of the sprockets.
If the rivet is past the 1/8" mark, a new chain will almost certainly skip on the worn sprockets, especially the smaller ones.


I personally would trust that, and also monitor the slips 'n skips situation. One or two is too few to base anything on, but if it becomes a habit...

 

[frank9755]

My chain (KMC 10 sp) has done 7600km. The Park Tool gizmo doesn't drop in at .75 let alone 1.0. Measurement with a steel rule shows a gnat's crochet over 12" for the nominal foot. So chain would seem ok despite it's mileage. (mickle method btw)

Yesterday, I had a couple of slips on the cassette and a drop inside the small chainring (done that a few times recently). No signs of wear on cassette or chain rings.

Whaddya reckon? Change the chain and see what happens?

I'd change it. It's had a good innings!

 

[yello]

I'd change it. It's had a good innings!

That was kind of my thinking too... and honourable discharge sort of thing!

I know it passes the technical checks (the "gnat's crochet" is less than a 1/16th btw) but maybe there are other fatigues than could lead to problems or, worse still, failures??

 

[yello]

I changed it... then ended up putting the old one back on! I was getting chain slip on the cassette in 4 or 5 gears.

I checked that I'd not reassembled the cassette spacers in the wrong order (I'd removed the cassette to clean it) but I hadn't, all was good. So I figure it was just 'new chain, old cassette' syndrome.

So I'll wear the old chain out completely then change both chain and cassette. I seem to recall there's someone on the forum that does that as a matter of course. That is, rather than rotating chains or changing chain only at lesser mileage (to try and prolong cassette life). I think they concluded that, cost wise, there was bugger all in.

 

[zacklaws]

Yesterday, I had a couple of slips on the cassette and a drop inside the small chainring (done that a few times recently). No signs of wear on cassette or chain rings.

Is it possible your rear mech needs reindexing or adjusting, sometimes I get that if its out of synch and it try's to jump onto another sprocket.

But looking at the mileage, thats good and I would not be surprised if the chain is wore out.