Chain Wear

[CJ]

My Rohloff chain wear gauge is uncannily accurate, up to the mark and a new chain will run on the cassette, over the mark and it will skip, even if only on the favourite sprockets.

It was a Rohloff gauge that told me a brand-new (if remarkably cheap) chain was worn out already. But when I hung it on a nail, this chain measured exactly the correct length overall - it simply had rather sloppy rollers. Reluctantly I fitted it to the person's bike, where to my initial surprise it worked absolutely fine.

Then when I thought about it, I couldn't see any reason why sloppy rollers - within generous limits - should be a problem. I can't even think of any mechanism by which sloppy rollers might cause sprocket teeth to wear faster when the pins start to wear and that chain does start to actually get longer. That's the light-bulb moment when I realised that chain manufacturers have quite a lot of scope to make rollers more or less sloppy, which messes up the measurement of gauges that simply drop in-between the rollers.

So I simply added a little wedge to my Rohloff gauge, to shove in a chain link before inserting the gauge just ahead of it. Unfortunately I lost that modified Rohloff gauge so I can't show you a photo, but there are some gauges that do it right, e.g. Shimano TL-CN41, which uses an extra finger to push the 'zero roller' in the same direction as the roller ten links away that the gauge is measuring up to. So here's an image of that.

[Mick F]

39" steel rule hangs on a hook in the workshop.
I take it down and lay my chains against it.

Do you have to take your chain off to measure it? (I know you do this anyway as part of your cleaning/lubrication regime).

Yes.
I clean it first, then lay it on the kitchen table alongside the 39" steel rule. The table is a nice big pine one and I've plenty of room.

[Brucey]

.....Then when I thought about it, I couldn't see any reason why sloppy rollers - within generous limits - should be a problem. I can't even think of any mechanism by which sloppy rollers might cause sprocket teeth to wear faster when the pins start to wear and that chain does start to actually get longer. That's the light-bulb moment when I realised that chain manufacturers have quite a lot of scope to make rollers more or less sloppy, which messes up the measurement of gauges that simply drop in-between the rollers. ....

I agree that chains might vary significantly in this respect, and that is why such chain gauges are not ideal.

But I think that worn (or slack) rollers might wear sprockets and chainrings more quickly. My reasoning is that the roller makes a sliding/rolling contact with the sprocket on its ID and OD with each visit to the sprocket. There are three phases; engagement, loading, disengagement.

The first causes chain skipping if it goes wrong, but doesn't cause much wear because the loading is low. If the roller is a good fit, there isn't much movement during the second phase, but if there is play in the roller, there is a sliding contact on the roller ID as that chain link is loaded. With every other link disengaging from the sprocket the inner side plate rotates within the roller and causes further wear, more if the diameters match less well, because the load is concentrated. [This isn't quite balanced by similar wear on the other roller during chainring engagement, because the articulation angle is less in the latter case; in theory you should be able to tell which way a chain has been run by looking at its roller wear on the ID I suppose.] As the chain disengages, there is another contact movement like the engagement contact, but this time there will be load during at least part of the movement, as the load is passed on to the next tooth.

In all cases the roller will see higher loading and more movement if the roller is worn or slack on the ID. I don't know if this automatically translates to accelerated sprocket/chainring tooth wear too, but it might well do so. I think the effects are likely to be secondary to those produced by an elongated chain, but are similar in nature, if not perhaps extent.

cheers

[mercalia]

if u are going to use a chain wear tool , like the Park CC2 one I have, you really need first to "measure" a new chain & make a note. The instructions on my tool say that a new chain is some where between .25 & .5 and to replace at <= 1.0. This tool was bought 7 years or so ago & I am still on the same rear ( 8 speed ) block on one of my bikes, is still fine, I dont get any jumps with new chains.

http://www.parktool.com/product/chain-checker-cc-2

interesting the comments about 9 & 10 , 11 speed chains on the Park page

http://www.youtube.com/watch?v=I-iTruN8F3A

its interesting to measure a chain wear at differnt places to see how even or not the wear is.

[531colin]

Sixty or seventy quid for a wear gauge is a bit steep just to satisfy my curiosity.......does this one fulfil your criteria?.........http://www.bike-discount.de/shop/a102769/chain-wear-indicator-tl-cn42.html?lg=en&cr=GBP&cn=gb&gclid=CNq_nJiSqLoCFWTHtAodvHYAHg

Can you clarify this for me?

.................. In my case the choice of how much wear to call critical has been a matter of trial and error and has changed as I've adopted more accurate methods of measuring it (than the usual gauge). I used to think 1% elongation was okay, but after a couple of cases of a new chain jumping badly on a cassette recently vacated by a chain with exactly that much wear, I've dropped it to 0.5%. I don't always catch a chain at 0.5%, some get to 0.6 or 0.7 and sometimes there's a bit of new chain jumping on sprockets vacated by the latter - but usually only one or two sprockets and only for a short while. So I think 0.5% must be about right, as the amount of wear that lets you keep the old cassette. ..................

Does it mean some chains are OK at 1% wear, and some cause skipping at 0.6 or 0.7% wear? ....because that doesn't sound like a very useful measurement to me.
Or does it mean all chains cause skipping at 1% wear, and some do at 0.6 or 0.7% ?

[Brucey]

I think that not all sprockets wear as much as one another, and none are ever quite as worn as any single sprocket would be if it were the only sprocket in use. I think the sprockets are always playing 'catch-up' with the present state of chain wear.

I also think that smaller sprockets (if favoured) take more wear, more quickly, from an elongated chain.

They also have a shorter wrap-round which I think always increases the chances (vs larger sprockets) of skipping with a new chain, too.

So I can see how a 1% elongation might be OK in some cases, but equally how it might not be in others. If you use a few chains to 0.5% there is nothing to stop you from using them again later on from 0.5% to 0.75% etc, so you can get your money's worth out of them!

cheers

[freeflow]

If my understanding is right then loose rollers per se will not cause cassette wear. This is because the roller can be easily pushed out of the way by the cassette teeth using very little pressure. Wear will occur when the roller play is used up by wear on the plates around the connecting pin meaning that the roller cannot move out of the way of the cassette teeth.

[cycle tramp]

39" steel rule hangs on a hook in the workshop.
I take it down and lay my chains against it.
Any wear/stretch is immediately seen by the elongation at the 39"mark.

0.5% (3/16ths @ 39") is too far IMHO.
I go for 0.4% or less.

By that time, the chain is all wobbly and waggly.

But possibly still useable for those of us with hub gears and saucer sized sprockets.... there could be a whole second hand market in selling partly worn chains to hub gear users (some of us will simply smoother them in grease and lock them away in a dark chain case, where they can live out the rest of their service life in luxury...)

[Mick F]

Excellent idea!

One of my 10sp Campag chains has done 6,100miles, I may be able to squeeze another 500miles out of it, maybe even get it up to 7,000miles. Perhaps I'll put it up for sale one here in the future.

I don't think there's much of a market for old chains at the moment, but it could catch on.

[Edwards]

But possibly still useable for those of us with hub gears and saucer sized sprockets.... there could be a whole second hand market in selling partly worn chains to hub gear users (some of us will simply smoother them in grease and lock them away in a dark chain case, where they can live out the rest of their service life in luxury...)

Not from me as I change the chain when the gauge says 0.5 and keep them. They will be fitted when a new chain starts to jump, when they will be run to 0.75 (on my Park gauge)

[Brucey]

used chains for IGH's.... tee hee.

My IGH machines get as many new chains (new chains that are 1/8" wide and can be worked easily with a chain tool, to boot) as they want, for less than £2.50 each....

cheers

[jb]

Chain life can be extended by some 34.2% by removing all the pins and puting them back at 180 degrees

[Mick F]

I'll send you mine for you to do for me.

[mig]

Chain life can be extended by some 34.2% by removing all the pins and puting them back at 180 degrees

that's very hot to be messing about with chains in such a way.

[CJ]

Chain life can be extended by some 34.2% by removing all the pins and puting them back at 180 degrees

Only if the pins are irony ones.