Chain Wear

davereo said:

I recently bought a chain wear indicator tool. The tool itself is very simple to use. It is two sided and measures .75 wear on one side and 1.0 on the other. I am planning on replacing my chain when it reaches the 1.0 of wear. Am I being to critical to follow this method? Are the nightmares rumored to overall drive train breakdown real if I dont replace a worn chain ASAP?
Just a side note in the past I have been replacing chains annually not really knowing if they were actually worn.

Those tools aren't very accurate at all. A better measurement is one done with a metal rule, measuring from pin to pin over 12 links. If the pin-to-pin dimension is 1/8" or greater the chain needs replaced. If you don't replace a worn chain, said chain will cause excessive wear on the cassette (and chainrings) which might mean that when a new chain is finally installed, it won't function with the worn cassette (i.e., the chain might skip). That would require buying a new cassette.

Disagree with Alienator here that measuring the pin dimension is more accurate. Seems to me that the important dimension for chain wear is the inter-bushing distance, since that measurement includes any wear on the OD of the bushings. After all, that is what interfaces with the chainrings and cogs, not the pins themselves.

The Park CC-3 gauge has worked well on the HG-93 chains I use. The measurement seems to correlate well with the standard measurement of pin-to-pin distance over 12 inches of chain. Rather than wait until the 1.0 limit, I replace the chain when it hits 0.75% wear. That's usually between 4-6K miles for me......the chain seems to last longer on a new cassette.

As to what will happen if not replaced in time. Yup, it surely will wear on the cassette which will lead to skip on a new chain. And generally it will wear out the 1 or 2 most commonly used cogs.

I think the chain wear tool works fine. As mentioned on the packaging (I think), take a measurement from at least 2 places on the chain and do not include a "missing link" or similar attachment point in the measurements.

Unfortunately, bushing dimensions are not the same across chain manufacturers. Some quality chains can come out of the box and show wear if a chain checker is used. It's the pins that locate the bushings, and the bushings have a couple of degrees of freedom. However, it's the pins that are applying the load to either the cassette cog or chainring, and it's that load point that you want to fall within chain wear specs.

The use of the checker appears to be the easiest method. I will use this gage and order new chains when the chain reaches .75 wear.

alienator said:

Those tools aren't very accurate at all. A better measurement is one done with a metal rule, measuring from pin to pin over 12 links. .

Have been using park chain CC-3 tool and caliper - for me the results are allways the same (at least with KMC and Shimano chains).

While we're on the subject of chain wear, I came across a wear test conducted by Connex:

http://www.cantitoeroad.com/uploads/landingpage/connex/Chainwear_Test_10_Speed_10-JUN-2010.pdf

Not surprisingly, Connex came out on top, so I'm a little suspicious. Do any of you have experiences consistent with these findings?

IMO, checking chain wear by any method is better than none and given that chains aren't that expensive, at least in terms of $/mile, I'd replace sooner rather than later. Nothing good comes of riding a worn chain.

A couple of points which need considering:

Firstly: We are getting confused here. Bike chains have no bushings (or rather the bushing is integral to the inner plates). The ROLLER is what contacts the chainrings and sprockets. Modern bike chains belong to the family of bushingless chains.

Secondly: The only dimension which affects the ability of a chain to mesh with a sprocket is the pitch (ie: pin-to-pin distance). Wear on rollers (either inside or outside) has no effect on the distance between chain/sprocket contact points. The only time roller wear may be important is if the rollers are so worn they could fail (the chain is long gone before this point).

To illustrate this consider a chain pulling on a sprocket. As it does so the play in the rollers is taken up as they are all pushed in one direction relative to their respective pins. As the play is taken up in one direction this play is canceled so that only pin-pin distance matters.

As Alienator mentioned, roller dimensions vary widely across manufacturers. Try using a CC-3 on a new Shimano and a new Campagnolo chain. Both chains will be good to use but my CC-3 will measure the new Shimano chain as already being half "worn". Shimano chains just have looser fitting rollers.

Chain wear indicators of the park CC-3 type (and that mentioned by the OP) all push the rollers in opposite directions, whereas the sprocket pushes them all in one direction. This always results in an incorrect reading of wear because it takes the play of one roller into account. The saving grace of this type is that it gives an overestimation of chain wear. In short, you won't damage anything by following the tool's recommendation (provided it measures the distance accurately).

The most accurate type of wear indicator is a ruler (because it is cheap), but one should measure over as many links as possible to minimise uncertainty in the measurement. One percent of chain wear (recommended replacement point) is only 0.005" in one pitch. If we measure 10 pitches then we're looking for 0.05" or 0.1" in 20 pitches.
Another good wear indicator is the Shimano TL-CN41 which is designed to push the rollers all in one direction (as the sprocket does) to give a more accurate reading of the true chain wear than the more common type.

tafi, thanks for explaining the issue with the CC-3 and similar gauges. Had heard objections to their use before, but never understood the basis.

I will continue to use mine, but will remember to check with the steel rule as a confirmation of wear before replacing the chain. As I mentioned before, I've seen a good correlation with the CC-3 and rule in the past.

Still have trouble believing that roller dimensions vary between chain manufacturers. If that were the case, seems to me that chainring/cassette wear and noise would vary a lot depending on the make of chain used.

tafi said:

.
Chain wear indicators of the park CC-3 type (and that mentioned by the OP) all push the rollers in opposite directions, whereas the sprocket pushes them all in one direction. This always results in an incorrect reading of wear because it takes the play of one roller into account. The saving grace of this type is that it gives an overestimation of chain wear. In short, you won't damage anything by following the tool's recommendation (provided it measures the distance accurately).

.

How big the play of one roller is? The chain wear of 1% is about (between 12 links) 3 mm. In my opinion the reading error (play of one roller) will be insignificant. At least i doubt that reading errors of measurement taken with ruler (if chain is on bike) will be any smaller.

catlike said:

How big the play of one roller is? The chain wear of 1% is about (between 12 links) 3 mm. In my opinion the reading error (play of one roller) will be insignificant. At least i doubt that reading errors of measurement taken with ruler (if chain is on bike) will be any smaller.

The measurement error--roller play and uncertainty in the measurement device--can be enough to show that a good chain is worn enough to need replacing. As stated earlier, I've had new chains that have shown wear with chain checkers.

alienator said:

The measurement error--roller play and uncertainty in the measurement device--can be enough to show that a good chain is worn enough to need replacing. As stated earlier, I've had new chains that have shown wear with chain checkers.

Maybe chain checker you used was defective.
Those chain checkers are basic laser cuted steel plates- asuming cain tool is not defective, uncertainty in device shoud't be an factor. The uncertainy of ruler can be about the same. Anyway i usually recheck the worn chains (according to park CC-3) with caliper (between 12 links). The results allways are very close. So i have no real reason not to trust chain checker.
(and those are 8 speed chains if that changes anything).
We are talking about chain wear of ~2..3 mm. I doubt that diference of roller play between chains can be big enough to seriously influence measurement.

Yes. All the chain checkers were defective. In fact, you've got the only one that reads correctly.

Doubt is obviously conclusive evidence.

alienator said:

Yes. All the chain checkers were defective. In fact, you've got the only one that reads correctly.

Doubt is obviously conclusive evidence.

But can you tell how big the diference of roller play of diferent chains is? Wait. You can not. All you know is that chain checkers are inacurete but rulers are not.

catlike said:

But can you tell how big the diference of roller play of diferent chains is? Wait. You can not. All you know is that chain checkers are inacurete but rulers are not.

I've not quantified and recorded variances in roller play between various makes and models of chains. With one make of chains, I have used chain checkers--more than one--that have shown wear right out of the box; however, a steel machinist rule showed no wear that could be differentiated from measurement error, i.e. the wear shown was within the noise of the measurement tool. The chain checkers were checked against other chain checkers: identical, as far as the eye could see, within brands. Others in this thread have also observed variance in roller spec for bicycle chains, and as has been clearly stated, chain wear is defined by the distance between pins. It is the change in that distance that is the result of wear. Rollers have to have enough "slop" to accommodate changes in inter-pin spacing while still meshing appropriately with cog and chainring teeth. As such, roller spacing is not the metric of interest.

No doubt your doubt carries great precision.

OK, in the interest of science, I got out my super-accurate vernier calipers (from Harbor Freight). Roller diameters were taken on three chains scraps (unused). The HG-93 rollers measured .302 inches, while the PC-991 and KMC track chain were .304. Also while measuring, it did seem as if the Sram rollers had more play than the other two, but didn't try to measure it.

Applying the same ultra-precision calipers to the CC-3 gauge, I noted a .010" difference between the 0.75 and 1.0 sides of the gauge. If that's close, appears the differences in roller diameters (on my samples) by themselves would cause a difference of .05% wear in using the CC-3. Would be interesting to hear results others get from measuring roller diameter on other chains, or measuring the CC-3.

So far, based on the chains I measured, seems to me the error the CC-3 gauge introduces is on the order of error I'd make in reading a steel rule. After all, the difference between .75% and 1.0% over 12 inches is only .030, so if I'm off by .010 when reading the rule (or my cheapo steel rule is off by that amount), I'm dealing with a similar error.

In summary, I agree that the pin distance over 12 inches is a more accurate indicator of wear than the CC-3 gauge, but OTOH it's easy to introduce measurement errors when using the steel rule too.

Nice work, dhk2.

dhk2 said:

So far, based on the chains I measured, seems to me the error the CC-3 gauge introduces is on the order of error I'd make in reading a steel rule.
.

exactly