CHAIN WEAR

[mattheus]

Well a new chain will pull further off a worn chainring than new one so its a bit arbitrary at best.

Good point! But that suggests it's more of a test of chainwear+ringwear.

"arbitrary" - well, sort of .... a used chain has more wear than a new one. Not all scales are linear. (look at early work on the science of electricty ... tongue hurt ... finger feels nothing ... finger hurt ... )

[jb]

You also have the problem of a dirty chain having trapped crud in the link pins thus preventing it from stretching out fully. A good chain gauge needs to put a considerable amount of tension on the chain to squeeze all the crap out and get a proper reading. And, who wants to clean an old chain that's destined for the bin, just to get a good measurement - paraffin's expensive after all.

[fastrack1966]

PHEW, thanks everyone, I'll give all that a go when I have the time. Now I know theres more than two ways to check a chain!

[Chris Jeggo]

You also have the problem of a dirty chain having trapped crud in the link pins thus preventing it from stretching out fully. A good chain gauge needs to put a considerable amount of tension on the chain to squeeze all the crap out and get a proper reading. And, who wants to clean an old chain that's destined for the bin, just to get a good measurement - paraffin's expensive after all.

I would have thought that the considerable chain tensions produced by normal pedalling would prevent the suggested entrapment of crud. If it were to build up into an immovable layer then a good chain wear gauge would measure precisely the length that needs to be measured.
Here's a thought - if crud build-up were faster than wear then the chain would gradually get shorter. And further, if we could control the amount or quality of crud we could possibly balance build-up against wear and have a chain which lasts forever.
Aah - pipe dreams!

[jb]

You also have the problem of a dirty chain having trapped crud in the link pins thus preventing it from stretching out fully. A good chain gauge needs to put a considerable amount of tension on the chain to squeeze all the crap out and get a proper reading. And, who wants to clean an old chain that's destined for the bin, just to get a good measurement - paraffin's expensive after all.

I would have thought that the considerable chain tensions produced by normal pedalling would prevent the suggested entrapment of crud. If it were to build up into an immovable layer then a good chain wear gauge would measure precisely the length that needs to be measured.
Here's a thought - if crud build-up were faster than wear then the chain would gradually get shorter. And further, if we could control the amount or quality of crud we could possibly balance build-up against wear and have a chain which lasts forever.
Aah - pipe dreams!

Well yes, but when you stop pedalling it can creep back in to a certain extent. Enough to prevent simply measuring the length of a free hanging chain from giving an accurate reading. The forcing of a wedge into the links that happens on most gauges helps to negate this.

[Cyckelgalen]

I feel that comparing a used free hanging chain to a new chain is reliable enough. The old chain will have some grit while new chains come with a very thick coat of lube and I assume that the effect on chain length will be very similar on both cases. Also, I always test the chains after a thorough cleaning in a white spirit bath. They seem superficially degreased, no idea if the cleaning effect that extends to every nook and cranny.

If the lack of tension or load is a major objection to this simple test, you can always hang equivalent weights on both chains to stretch them out properly.

[mattheus]

Clearly we need laser-based (CMM-style) tech mounted on the chain-stay, leading to a head-up display in the cockpit.

[CJ]

I would have thought that the considerable chain tensions produced by normal pedalling would prevent the suggested entrapment of crud.

Well yes, but when you stop pedalling it can creep back in to a certain extent. Enough to prevent simply measuring the length of a free hanging chain from giving an accurate reading. The forcing of a wedge into the links that happens on most gauges helps to negate this.

Well no, I don't think that actually happens, not to any great extent, not with my regime of oil lubrication. I regularly measure chains by three methods, with a ruler on the bike (elbow on 3 o'clock pedal to keep the chain tensioned how it was when cycling), chain wear gauge that pre-tensions the chain and cancels out roller slop, and by hanging the removed chain on a nail. The methods don't give significantly different results. The reason I use more than one method is convenience: I use whichever of the first two comes to hand whilst the chain is still on the bike and then I want somewhere to hang the dirty chain anyway. And when the hanging chain is half a link out at the 50-inch mark, I know the chain is scrap but the cassette is good to use. The hanging chain is my gold standard test.

Perhaps with wax lubrication things would be different. Maybe wax does clog up the clearances with semi-solid crud-laden wax. I don't know, have never used wax. I'm sticking with oil, which does make chains sticky on the outside, but I don't care about the outside, so long as there's liquid oil on the inside!