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Chain Checking

by roadbikepilgrim
Sat, Jun 06, 2020 07:17
5

Here is one for the obsessives (and there is nothing wrong with that). Those who get 10,000 miles from each chain can skip this one 😉.

Yesterday I checked an 8-speed SRAM PC850 chain for wear. I had done circa 7 months and a week on the chain. Chain wear tool used was Decathlon's.

Previous two chains were KMC Z series, from which I probably got eight months wear each on the bike's original Sunrace cassette, but through inexperience waited rather longer to change chains. This resulted in initial skipping, which quickly settled. However, I vowed to the bike chain gods that I would keep more on top of this.

The SRAM chaib was fitted on a new Shimano HG50 cassette as part of a stock wheelset to Shimano RS10 upgrade. I have been checking for wear religiously, and yesterday the checker tool mostly showed a still-reasonable amount of life in the chain. I know life is not linear with a chain, but I thought that I could keep checking until the 9-month mark.

However, I always check the whole length of the chain, and I found that either side of the quick link the tool was showing the chain almost worn. Although 90% of the chain still appeared to have life, I erred on the side of caution and changed to a KMC X8 chain, which I am trying for the first time.

Was I being over-cautious and should I have waited longer until there was more wear across more sections of the chain?

Should I get a better tool than the £3.99 Decathlon one?

Thanks and regards

roadbikepilgrim

If you're new please join in and if you have questions pop them below and the forum regulars will answer as best we can.

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5 comments

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Organon | 3 years ago
0 likes

I have no idea how someone would get 10KK out of a chain. I used to do this back in the day this would take me two and a half years and it would ruin my cassette and crank for the new chain. The pain of changing a crank was not worth it. Nowadays I *try* to do 10KK a year and the idea of changing my whole drive train is unthinkable. I *try* to change my chain every 2500km, but often forget to check.

If chain preservation requires pootling around at granny speeds though, I am not interested.

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roadbikepilgrim | 3 years ago
1 like

Thanks everyone for your input. I had measured the old chain crouching on the ground in my hall, without great natural light.

Today when the bike was in the stand in my kitchen, I could not fight my curiosity, and I put the old chain back on. I was quite surprised to see that the tool was not dropping nearly as far in those "dodgy" links near the quick link as I had thought, and wear seemed almost even along the chain.

I know that the chain is not directional, but I wondered if it is now reversed and this makes a difference. Or some sort of low-light parallax distortion was operating in my hall 😂? Quite weird, but I shall now use it a little longer. This is not to save money, but to see if I can trap the  go/no go moment on the chain in relation to how long it has been on the bike.

On the two KMC Z chains that preceded the SRAM, although I was checking stretch pretty regularly, I missed this point. The chain seemed to go from having life to being shot without my being able to trap it. I am curious to see if the SRAM PC850 will last longer than the KMC Z, and in the future to see if the KMC X will last longer than the SRAM.

My bike is not worth spending money on high end chains, but I wanted to move away from B'Twin-badged KMC Z chains at £8 a pop from Decathlon to a more mid-range option that offers a nice balance between price and extra longevity.

Cheers,

roadbikepilgrim

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TheBillder | 3 years ago
1 like

This raises some interesting questions about engineering tolerances and how the chain tools are made. We expect them to be accurate when measuring 0.75% wear, but what does that really mean? When I measure (with the Park tool) and find mine is end of life, I'm not going to instantly condemn the chain, but I will order a new one. It won't stop me from riding until it arrives. So might my chain be at 0.9% at that stage? Is that knackering rings and sprockets? Not so far.

If anyone can do this for £4, Decathlon can, but how is the tool made? Can a pressing (cookie cutter style) can be all that good? I assume that's how they are made.

I also look after my partner's hybrid (3x8 speed), which is little used and a cast off given to her years ago. The Park tool doesn't drop into the gap between rollers, but only because the chain is so worn that the next roller is in the way. Huge amount of sideways movement as well, but somehow it all still works. So perhaps you can get away with a bit more than you think, and perhaps I should get on and replace it today - but will the new chain work with the rest of the drive train?

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Drinfinity | 3 years ago
2 likes

You are doing just fine. A chain is a consumable item, and you are probably spending about 50p a week on it. 
You could have left it longer, which would have saved £1, maybe £2 in the year on chain. It would however cost another £20 on a worn cassette, and maybe up to £40 on chainrings. 
No doubt someone will come and link to the article which describes how a standard chain checker isn't really measuring the right thing and they can get 73.6km more from each chain by using a £20 device that will pay them back after 10 years. Which is fine if your hobby is making chains last longer than anyone else on the internet.

My hobby is riding bikes, so I change my chain every time the road.cc article on "should you change your chain" is published.

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hawkinspeter replied to Drinfinity | 3 years ago
2 likes

Drinfinity wrote:

No doubt someone will come and link to the article which describes how a standard chain checker isn't really measuring the right thing....

Here you go - the chain wear measuring article: http://pardo.net/bike/pic/fail-004/000.html

Personally, I just use a Park Tool chain checker and only bother with a single measurement (I don't bother doing the whole chain). I usually aim to change a chain when it's gone past the 0.5mm wear point but I only measure it very infrequently. I think as long as you change a chain before it hits 1mm of stretch then you're not causing too much wear on the cassette.

You'll be fine with however you're measuring your chain - you can use a ruler if you're careful. If you want chains/cassettes to last longer, then keeping them clean is paramount.

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