Chain wear - strange pattern

[Davidc]

The mtb I use for local trips has a Shimano HG50 chain. Nothing special, reasonable quality basic chain.

When it had done just under 1000 miles my chain guage showed 75% wear. I made sure I had a spare in stock. I'd have expected to replace it at about 1250 to 1300 miles.

It has now done 1600 and appears to have not worn at all in the last 500 miles.

It's not important, but what's going on? I don't understand why this unusual wear pattern has happened.

 

[Paul_Smith SRCC]

A dirt gritty chain will wear very quickly, perhaps as you have been monitoring it more closely that could mean that you have also been cleaning it at the same time?

Paul_Smith
www.corridori.co.uk

 

[oysterkite]

Chains wear disproportionately initially with most wear taking place in first few hundred miles....

 

[mickle]

Are you measuring it in the same place each time? I don't mean the same place exactly - are you measuring 'inner link to inner link' or 'outer link to outer link' each time?

Do you know what I mean? ... not sure I explained that v well.

 

[Moodyman]

Damn - You got me thinking now David.

I replaced mine last week at 1/16" past the 12" mark - done 1600 hillyish miles.

I now wonder if it could have plodded on a little further. I'd have preferred changing it in Spring.

 

[PpPete]

It could have been close to the 0.75% wear mark when it was new - just on manufacturing tolerances

 

[marzjennings]

I can't help you there as I usually replace my chains at .75% wear. All I know is that after that point the chances that I'll need to replace a cassette as well as the chain, when the chain needs to be replace, start to climb.

 

[Davidc]

Thank's for the comments, interesting ideas.

The measurements are done with a Park Tools guage, so it only fits one way. It measures from the back of one of the rollers in effect to the the straight end being in front of another one further up the chain, the 0.75 or 1.0 measurement being valid when the pointy bit slots into the gap. The section of chain being measured is random.

When new the chain was certainly below the 0.75 length, but no idea by how much.

I can't say I'm losing any sleep over it, just a curiosity I've not seen before. I'm not too worried about the cassette this time as I'll be replacing it with a generic trade Shimano compatible one at the same time as the chain. If it was a newer cassette I'd probably have already changed it but as long as it doesn't damage the chainset or jockey wheels I'm not too bothered.

My practice when changing drivetrain bits is to change the chain between 0.75 and 1.0 twice after renewing the cassette, then the third chain stays on well beyond the 1.0, wrecks the already worn cassette, and it and the cassette get changed as soon as they make a noise or get sluggish changing gear, or (on the tourer at least) before a long ride. The main risk is chain breakage but it hasn't happened to me yet

I don't think dirt or grit is much of an issue, the chain gets maintained with a regime similar to the Mickle one, in bad weather at least once a week and in good weather about every two weeks. This time of year quite a lot of gunge comes off during the wiping phase.

If they don't give up on me sooner I'll replace the cassette and chain when I do my annual total cleaning, usually end of March time.