New chain skips when old chain was replaced at 0.75% mark

Question

I have a 3x8 hybrid bike that I use for commuting. I clean and lube the chain about every 200km, and regularly check it for wear using a chain cheker. I usually manage to ride between 1300 to 1600 km before the chain wears out beyond to the 0.75% level, at which point, to my understanding, an 8-speed chain requires replacement.

The problem is that every time I've tried replacing a chain that was worn at the 0.75% level, the new chain skips on all hub sprockets, even though these never look particularly worn out, and even at low load. As an example, see the attached photo with the latest worn hub.

Every time, this forced me to keep riding with the old chain until it broke, usually between 3000 and 4000 km, and then replace the entire drivetrain.

I tried changing the chain earlier, and so far I've got it down to 1200 km, but the issue remains.

Contributing to chain wear are the following: I am over 190 cm tall and weigh over 100 kg; I live in northern Europe, where the climate is rainy from autumn to spring and the grit on the road is granite or other hard stones; I often carry my son in a trailer, adding 40+ kg of pulled weight.

• In your experience, is it normal that an 8-chain skips at every turn at the 0.75% wear level?
• If so, given the information above, when would you suggest me to change the chain to avoid wearing the hub down?

Answer 1

To me, that looks pretty worn. My guess is that as the chain elongates, it grinds further into the gear valleys, making the "flattened" profile. The chain and cassette become mechanically paired, wearing together until the chain breaks. The cassette longs for its lost chain and will not take another mate... er, is mechanically incompatible with other chains. The wider profile probably leads to periodic instances of 2 rollers in the same gear valley, sort of riding the top of the valley and unable to lower a single roller.

So, options... 1) Clean frequently, and maybe consider a different lube. Lube minimally, just on the rollers. I use Muc-Off dry ceramic for our gritty trails, but it's very dry here. I have no idea how it'll handle your wet grit. 2) Replace the chain sooner.

For comparison:

Answer 2

I have no experience with 8-speed chains. However, seeing as your question has been up a while, I'll attempt to answer from general principles. Forgive me if you've already thought of the issues, but I don't know exactly what you know.

Chain maintenance guides such as the one written by Cyclingtips and Park Tools suggest that 11s and higher chains be replaced when they hit 0.5% wear. For 10s and lower chains, Park Tools explicitly says "replace your chain as it nears the 0.75 percent mark."

Thus, in theory, you should not have worn out your cogs if you replaced your chain before 0.75%. If you check frequently and replaced the chain the second you noticed it was 0.75%, I would normally think that this should also be sufficient to avoid cog skipping. This assumes you took a new chain and a new cassette, then you let the chain wear to about 0.75%, then you put a new chain on as soon as possible.

Assuming you did this, this raises some possibilities. First, the Cyclingtips article says, emphasis mine:

It’s important to know that chains rarely wear evenly across their entire length. And so however you choose to measure your chain wear, you should do it across three to five separate sections and use the highest measurement. And avoid including the quick link or similar joining link in your measurement as these often have slower wear rates.

Basically, do this to ensure you're measuring chain wear accurately. It might be worth checking the technique you're using to measure the chain. Also, put the chain tool in the top span of chain - this is the span that's under tension, and you'll get a more accurate reading.

Because your post implies you have had this happen a number of times, it's also possible your chainrings are worn out. If they are, that could be accelerating chain wear.

While I'm nowhere near your combined weight and I ride mostly in fair weather, it's true that riding in the rain accelerates chain wear. Basically, when it rains, you spray water plus road grit into your chain. This grit gets between the pins and rollers inside the chain. It combines with your lubricant to form a grinding paste. This wears the chain out. If you somehow don't have fenders installed, they do reduce the amount of water getting sprayed onto the chain (and your bike, and your own back).

In fair weather, we all can be less vigilant about cleaning - you would likely be fine just wiping your chain off with a rag after every ride, and lubricating it at the interval you stated. If you ride frequently in wet weather, I'd assume you need to be much more vigilant. I don't know how you clean your chain. Cyclingtips has a good article on chain cleaning. You can (and probably should) ignore the bits in the article about detailed or obsessive drivetrain cleaning. However, if you don't already have an on-bike chain cleaner (e.g. the Park Tools CM 5.2), I would highly recommend getting one. You can also consider getting a re-usable quick link, and removing the chain to shake it in a bottle filled with degreaser (NB: you can purchase degreaser in bulk, and you can likely dilute the degreaser when you do this). You may need to pay more attention to cleaning off the rest of the bike as well - for example, your cassette is relatively dirty. The grime on the cassette is likely dirt mixed with lube.

If you do intend to ride at a relatively leisurely pace but frequently in wet weather, you may actually be a better candidate for a bike with an internally geared hub and a belt drive. I'm not as familiar with this setup, but while they do sacrifice some mechanical efficiency, the gears are sealed in an oil bath. The carbon belt is not vulnerable to external contamination in the same way a chain is.

Answer 3

You're doing something wrong.

Firstly, good quality chains with proper care schedule should give 4000 km before they wear to 0.5% limit. You getting only 1300-1600 km before chain wearing to 0.75% limit (higher than 0.5%), means there's something wrong in your chain care schedule. My chains are nowhere near "breaking" (assuming this means catastrophically breaking in two) at 4000 km when they show 0.5% wear.

Secondly, you should be using 0.5% limit when deciding when to throw away the chain.

Some possibilities:

• If you're using particularly cheap cassettes, they can be made from low quality steel, thus accelerating their wear when used with a worn chain
• If you're using particularly cheap chains, they could wear faster than what is usual
• If you're running the chain dry too long, it could wear too fast due to lack of lubrication
• If you're oiling a chain too often, the large amount of oil continuously on chain surface could act as a fly paper, catching all dirt and carrying it to the chain innards, thus causing very rapid chain wear

I'm sure I will be heavily downvoted for linking into a heavily downvoted answer into a closed question, but with my chain care schedule, I get 4000 km wear life with very minimal effort spent on chain care.

Summary:

• Don't remove the factory lubricant from the chain, except maybe from only the surface of the chain using isopropanol. The factory lubricant is superior, far better than any lubricant you can apply at home.
• Wait until the chain starts to barely squeak until you lubricate it, it'll last 50 km of squeaking easily without causing too much wear; on dry conditions you should be getting 1000 km out of a single lubrication run. Early lubrication is number #1 chain wear cause, because a chain that isn't dry of oil has lots of road grit inside that continuously wears it away and with continuous lubrication you never let the grit possibility to get out of the innards of the chain. If you let it squeak very little, then there's no longer oil and the road grit won't be held by anything inside the chain. Just watch an old chain lubricated over 500 km ago. Its rollers are shiny clean. Letting the innards of the chain in the same condition mean they are shiny clean too.
• Brush the chain carefully to remove as much surface dirt as you can before lubricating it
• Use a thixotropic motorcycle chain lubricant in a spray can and remove the excess from the chain surface after distributing the lubricant, you can maybe help this surface lubricant removal with a rag very slightly moistened with small amount of isopropanol if you don't let the wet isopropanol reach the innards of the chain in large amounts
• Don't ever let the chain really squeak for hundreds of kilometers, that'll wear it away very soon

8-speed chains and cassettes are getting rare these days, my advice for chains is Shimano CN-HG71 and for cassettes CS-HG50 or CS-HG51. Don't use the cheap parts like CN-HG40, they likely wear too fast.

Answer 4

I had similar problem with new chain.

The entire drivetrain is, by convention, in bad shape: chainring and cassette worn, jockey pulley missing (consecutive!) teeth, rear derailluer slightly askew, and chain is stretched (>1%!). By all rights, the bike should be slipping like crazy, but it doesn't. It runs solidly and smoothly, like a champ!

So imagine my surprise when I replaced the chain with new-old-stock OEM chain, and the drivetrain began to grind and skip badly on the low gears and under light loads. Fortunately, restoring the old chain remedied the situation. So it seems my old, OEM comps are monogamous with my old worn out chain....until death do them part.