Hi Guys,

I bought my dahon s18 road bike one month ago, I used it around 15 miles (25KM) a day Monday to Friday, I checked the chain length after two weeks of use, it indicates the chain not even close to 0.75% worn, but I just checked it today, after 4 weeks, it is already 1.% worn with totally less than 400 mils (650km). I take it to the shop, the guys says my chain and cassette has completely worn out, I need a new chain and cassette. But the bike never skip the cogs or feel anything strange.

My question is, how is it possible that the chain worn out so quickly in less than a month? do I need to replace cassette along with the chain or I could try new chain first and replace cassette afterward if the new chain doesn't fit well.

Also another question is that, my original cassette is 9 speed 11-25T, can I use 9 speed 12-25T instead? will it cause any issues?

Many thanks guys

Does not sound right. Make sure you have a good set of calipers to measure. If it's new a chain should last at least a few thousand Km.

You probably do NOT need to change your cassette unless it's really worn, most cassettes will last 3-4 chains. Going from 11-25 to 12-25 should not be a problem if you choose to get a new one.

Yes, all true. But if the chain IS that worn, it has likely ruined the cassette. Best to change both. So time for some questions. Was the chain well lubed? Was it clean or fouled with grit? Did you always ride cross-chained. I'm just looking for any reasonable explanation for the rapid wear.

The chain and cassette wear together to keep a good fit. But as the chain gets worse, it will start to wear the front rings. That is why you change chain and maybe cassette even before they start to skip.

Are you using the Park Tool chain measuring gadget or a ruler? I've seen the Park Tool chain measuring gadget indicate that chains are seriously worn when a ruler indicates that it's just fine.

Pin to pin is exactly 12" on a brand-new chain. Generally if you're replacing the chain before the 12 1/8" mark, you'll be ok. There's an excellent article here: https://www.sheldonbrown.com/chain-wear.html that explains in detail what's occurring.

I find it difficult to believe that you could ruin a chain in four weeks unless you were really trying

This is all very weird. What even lead you to check on a chain at 2 weeks and 4 weeks in to use?

If you have a brand-new bike and the shop tells you it is worn out after a month either you got robbed----or you are about to.

If you bought the bike used .... well, if it still works well, it doesn't need fixing, right?

I think it is well lubed, the only catch is that I got a set of tools to degrease and clean the chain then lubed it again. I might did it in a wrong way. the cogs looks very dirty now. I just bought a new set of cassette and chain, I will try it again and see if the same thing happens.

Do you think I need to lube my new chain and cassette before first ride?

I shouldn't get robbed I guess, I got my bike from somewhere else and it looks brand new, I measured the chain length myself, anyway, I got new cassette and chain and see what happened. Many thanks

No.

No.

Chain maintenance is one of those religious topics; i.e., the "correct" way to clean a chain, the "correct" lubricant to use, the "correct" frequency to clean the chain, etc.

I'm convinced that whatever chain maintenance routine you use is better than doing nothing. Chains -- like any moving parts -- need to be cleaned and lubricated periodically. It's a fact of life that your tires will kick up dirt and that dirt sticks to the lubricant, thus making it look dirty again, generally very soon after you cleaned it.

New chains come with factory lubricant that is generally better than anything you could have put on yourself because the factory can get the lubricant where it actually needs to be -- on the inside. Don't touch it; just install it and ride.

Again -- unless you cleaned a new chain with a sandblaster, there is no possible way you wrecked it within a two week span.

My question to OP is how does the bike ride? Would have noticed that it needs a new cassette and chain if you hadn't measured it and if you hadn't taken it to the LBS? If not, just keep riding until you notice that something is 'off'.

Along with the previous no's, I'll add that you don't lube the cassette at all.

I don't believe this is necessarily true.

KMC chain I recently bought was covered with some kind of sticky goop that sure didn't impress me as a lubricant. However Shimano chains feel more like oil.

More research needed but common sense tells me the chains are coated to prevent rust/extend shelf life which may or may not be on optimal lubricant.

Anyway, I stripped the goop off and lubed it myself.

I also disagree and will say using a good chain lube, it will definitely "get where it needs to go". I put a drop on every link rather than just running a chain across dripping bottle.

Regardless of debate, fact is, the factory lube is gone the first time you clean your chain, which for me is about every 100 miles so if in doubt, there is not much advantage in leaving whatever coating is on the chain new.

There are whole threads on this.

The factory lubricant is very good lube. Its put on before the chain is assembled. The "stickiness" is not really an issue, unless you're riding in very dusty conditions.

Both Shimano, and Sheldon say its the best lubricant available, and you shouldn't strip it off.

As for replacing the cassette, I doubt the cassette is trashed in 400 miles. I'd put a new chain on. If it doesn't skip, no need for a new cassette. If it skips, put on a new cassette.

Other option if the bike is still shifting ok, keep running the chain until it no longer does. Both cassette and chain will wear in together. The cassette will be toast when you eventually change the chain, and you'll need to replace both chain and cassette.

Normally, you can get 3-4 chains to one cassette, so the running it in to the ground approach is not cost effective, but if you think the cassette is already significantly worn, then keeping running both is a viable option, as long as the bike is shifting well.

As I said above, chain maintenance is a religious debate. I'm not familiar with KMC chains as I always use SRAM chains. SRAM chains feel sticky when new as well. According to reps from Campagnolo, Shimano and SRAM though (see here: Chain maintenance advice from the experts | Road Bike News, Reviews, and Photos), what a new chain comes with is "the good stuff".

As you said though -- the first time you clean the chain the factory lube probably removes the factory lube. I clean my chain once a week or so which is usually around 150 miles.