chainhwip

New cyclist here.

I've recently been told by my mechanic that I should have my chain replaced. He explained that because the chain and cassette "wear together", I may also need a new cassette if it does work with the new chain.

I'm currently running a 9-speed shimano sora set up and have not noticed any shifting or drive train issues after ~4000 miles.

Since there are plenty of affordable 9-speed chain/cassette options out there, would it make sense to just keep riding on what I have until I actually feel the need to replace the components?

Thanks

merlinextraligh

No. Chains are cheaper than cassettes. If you replace the chain when you're supposed to, you can go 4 chains or more before you need to replace the cassette.

Wait too long to replace the chain, and you have to replace the cassette, one to one.

You're also eating up your chainrings faster than you need to.

mkadam68

+1 Listen to this advice.

Replace the chain. Then do some brief intervals where you're stressing the gears, specifically the larger cogs in back (climb a short, steep hill or something). If you notice any skipping or other misalignment issues, yeah, might need to replace the cassette. The wear on the cassette can prematurely wear your chain as they force it to fit the worn out teeth of the cogs.

bikerjp

I went too long on my last chain and was told the same thing - may have worn the cassette too much. Put on a new chain and did some rides and everything is fine. Put on a new chain and do described above. If there's no skipping then you probably haven't worn the cassette yet. Might want to get a chain wear tool for the future.

Fox Farm

Keep the chain clean and lubed and you will get much more wear out of it. Not to mention that the bike will shift much better!

hhnngg1

Replace the chain, you should get 3-4 chains if replacing regularly for every cassette.

I'd recommend for you to buy a chain checking tool/ruler. They're super easy to use - basically a metal ruler, that if the two teeth drop in fully to the chain, the chain has been stretched and should be replaced. They cost like $8 or less and can warn you of your need to replace the chain before you wear the cassette.

As well, on the bright side, the Sora chains cost 50% of what the 105-Dura ace chains costs - they're like $30, and I found they don't last any less. (I have an ultegra bike as well.)

bigbadwullf

Just replaced the chain and cassette on my Cannondale Caffeine mtb. SRAM X7. $75 including the shop doing the work. Love my LBS!

hhnngg1

My Sora chain which I replaced last year after over 5,000 miles of use (it was still shifting no problem - just changed it because the chain checker showed it was exceeding the 1.0 mark) costed <$35 with tax at a pricey local LBS. Made me want to keep using Sora!

mprelaw

Find another mechanic. This one is looking to pick your pocket.

While he may be technically correct that they wear "together" in that each component is a wear and tear item, what he didn't add is that they do not wear at the same rate.

Bob Dopolina 

Incorrect.

@merlimextraligh nailed it in post #2.

merlinextraligh

What the mechanic told him was true. He may need to replace the cassette. The answer is whether it skips with a new chain, which appears to be what his mechanic was telling him.

mprelaw

I disagree. I don't think that a chain will wear enough in 4000 miles to warrant replacing the cassette. Especially if there are no signs of it when shifting.

merlinextraligh

1) depends on how it's been treated, and how it measures out. 4000 miles is a lot of miles for a 10 speed chain. The fact this was a 9 speed make it less likely that its gone way past spec.

2) the mechanic said he may need a new cassette. The proof is in the pudding.

3) the broader point is that you replace the chain before its measures past spec so that you don't have to replace the cassette.

Bob Dopolina 

Unlikely, yes, but always prudent to consider.

The tech was right; If a new chain skips on an old cassette it's time to replace the cassette. Odds are the OP won't have to.

mprelaw

With that, I do concur. I guess it was the whole "wear together" aspect of it that got me a little suspicious.

Bob Dopolina 

But they do wear together - as in at the same time and as a direct result of each other. How else would they wear?

chainhwip

Thanks for all the pointers.

If the current (old) chain is skip-free and there have been no shifting problems, does that suggest my cassette should be fine with a new chain?

How badly would riding on an "old" chain/cassette damage my chain rings?

Bob Dopolina 

The issue isn't skipping under load with the old chain/cassette. Once you replace the chain, if the new chain then skips under load on the old cassette you have used the chain too long, it has worn the cassette and now you need a new cassette as well.

merlinextraligh

It takes a long time to wear out chainrings on a road bike. So even if the chain is worn too far, you're not likely to do a lot of damage to the chainrings. My comment was in the context of the strategy of riding the old chain and cassette into the ground before replacing which would accelerate chainring wear to some degree.

DaveSSS 

That is a misconception. If the cogs are not worn enough to cause new-chain skip, then there will never be a problem using a new chain on the used cassette.

A new chain will just ride lower on the teeth than the old chain that was replaced.

cyclezen

My observations
9 spd chains (SRAM - Shimamno - KMC) seem to wear about the same as 7-8 spd - for me that's between 3.5 & 4K to the 1 % stretch point.
10 spd KMC/Shimano gives me about 2.5K, never over 3K - wipperman SO goes over 1% at 2K

chain stretch and cog wear is not an on/off thing. The more chain stretch the further/faster a cog will 'hook'.
smaller cogs are more prone to faster hooking than the karger ones. That said the cogs which seem to go 'first' are the 3, 4 and/or 5 (14 thru 16-17 depending...); because they are being used the most for time spent riding, when on either the big or small ring.
Badly worn cogs which still don't 'skip' when you put on a new chain, do cause faster stretching of the new chain. You're still riding/using the worn cog and new chain more than other gear combos...
I've found I lose on avg about 500-700 miles on a fresh chain used with a cogset where one or two cogs are worn badly, but not skipping.

you can replace any worn cog, without trashing the whole cassette. Cogs are available, and common replacement cogs, like Miche, work OK within a SHimnao cogset (wouldn;t know about new campy...)
MAny cassettes have their cogs 'pinned' together - those pins can be extracted (at least on the cogs below the last 3) , and the cogs split, and then individually replaced onto the hub carrier, loose (not repinned), with no problems; as long as the lock ring is snug. I've bought a couple of very lightly/bearly used cassettes, for cheap ($10-$20) from local riders who have 'changed' their cassettes, so that I have extra 14-17 cogs to use for replacement - I've used one 10 spd cog already...
At $65+ for a new Ultegra cassette, replacing a cog is cost effective for me.
my observations

surgeonstone

When Bob Dopp speaks, listen- an excellent source of cycling info.