Sorry, assume this has been done to death but can’t find it for some reason in the search….

What exactly is the problem with a new chain on an old cassette and chain rings? If I just replace the chain will it really be a disaster/pointless compared to replacing the whole lot?

Reckon my chain is coming to the end of it’s use but everything else looks OK. Trying to save money but willing to be advised if it’s false economy

if the cassette is badly worn it will not work the chain will skip on the cassette, and the result will be impaling your knee or worse your balls on the stem.

If the cassette isn’t worn then you’ll be fine.

Measure the length of the chain or get a checker.

new chain on an old cassette and chain rings

= chainsuck.

Which is both a PITA and ride stopping.

Better to either
A: run what you have into the ground
B: change the chain before if gets to 0.75% worn and prolong life.

/Edit – Sorry that may not appear very helpful, but depending on how worn your original chain was – that pretty much determines your viable options. Med / long term – buy a chain checker (£5 ish) and use it regularish.

It’s a conspiracy by bikeshops/manufacturers/aliens to make you spend more money and you’re the only person to see through it.
Go for it and prove them all wrong.

Generally – 3 chains before cassette and chain ring change

Generally – 3 chains before cassette and chain ring change

I agree Jota – but – BIG BUT – only if the 3 chains arent allowed to get totally knackered.

Yup – I change when the gauge reads 1.0

I buy the 3 chains up front & swap them regularly. With alu Chainrings I’ve found you can wear them down to almost stupid levels using this method. However if the middle and granny are steel the chains will start snapping and giving up the ghost long before the Chainrings are done.

Try it and see if it slips or sucks. If it does, buy a new cassette too, if not then it’s fine. Simples.

Worn cassette and new chain will generate skipping and the chain slipping over the cassette.

Testing the (cheapskate, don’t replace the cassette theory) the other day resulted in a heavy exit through the front door. Scabs on face an arm that doesn’t work and not going to Scotland on a trip I organised!

Chain was worn marginally beyond 1.0!

Up to you though!!