How do you know when cassette/chain rings are cuffed?

[Disastrous]

I'm sure mine are nowhere near, as the bike seems to ride fine, but how do you know when you need new ones??

Does the bike start misbehaving in some way?

[BMWBen]

You need to measure the chain stretch with one of these:

http://www.probikekit.co.uk/bicycle-tools-and-main...

Once it gets stretched enough for the tool to drop into the chain, it's time to think about changing. If both sides of the tool will fit, then you're overdue.

[Jimbo.]

Disastrous said:

I'm sure mine are nowhere near, as the bike seems to ride fine, but how do you know when you need new ones??

Does the bike start misbehaving in some way?

Your shifting will go to st, maybe dropped chains etc, etc. Look at the teeth on the cassette and chainrings: if they're of a "sharks fin" profile, then they're goosed. Harder to tell with the chainrings due to their odd shapes (intentional, to aid shifting).

[IroningMan]

As above: measure the chain wear: if it's 0.75% then replace the chain. If it's over 1% then expect the cassette to be worn, too.

Fit a new chain; if it seems to 'jump' at the back then you need a new cassette. (Unless the chain has a tight spot where you've joined it.) If it 'sucks', ie stays hooked-up when it should run smoothly off the bottom of the chainring, then you need a new chainring.

One chainring should see out between two and four cassettes, each cassette should see out at least two chains.

All rules of thumb - others' experience may vary, your investment may go down etc...

[Engineer1]

A above except if it's a mountain bike additional damage from grit and trips ino the scenery can add to wear.

[yellowjack]

IroningMan said:

As above: measure the chain wear: if it's 0.75% then replace the chain. If it's over 1% then expect the cassette to be worn, too.

Fit a new chain; if it seems to 'jump' at the back then you need a new cassette. (Unless the chain has a tight spot where you've joined it.) If it 'sucks', ie stays hooked-up when it should run smoothly off the bottom of the chainring, then you need a new chainring.

One chainring should see out between two and four cassettes, each cassette should see out at least two chains.

All rules of thumb - others' experience may vary, your investment may go down etc...

What 'im said. This has been pretty much my experience too. I don't agree with the nutters who say you need a new cassette every time you swap a chain. I use a Park Tools Chain Checker tool http://compare.ebay.co.uk/like/130810721046?var=lv... which I keep handy in the garage. It takes seconds to check a chain once a week or so, and you should catch the chain before it's totally jiffed, thereby saving you from needing a new cassette every time. Keeping the chain clean and lubricated will extend the life of it somewhat, but wear is inevitable. Don't be tempted to keep riding a worn chain - it'll get very expensive very quickly if you do, and it's a false economy.

[Disastrous]

Thanks all. Much like a motorbike then, which makes sense I guess!

Will pick up a chain checker next time I'm in the bike shop.

Cheers!

[rhinochopig]

One thing I would add. If it's at >1% stretch when you check it, I would simply carry on using it until the whole drive chain is shot. At >1% the chain and cassette are, in all likelihood, fully mated so will require the replacement of chain and cassette, and in may well need a front ring or two as well.

If it's not jumping at >1% you can usually keep going with the drive-train until the teeth look like sharks teeth before you get any problems. It'll postpone the cost of the new bits considerably. Oh and if you ever need 2 or more rings replacing and are running a low to middle range groupset on an MTB it's usually more cost effective to buy a new crankset as the chances are the BB bearings will be worn too.