Is this cassette worn out?

I use a chain tool checker too, but they don't actually measure chain wear correctly. I was convinced by this explanation (with pictures!): http://pardo.net/bike/pic/fail-004/000.html

Agreed, I don't get this whole 'chain checkers don't measure the right thing' argument. If you take a chain at 0.75% wear measured the 'correct' way and then make a go/no go tool to just fit through that chain then it's good enough for 99% of people, surely?

As others note, check your chain. If it's worn (and it's similar age to the cassette) then it's likely the cassette is worn too (even if it doesn't look it (it doesn't)). 

Trick is to replace your chain before it wears so much that the cassette much that the cassette won't play nice with a new chain. The two will wear together while still performing OK but get to a point where they both need replaced. Better change the chain earlier and prolong the life of the cassette*.

A chain checker is a good investment in the long run.

* not that I bother with any of this good practice myself - I just run the f**kers into the ground and then change the lot** (maybe a chainring too)

** there's a reason I haven't gone 11 speed...

Thanks KiwiMike, I bow to your superior knowledge and experience in these matters.

Get a new chain and cassette and buy a new chain to give you a good starting point and then look on ebay for joining links (I bought a pack of 5 KMC links for about £5 recently).  Keep your eyes open for sales on chains and change your chain twice a year, total cost will work out to be about £25 a year and dont forget that the joining links do need changing ocassionally.  As others have said, 3 or 4 chains per cassette (a "rule of thumb" is only a guess so lots of winter/mucky riding will increase wear rate) and as for the comment that a chain will only jump on small sprockets, that is the most stupid statement spouted on this topic so far.

I tend to change chains and cassettes together for worry free cycling.  You can get an 11spd 105 for 30 quid online or your LBS will pricematch*. Feels nicer too.  Admittedly,  1600 kms isn't much, but poor weather conditions and a worn chain could do it. 

It seems that your instinct is not to trust your LBS.  If so, just test-ride the old cassette; put it under stress, and then decide. 

*I wouldn't do this to an independent LBS

LBS = Taking the piss, the cassette on my daily once its cleaned up is probably not much different, admittedly it's a 10 speed tiagra so different material but it's done 5000 miles and not a hint of slippage.

Suggest you find another shop IMHO because they'll probably be taking the piss with other punters not in the know 

They shouldnt take the piss like this. Basically fit a new chain, ride up the road, give it some beans. If it skips, new cassette needed as well. If not, then its fine.

Completely worn out. Replace it immediately, I can take care for recycling this worn out piece of kit though...

If your chain had worn to over 1% that may mean that your casette is worn too, however you choose to measure it.  Rohloff do sell a casette wear indicating tool (kind of ironic) but seems very subjective in use, I haven't got one but tempted.

The only real test is fitting a new chain, if it skips on the smaller cogs when you lay down the power, you need a new one.

Chain rings tend to get pointy as they wear, so do jockey wheels.

I agree with DaSy.

Presumably, you took your bike to your LBS because they have more experience than you about this kind of thing, so it doesn't make much sense to second-guess them for relatively cheap consumable parts.

I'd recommend going along with their recommendation, but ask for the "old" cassette. Then, you can muck around with swapping the old cassette and see if you get any issues with slipping gears and verify if your LBS was taking you for a ride or not.

That cassette looks very slightly used but really minimal wear as I can see.

I've heard it said that says you shoud change the cassette and chain at the same time... but looking at that cassette that could only be a call that this mechanic would have taken without actually looking at your cassette. (I don't adhere to that by the way)

It's dead easy to change a cassette yourself really a three min job.

What was the situation that caused the bike shop to say it needed replacing? I assume you took it to the shop for a reason.

If you zoom to max, you can see wear on the 22, 25 and 28 cogs, whether it is enough to cause it to skip with a new chain could only be told by actually trying it. I used to get lots of cassettes in the shop that looked okay but acted dreadfully when given a new chain. 

It looks terrible on the shop if you service a bike, put on a new chain and give it a quick test and all looks good, only for the customer to take it out on a big ride, crank it hard on the first big hill and the chain to jump a tooth and send the riders knackers onto the top-tube. This tends to make you say that if the chain is more than just slightly worn, then you need a cassette too.

It only has to be one cog that has excessive wear (and usually is, as there tends to be a gear you spend the most time in) for the cassette to need replacing (you can swap out some individual or clusters of cogs but it is rarely cost-effective).

I change my chains before I can get the .5 % tooth of a Park chain checker in, if it goes past that then a new cassette goes on.

Most LBSs aren't making enough money on a cassette to risk their reputation on blagging bits for the sake of it. Experience tells you you are better off changing cassette and chain if there is any wear on the chain, or leaving them as is. It is a difficult call quite often for a shop.

Your LBS is using you to make a quick buck. Fuck em. Buy the bits you need on line and do the work yourself. 

Looks almost new to me.

That looks fine to me and at only 1600km/1000 miles it's barely used.  

I got replace a chain a year on my good bike, 2500 outdoor miles and time on the kickr.  I keep checking with the chain checker so I don't let it get too stretched.  

I recently changed my cassette, it had seen 4 chains used with it.  It looked fine, it wasn't slipping but on certain gears it wouldn't change up the cassette.  I checked what I could, adjusted the B Screw but it never improved, Di2 so not cables stretching.  

Now with the new cassette it is fine, no other adjustments.  So the above 3 chains to a cassette seems about right.  

Brian, that looks fine to me. 

Here's a rule of thumb: for every three chains, replace the cogset. For every two cogsets, replace the chainrings.

You can easily check a chain with a ruler or preferably digital calipers. A new chain measures 127mm for 5 links new. At 127.4, look to replace it. If you go beyond 127.5, you've prematurely worn the cogs and will suffer accellerated chain wear.

A decent chain should last you 5,000 miles. Ish. so after 15,000 miles you're up for a total of 3 chains at £10 each + cogset say £30 - or £0.4p/mile.

Nothing wrong with it, they’re pulling your pants down. Take your business elsewhere. 

That's perfectly true but I will chip in that the cassette in the picture looks practically brand new.

Put a new chain on and ride it.  If the chain skips on worn gears, the cassette is worn out.